up follow livre

venv/lib/python3.13/site-packages/scipy/optimize/tests/_cython_examples/extending.pyx

@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+#cython: language_level=3
+#cython: boundscheck=False
+#cython: wraparound=False
+"""
+Taken from docstring for scipy.optimize.cython_optimize module.
+"""
+
+from scipy.optimize.cython_optimize cimport brentq
+
+# import math from Cython
+from libc cimport math
+
+myargs = {'C0': 1.0, 'C1': 0.7}  # a dictionary of extra arguments
+XLO, XHI = 0.5, 1.0  # lower and upper search boundaries
+XTOL, RTOL, MITR = 1e-3, 1e-3, 10  # other solver parameters
+
+# user-defined struct for extra parameters
+ctypedef struct test_params:
+    double C0
+    double C1
+
+
+# user-defined callback
+cdef double f(double x, void *args) noexcept:
+    cdef test_params *myargs = <test_params *> args
+    return myargs.C0 - math.exp(-(x - myargs.C1))
+
+
+# Cython wrapper function
+cdef double brentq_wrapper_example(dict args, double xa, double xb,
+                                    double xtol, double rtol, int mitr):
+    # Cython automatically casts dictionary to struct
+    cdef test_params myargs = args
+    return brentq(
+        f, xa, xb, <test_params *> &myargs, xtol, rtol, mitr, NULL)
+
+
+# Python function
+def brentq_example(args=myargs, xa=XLO, xb=XHI, xtol=XTOL, rtol=RTOL,
+                    mitr=MITR):
+    '''Calls Cython wrapper from Python.'''
+    return brentq_wrapper_example(args, xa, xb, xtol, rtol, mitr)

venv/lib/python3.13/site-packages/scipy/optimize/tests/_cython_examples/meson.build

@@ -0,0 +1,32 @@
+project('random-build-examples', 'c', 'cpp', 'cython')
+
+fs = import('fs')
+
+py3 = import('python').find_installation(pure: false)
+
+cy = meson.get_compiler('cython')
+
+if not cy.version().version_compare('>=3.0.8')
+  error('tests requires Cython >= 3.0.8')
+endif
+
+cython_args = []
+if cy.version().version_compare('>=3.1.0')
+  cython_args += ['-Xfreethreading_compatible=True']
+endif
+
+py3.extension_module(
+  'extending',
+  'extending.pyx',
+  cython_args: cython_args,
+  install: false,
+)
+
+extending_cpp = fs.copyfile('extending.pyx', 'extending_cpp.pyx')
+py3.extension_module(
+  'extending_cpp',
+  extending_cpp,
+  cython_args: cython_args,
+  install: false,
+  override_options : ['cython_language=cpp']
+)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test__basinhopping.py

@@ -0,0 +1,535 @@
+"""
+Unit tests for the basin hopping global minimization algorithm.
+"""
+import copy
+
+from numpy.testing import (assert_almost_equal, assert_equal, assert_,
+                           assert_allclose)
+import pytest
+from pytest import raises as assert_raises
+import numpy as np
+from numpy import cos, sin
+
+from scipy.optimize import basinhopping, OptimizeResult
+from scipy.optimize._basinhopping import (
+    Storage, RandomDisplacement, Metropolis, AdaptiveStepsize)
+
+
+def func1d(x):
+    f = cos(14.5 * x - 0.3) + (x + 0.2) * x
+    df = np.array(-14.5 * sin(14.5 * x - 0.3) + 2. * x + 0.2)
+    return f, df
+
+
+def func2d_nograd(x):
+    f = cos(14.5 * x[0] - 0.3) + (x[1] + 0.2) * x[1] + (x[0] + 0.2) * x[0]
+    return f
+
+
+def func2d(x):
+    f = cos(14.5 * x[0] - 0.3) + (x[1] + 0.2) * x[1] + (x[0] + 0.2) * x[0]
+    df = np.zeros(2)
+    df[0] = -14.5 * sin(14.5 * x[0] - 0.3) + 2. * x[0] + 0.2
+    df[1] = 2. * x[1] + 0.2
+    return f, df
+
+
+def func2d_easyderiv(x):
+    f = 2.0*x[0]**2 + 2.0*x[0]*x[1] + 2.0*x[1]**2 - 6.0*x[0]
+    df = np.zeros(2)
+    df[0] = 4.0*x[0] + 2.0*x[1] - 6.0
+    df[1] = 2.0*x[0] + 4.0*x[1]
+
+    return f, df
+
+
+class MyTakeStep1(RandomDisplacement):
+    """use a copy of displace, but have it set a special parameter to
+    make sure it's actually being used."""
+    def __init__(self):
+        self.been_called = False
+        super().__init__()
+
+    def __call__(self, x):
+        self.been_called = True
+        return super().__call__(x)
+
+
+def myTakeStep2(x):
+    """redo RandomDisplacement in function form without the attribute stepsize
+    to make sure everything still works ok
+    """
+    s = 0.5
+    x += np.random.uniform(-s, s, np.shape(x))
+    return x
+
+
+class MyAcceptTest:
+    """pass a custom accept test
+
+    This does nothing but make sure it's being used and ensure all the
+    possible return values are accepted
+    """
+    def __init__(self):
+        self.been_called = False
+        self.ncalls = 0
+        self.testres = [False, 'force accept', True, np.bool_(True),
+                        np.bool_(False), [], {}, 0, 1]
+
+    def __call__(self, **kwargs):
+        self.been_called = True
+        self.ncalls += 1
+        if self.ncalls - 1 < len(self.testres):
+            return self.testres[self.ncalls - 1]
+        else:
+            return True
+
+
+class MyCallBack:
+    """pass a custom callback function
+
+    This makes sure it's being used. It also returns True after 10
+    steps to ensure that it's stopping early.
+
+    """
+    def __init__(self):
+        self.been_called = False
+        self.ncalls = 0
+
+    def __call__(self, x, f, accepted):
+        self.been_called = True
+        self.ncalls += 1
+        if self.ncalls == 10:
+            return True
+
+
+class TestBasinHopping:
+
+    def setup_method(self):
+        """ Tests setup.
+
+        Run tests based on the 1-D and 2-D functions described above.
+        """
+        self.x0 = (1.0, [1.0, 1.0])
+        self.sol = (-0.195, np.array([-0.195, -0.1]))
+
+        self.tol = 3  # number of decimal places
+
+        self.niter = 100
+        self.disp = False
+
+        self.kwargs = {"method": "L-BFGS-B", "jac": True}
+        self.kwargs_nograd = {"method": "L-BFGS-B"}
+
+    def test_TypeError(self):
+        # test the TypeErrors are raised on bad input
+        i = 1
+        # if take_step is passed, it must be callable
+        assert_raises(TypeError, basinhopping, func2d, self.x0[i],
+                      take_step=1)
+        # if accept_test is passed, it must be callable
+        assert_raises(TypeError, basinhopping, func2d, self.x0[i],
+                      accept_test=1)
+
+    def test_input_validation(self):
+        msg = 'target_accept_rate has to be in range \\(0, 1\\)'
+        with assert_raises(ValueError, match=msg):
+            basinhopping(func1d, self.x0[0], target_accept_rate=0.)
+        with assert_raises(ValueError, match=msg):
+            basinhopping(func1d, self.x0[0], target_accept_rate=1.)
+
+        msg = 'stepwise_factor has to be in range \\(0, 1\\)'
+        with assert_raises(ValueError, match=msg):
+            basinhopping(func1d, self.x0[0], stepwise_factor=0.)
+        with assert_raises(ValueError, match=msg):
+            basinhopping(func1d, self.x0[0], stepwise_factor=1.)
+
+    def test_1d_grad(self):
+        # test 1-D minimizations with gradient
+        i = 0
+        res = basinhopping(func1d, self.x0[i], minimizer_kwargs=self.kwargs,
+                           niter=self.niter, disp=self.disp)
+        assert_almost_equal(res.x, self.sol[i], self.tol)
+
+    def test_2d(self):
+        # test 2d minimizations with gradient
+        i = 1
+        res = basinhopping(func2d, self.x0[i], minimizer_kwargs=self.kwargs,
+                           niter=self.niter, disp=self.disp)
+        assert_almost_equal(res.x, self.sol[i], self.tol)
+        assert_(res.nfev > 0)
+
+    def test_njev(self):
+        # test njev is returned correctly
+        i = 1
+        minimizer_kwargs = self.kwargs.copy()
+        # L-BFGS-B doesn't use njev, but BFGS does
+        minimizer_kwargs["method"] = "BFGS"
+        res = basinhopping(func2d, self.x0[i],
+                           minimizer_kwargs=minimizer_kwargs, niter=self.niter,
+                           disp=self.disp)
+        assert_(res.nfev > 0)
+        assert_equal(res.nfev, res.njev)
+
+    def test_jac(self):
+        # test Jacobian returned
+        minimizer_kwargs = self.kwargs.copy()
+        # BFGS returns a Jacobian
+        minimizer_kwargs["method"] = "BFGS"
+
+        res = basinhopping(func2d_easyderiv, [0.0, 0.0],
+                           minimizer_kwargs=minimizer_kwargs, niter=self.niter,
+                           disp=self.disp)
+
+        assert_(hasattr(res.lowest_optimization_result, "jac"))
+
+        # in this case, the Jacobian is just [df/dx, df/dy]
+        _, jacobian = func2d_easyderiv(res.x)
+        assert_almost_equal(res.lowest_optimization_result.jac, jacobian,
+                            self.tol)
+
+    def test_2d_nograd(self):
+        # test 2-D minimizations without gradient
+        i = 1
+        res = basinhopping(func2d_nograd, self.x0[i],
+                           minimizer_kwargs=self.kwargs_nograd,
+                           niter=self.niter, disp=self.disp)
+        assert_almost_equal(res.x, self.sol[i], self.tol)
+
+    @pytest.mark.fail_slow(10)
+    def test_all_minimizers(self):
+        # Test 2-D minimizations with gradient. Nelder-Mead, Powell, COBYLA, and
+        # COBYQA don't accept jac=True, so aren't included here.
+        i = 1
+        methods = ['CG', 'BFGS', 'Newton-CG', 'L-BFGS-B', 'TNC', 'SLSQP']
+        minimizer_kwargs = copy.copy(self.kwargs)
+        for method in methods:
+            minimizer_kwargs["method"] = method
+            res = basinhopping(func2d, self.x0[i],
+                               minimizer_kwargs=minimizer_kwargs,
+                               niter=self.niter, disp=self.disp)
+            assert_almost_equal(res.x, self.sol[i], self.tol)
+
+    @pytest.mark.fail_slow(40)
+    def test_all_nograd_minimizers(self):
+        # Test 2-D minimizations without gradient. Newton-CG requires jac=True,
+        # so not included here.
+        i = 1
+        methods = ['CG', 'BFGS', 'L-BFGS-B', 'TNC', 'SLSQP',
+                   'Nelder-Mead', 'Powell', 'COBYLA', 'COBYQA']
+        minimizer_kwargs = copy.copy(self.kwargs_nograd)
+        for method in methods:
+            # COBYQA takes extensive amount of time on this problem
+            niter = 10 if method == 'COBYQA' else self.niter
+            minimizer_kwargs["method"] = method
+            res = basinhopping(func2d_nograd, self.x0[i],
+                               minimizer_kwargs=minimizer_kwargs,
+                               niter=niter, disp=self.disp, seed=1234)
+            tol = self.tol
+            if method == 'COBYLA':
+                tol = 2
+            assert_almost_equal(res.x, self.sol[i], decimal=tol)
+
+    def test_pass_takestep(self):
+        # test that passing a custom takestep works
+        # also test that the stepsize is being adjusted
+        takestep = MyTakeStep1()
+        initial_step_size = takestep.stepsize
+        i = 1
+        res = basinhopping(func2d, self.x0[i], minimizer_kwargs=self.kwargs,
+                           niter=self.niter, disp=self.disp,
+                           take_step=takestep)
+        assert_almost_equal(res.x, self.sol[i], self.tol)
+        assert_(takestep.been_called)
+        # make sure that the build in adaptive step size has been used
+        assert_(initial_step_size != takestep.stepsize)
+
+    def test_pass_simple_takestep(self):
+        # test that passing a custom takestep without attribute stepsize
+        takestep = myTakeStep2
+        i = 1
+        res = basinhopping(func2d_nograd, self.x0[i],
+                           minimizer_kwargs=self.kwargs_nograd,
+                           niter=self.niter, disp=self.disp,
+                           take_step=takestep)
+        assert_almost_equal(res.x, self.sol[i], self.tol)
+
+    def test_pass_accept_test(self):
+        # test passing a custom accept test
+        # makes sure it's being used and ensures all the possible return values
+        # are accepted.
+        accept_test = MyAcceptTest()
+        i = 1
+        # there's no point in running it more than a few steps.
+        basinhopping(func2d, self.x0[i], minimizer_kwargs=self.kwargs,
+                     niter=10, disp=self.disp, accept_test=accept_test)
+        assert_(accept_test.been_called)
+
+    def test_pass_callback(self):
+        # test passing a custom callback function
+        # This makes sure it's being used. It also returns True after 10 steps
+        # to ensure that it's stopping early.
+        callback = MyCallBack()
+        i = 1
+        # there's no point in running it more than a few steps.
+        res = basinhopping(func2d, self.x0[i], minimizer_kwargs=self.kwargs,
+                           niter=30, disp=self.disp, callback=callback)
+        assert_(callback.been_called)
+        assert_("callback" in res.message[0])
+        # One of the calls of MyCallBack is during BasinHoppingRunner
+        # construction, so there are only 9 remaining before MyCallBack stops
+        # the minimization.
+        assert_equal(res.nit, 9)
+
+    def test_minimizer_fail(self):
+        # test if a minimizer fails
+        i = 1
+        self.kwargs["options"] = dict(maxiter=0)
+        self.niter = 10
+        res = basinhopping(func2d, self.x0[i], minimizer_kwargs=self.kwargs,
+                           niter=self.niter, disp=self.disp)
+        # the number of failed minimizations should be the number of
+        # iterations + 1
+        assert_equal(res.nit + 1, res.minimization_failures)
+
+    def test_niter_zero(self):
+        # gh5915, what happens if you call basinhopping with niter=0
+        i = 0
+        basinhopping(func1d, self.x0[i], minimizer_kwargs=self.kwargs,
+                     niter=0, disp=self.disp)
+
+    def test_rng_reproducibility(self):
+        # rng should ensure reproducibility between runs
+        minimizer_kwargs = {"method": "L-BFGS-B", "jac": True}
+
+        f_1 = []
+
+        def callback(x, f, accepted):
+            f_1.append(f)
+
+        basinhopping(func2d, [1.0, 1.0], minimizer_kwargs=minimizer_kwargs,
+                     niter=10, callback=callback, rng=10)
+
+        f_2 = []
+
+        def callback2(x, f, accepted):
+            f_2.append(f)
+
+        basinhopping(func2d, [1.0, 1.0], minimizer_kwargs=minimizer_kwargs,
+                     niter=10, callback=callback2, rng=10)
+        assert_equal(np.array(f_1), np.array(f_2))
+
+    def test_random_gen(self):
+        # check that np.random.Generator can be used (numpy >= 1.17)
+        rng = np.random.default_rng(1)
+
+        minimizer_kwargs = {"method": "L-BFGS-B", "jac": True}
+
+        res1 = basinhopping(func2d, [1.0, 1.0],
+                            minimizer_kwargs=minimizer_kwargs,
+                            niter=10, rng=rng)
+
+        rng = np.random.default_rng(1)
+        res2 = basinhopping(func2d, [1.0, 1.0],
+                            minimizer_kwargs=minimizer_kwargs,
+                            niter=10, rng=rng)
+        assert_equal(res1.x, res2.x)
+
+    def test_monotonic_basin_hopping(self):
+        # test 1-D minimizations with gradient and T=0
+        i = 0
+
+        res = basinhopping(func1d, self.x0[i], minimizer_kwargs=self.kwargs,
+                           niter=self.niter, disp=self.disp, T=0)
+        assert_almost_equal(res.x, self.sol[i], self.tol)
+
+
+@pytest.mark.thread_unsafe
+class Test_Storage:
+    def setup_method(self):
+        self.x0 = np.array(1)
+        self.f0 = 0
+
+        minres = OptimizeResult(success=True)
+        minres.x = self.x0
+        minres.fun = self.f0
+
+        self.storage = Storage(minres)
+
+    def test_higher_f_rejected(self):
+        new_minres = OptimizeResult(success=True)
+        new_minres.x = self.x0 + 1
+        new_minres.fun = self.f0 + 1
+
+        ret = self.storage.update(new_minres)
+        minres = self.storage.get_lowest()
+        assert_equal(self.x0, minres.x)
+        assert_equal(self.f0, minres.fun)
+        assert_(not ret)
+
+    @pytest.mark.parametrize('success', [True, False])
+    def test_lower_f_accepted(self, success):
+        new_minres = OptimizeResult(success=success)
+        new_minres.x = self.x0 + 1
+        new_minres.fun = self.f0 - 1
+
+        ret = self.storage.update(new_minres)
+        minres = self.storage.get_lowest()
+        assert (self.x0 != minres.x) == success  # can't use `is`
+        assert (self.f0 != minres.fun) == success  # left side is NumPy bool
+        assert ret is success
+
+
+class Test_RandomDisplacement:
+    def setup_method(self):
+        self.stepsize = 1.0
+        self.N = 300000
+
+    def test_random(self):
+        # the mean should be 0
+        # the variance should be (2*stepsize)**2 / 12
+        # note these tests are random, they will fail from time to time
+        rng = np.random.RandomState(0)
+        x0 = np.zeros([self.N])
+        displace = RandomDisplacement(stepsize=self.stepsize, rng=rng)
+        x = displace(x0)
+        v = (2. * self.stepsize) ** 2 / 12
+        assert_almost_equal(np.mean(x), 0., 1)
+        assert_almost_equal(np.var(x), v, 1)
+
+
+class Test_Metropolis:
+    def setup_method(self):
+        self.T = 2.
+        self.met = Metropolis(self.T)
+        self.res_new = OptimizeResult(success=True, fun=0.)
+        self.res_old = OptimizeResult(success=True, fun=1.)
+
+    def test_boolean_return(self):
+        # the return must be a bool, else an error will be raised in
+        # basinhopping
+        ret = self.met(res_new=self.res_new, res_old=self.res_old)
+        assert isinstance(ret, bool)
+
+    def test_lower_f_accepted(self):
+        assert_(self.met(res_new=self.res_new, res_old=self.res_old))
+
+    def test_accept(self):
+        # test that steps are randomly accepted for f_new > f_old
+        one_accept = False
+        one_reject = False
+        for i in range(1000):
+            if one_accept and one_reject:
+                break
+            res_new = OptimizeResult(success=True, fun=1.)
+            res_old = OptimizeResult(success=True, fun=0.5)
+            ret = self.met(res_new=res_new, res_old=res_old)
+            if ret:
+                one_accept = True
+            else:
+                one_reject = True
+        assert_(one_accept)
+        assert_(one_reject)
+
+    def test_GH7495(self):
+        # an overflow in exp was producing a RuntimeWarning
+        # create own object here in case someone changes self.T
+        met = Metropolis(2)
+        res_new = OptimizeResult(success=True, fun=0.)
+        res_old = OptimizeResult(success=True, fun=2000)
+        with np.errstate(over='raise'):
+            met.accept_reject(res_new=res_new, res_old=res_old)
+
+    def test_gh7799(self):
+        # gh-7799 reported a problem in which local search was successful but
+        # basinhopping returned an invalid solution. Show that this is fixed.
+        def func(x):
+            return (x**2-8)**2+(x+2)**2
+
+        x0 = -4
+        limit = 50  # Constrain to func value >= 50
+        con = {'type': 'ineq', 'fun': lambda x: func(x) - limit},
+        res = basinhopping(
+            func,
+            x0,
+            30,
+            seed=np.random.RandomState(1234),
+            minimizer_kwargs={'constraints': con}
+        )
+        assert res.success
+        assert_allclose(res.fun, limit, rtol=1e-6)
+
+    def test_accept_gh7799(self):
+        # Metropolis should not accept the result of an unsuccessful new local
+        # search if the old local search was successful
+
+        met = Metropolis(0)  # monotonic basin hopping
+        res_new = OptimizeResult(success=True, fun=0.)
+        res_old = OptimizeResult(success=True, fun=1.)
+
+        # if new local search was successful and energy is lower, accept
+        assert met(res_new=res_new, res_old=res_old)
+        # if new res is unsuccessful, don't accept - even if energy is lower
+        res_new.success = False
+        assert not met(res_new=res_new, res_old=res_old)
+        # ...unless the old res was unsuccessful, too. In that case, why not?
+        res_old.success = False
+        assert met(res_new=res_new, res_old=res_old)
+
+    def test_reject_all_gh7799(self):
+        # Test the behavior when there is no feasible solution
+        def fun(x):
+            return x@x
+
+        def constraint(x):
+            return x + 1
+
+        kwargs = {'constraints': {'type': 'eq', 'fun': constraint},
+                  'bounds': [(0, 1), (0, 1)], 'method': 'slsqp'}
+        res = basinhopping(fun, x0=[2, 3], niter=10, minimizer_kwargs=kwargs)
+        assert not res.success
+
+
+class Test_AdaptiveStepsize:
+    def setup_method(self):
+        self.stepsize = 1.
+        self.ts = RandomDisplacement(stepsize=self.stepsize)
+        self.target_accept_rate = 0.5
+        self.takestep = AdaptiveStepsize(takestep=self.ts, verbose=False,
+                                         accept_rate=self.target_accept_rate)
+
+    def test_adaptive_increase(self):
+        # if few steps are rejected, the stepsize should increase
+        x = 0.
+        self.takestep(x)
+        self.takestep.report(False)
+        for i in range(self.takestep.interval):
+            self.takestep(x)
+            self.takestep.report(True)
+        assert_(self.ts.stepsize > self.stepsize)
+
+    def test_adaptive_decrease(self):
+        # if few steps are rejected, the stepsize should increase
+        x = 0.
+        self.takestep(x)
+        self.takestep.report(True)
+        for i in range(self.takestep.interval):
+            self.takestep(x)
+            self.takestep.report(False)
+        assert_(self.ts.stepsize < self.stepsize)
+
+    def test_all_accepted(self):
+        # test that everything works OK if all steps were accepted
+        x = 0.
+        for i in range(self.takestep.interval + 1):
+            self.takestep(x)
+            self.takestep.report(True)
+        assert_(self.ts.stepsize > self.stepsize)
+
+    def test_all_rejected(self):
+        # test that everything works OK if all steps were rejected
+        x = 0.
+        for i in range(self.takestep.interval + 1):
+            self.takestep(x)
+            self.takestep.report(False)
+        assert_(self.ts.stepsize < self.stepsize)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test__dual_annealing.py

@@ -0,0 +1,416 @@
+# Dual annealing unit tests implementation.
+# Copyright (c) 2018 Sylvain Gubian <sylvain.gubian@pmi.com>,
+# Yang Xiang <yang.xiang@pmi.com>
+# Author: Sylvain Gubian, PMP S.A.
+"""
+Unit tests for the dual annealing global optimizer
+"""
+from scipy.optimize import dual_annealing, Bounds
+
+from scipy.optimize._dual_annealing import EnergyState
+from scipy.optimize._dual_annealing import LocalSearchWrapper
+from scipy.optimize._dual_annealing import ObjectiveFunWrapper
+from scipy.optimize._dual_annealing import StrategyChain
+from scipy.optimize._dual_annealing import VisitingDistribution
+from scipy.optimize import rosen, rosen_der
+import pytest
+import numpy as np
+from numpy.testing import assert_equal, assert_allclose, assert_array_less
+from pytest import raises as assert_raises
+from scipy._lib._util import check_random_state
+
+import threading
+
+
+class TestDualAnnealing:
+
+    def setup_method(self):
+        # A function that returns always infinity for initialization tests
+        self.weirdfunc = lambda x: np.inf
+        # 2-D bounds for testing function
+        self.ld_bounds = [(-5.12, 5.12)] * 2
+        # 4-D bounds for testing function
+        self.hd_bounds = self.ld_bounds * 4
+        # Number of values to be generated for testing visit function
+        self.nbtestvalues = 5000
+        self.high_temperature = 5230
+        self.low_temperature = 0.1
+        self.qv = 2.62
+        self.seed = 1234
+        self.rng = check_random_state(self.seed)
+        self.nb_fun_call = threading.local()
+        self.ngev = threading.local()
+
+    def callback(self, x, f, context):
+        # For testing callback mechanism. Should stop for e <= 1 as
+        # the callback function returns True
+        if f <= 1.0:
+            return True
+
+    def func(self, x, args=()):
+        # Using Rastrigin function for performing tests
+        if args:
+            shift = args
+        else:
+            shift = 0
+        y = np.sum((x - shift) ** 2 - 10 * np.cos(2 * np.pi * (
+            x - shift))) + 10 * np.size(x) + shift
+        if not hasattr(self.nb_fun_call, 'c'):
+            self.nb_fun_call.c = 0
+        self.nb_fun_call.c += 1
+        return y
+
+    def rosen_der_wrapper(self, x, args=()):
+        if not hasattr(self.ngev, 'c'):
+            self.ngev.c = 0
+        self.ngev.c += 1
+        return rosen_der(x, *args)
+
+    # FIXME: there are some discontinuities in behaviour as a function of `qv`,
+    #        this needs investigating - see gh-12384
+    @pytest.mark.parametrize('qv', [1.1, 1.41, 2, 2.62, 2.9])
+    def test_visiting_stepping(self, qv):
+        lu = list(zip(*self.ld_bounds))
+        lower = np.array(lu[0])
+        upper = np.array(lu[1])
+        dim = lower.size
+        vd = VisitingDistribution(lower, upper, qv, self.rng)
+        values = np.zeros(dim)
+        x_step_low = vd.visiting(values, 0, self.high_temperature)
+        # Make sure that only the first component is changed
+        assert_equal(np.not_equal(x_step_low, 0), True)
+        values = np.zeros(dim)
+        x_step_high = vd.visiting(values, dim, self.high_temperature)
+        # Make sure that component other than at dim has changed
+        assert_equal(np.not_equal(x_step_high[0], 0), True)
+
+    @pytest.mark.parametrize('qv', [2.25, 2.62, 2.9])
+    def test_visiting_dist_high_temperature(self, qv):
+        lu = list(zip(*self.ld_bounds))
+        lower = np.array(lu[0])
+        upper = np.array(lu[1])
+        vd = VisitingDistribution(lower, upper, qv, self.rng)
+        # values = np.zeros(self.nbtestvalues)
+        # for i in np.arange(self.nbtestvalues):
+        #     values[i] = vd.visit_fn(self.high_temperature)
+        values = vd.visit_fn(self.high_temperature, self.nbtestvalues)
+
+        # Visiting distribution is a distorted version of Cauchy-Lorentz
+        # distribution, and as no 1st and higher moments (no mean defined,
+        # no variance defined).
+        # Check that big tails values are generated
+        assert_array_less(np.min(values), 1e-10)
+        assert_array_less(1e+10, np.max(values))
+
+    def test_reset(self):
+        owf = ObjectiveFunWrapper(self.weirdfunc)
+        lu = list(zip(*self.ld_bounds))
+        lower = np.array(lu[0])
+        upper = np.array(lu[1])
+        es = EnergyState(lower, upper)
+        assert_raises(ValueError, es.reset, owf, check_random_state(None))
+
+    def test_low_dim(self):
+        ret = dual_annealing(
+            self.func, self.ld_bounds, rng=self.seed)
+        assert_allclose(ret.fun, 0., atol=1e-12)
+        assert ret.success
+
+    @pytest.mark.fail_slow(10)
+    def test_high_dim(self):
+        ret = dual_annealing(self.func, self.hd_bounds, rng=self.seed)
+        assert_allclose(ret.fun, 0., atol=1e-12)
+        assert ret.success
+
+    def test_low_dim_no_ls(self):
+        ret = dual_annealing(self.func, self.ld_bounds,
+                             no_local_search=True, seed=self.seed)
+        assert_allclose(ret.fun, 0., atol=1e-4)
+
+    @pytest.mark.fail_slow(10)
+    def test_high_dim_no_ls(self):
+        ret = dual_annealing(self.func, self.hd_bounds,
+                             no_local_search=True, rng=self.seed)
+        assert_allclose(ret.fun, 0., atol=1.2e-4)
+
+    def test_nb_fun_call(self):
+        self.nb_fun_call.c = 0
+        ret = dual_annealing(self.func, self.ld_bounds, rng=self.seed)
+        assert_equal(self.nb_fun_call.c, ret.nfev)
+
+    def test_nb_fun_call_no_ls(self):
+        self.nb_fun_call.c = 0
+        ret = dual_annealing(self.func, self.ld_bounds,
+                             no_local_search=True, rng=self.seed)
+        assert_equal(self.nb_fun_call.c, ret.nfev)
+
+    def test_max_reinit(self):
+        assert_raises(ValueError, dual_annealing, self.weirdfunc,
+                      self.ld_bounds)
+
+    @pytest.mark.fail_slow(10)
+    def test_reproduce(self):
+        res1 = dual_annealing(self.func, self.ld_bounds, rng=self.seed)
+        res2 = dual_annealing(self.func, self.ld_bounds, rng=self.seed)
+        res3 = dual_annealing(self.func, self.ld_bounds, rng=self.seed)
+        # If we have reproducible results, x components found has to
+        # be exactly the same, which is not the case with no seeding
+        assert_equal(res1.x, res2.x)
+        assert_equal(res1.x, res3.x)
+
+    def test_rand_gen(self):
+        # check that np.random.Generator can be used (numpy >= 1.17)
+        # obtain a np.random.Generator object
+        rng = np.random.default_rng(1)
+
+        res1 = dual_annealing(self.func, self.ld_bounds, rng=rng)
+        # seed again
+        rng = np.random.default_rng(1)
+        res2 = dual_annealing(self.func, self.ld_bounds, rng=rng)
+        # If we have reproducible results, x components found has to
+        # be exactly the same, which is not the case with no seeding
+        assert_equal(res1.x, res2.x)
+
+    def test_bounds_integrity(self):
+        wrong_bounds = [(-5.12, 5.12), (1, 0), (5.12, 5.12)]
+        assert_raises(ValueError, dual_annealing, self.func,
+                      wrong_bounds)
+
+    def test_bound_validity(self):
+        invalid_bounds = [(-5, 5), (-np.inf, 0), (-5, 5)]
+        assert_raises(ValueError, dual_annealing, self.func,
+                      invalid_bounds)
+        invalid_bounds = [(-5, 5), (0, np.inf), (-5, 5)]
+        assert_raises(ValueError, dual_annealing, self.func,
+                      invalid_bounds)
+        invalid_bounds = [(-5, 5), (0, np.nan), (-5, 5)]
+        assert_raises(ValueError, dual_annealing, self.func,
+                      invalid_bounds)
+
+    @pytest.mark.thread_unsafe
+    def test_deprecated_local_search_options_bounds(self):
+        def func(x):
+            return np.sum((x - 5) * (x - 1))
+        bounds = list(zip([-6, -5], [6, 5]))
+        # Test bounds can be passed (see gh-10831)
+
+        with pytest.warns(RuntimeWarning, match=r"Method CG cannot handle "):
+            dual_annealing(
+                func,
+                bounds=bounds,
+                minimizer_kwargs={"method": "CG", "bounds": bounds})
+
+    @pytest.mark.thread_unsafe
+    def test_minimizer_kwargs_bounds(self):
+        def func(x):
+            return np.sum((x - 5) * (x - 1))
+        bounds = list(zip([-6, -5], [6, 5]))
+        # Test bounds can be passed (see gh-10831)
+        dual_annealing(
+            func,
+            bounds=bounds,
+            minimizer_kwargs={"method": "SLSQP", "bounds": bounds})
+
+        with pytest.warns(RuntimeWarning, match=r"Method CG cannot handle "):
+            dual_annealing(
+                func,
+                bounds=bounds,
+                minimizer_kwargs={"method": "CG", "bounds": bounds})
+
+    def test_max_fun_ls(self):
+        ret = dual_annealing(self.func, self.ld_bounds, maxfun=100,
+                             rng=self.seed)
+
+        ls_max_iter = min(max(
+            len(self.ld_bounds) * LocalSearchWrapper.LS_MAXITER_RATIO,
+            LocalSearchWrapper.LS_MAXITER_MIN),
+            LocalSearchWrapper.LS_MAXITER_MAX)
+        assert ret.nfev <= 100 + ls_max_iter
+        assert not ret.success
+
+    def test_max_fun_no_ls(self):
+        ret = dual_annealing(self.func, self.ld_bounds,
+                             no_local_search=True, maxfun=500, rng=self.seed)
+        assert ret.nfev <= 500
+        assert not ret.success
+
+    def test_maxiter(self):
+        ret = dual_annealing(self.func, self.ld_bounds, maxiter=700,
+                             rng=self.seed)
+        assert ret.nit <= 700
+
+    # Testing that args are passed correctly for dual_annealing
+    def test_fun_args_ls(self):
+        ret = dual_annealing(self.func, self.ld_bounds,
+                             args=((3.14159,)), rng=self.seed)
+        assert_allclose(ret.fun, 3.14159, atol=1e-6)
+
+    # Testing that args are passed correctly for pure simulated annealing
+    def test_fun_args_no_ls(self):
+        ret = dual_annealing(self.func, self.ld_bounds,
+                             args=((3.14159, )), no_local_search=True,
+                             rng=self.seed)
+        assert_allclose(ret.fun, 3.14159, atol=1e-4)
+
+    def test_callback_stop(self):
+        # Testing that callback make the algorithm stop for
+        # fun value <= 1.0 (see callback method)
+        ret = dual_annealing(self.func, self.ld_bounds,
+                             callback=self.callback, rng=self.seed)
+        assert ret.fun <= 1.0
+        assert 'stop early' in ret.message[0]
+        assert not ret.success
+
+    @pytest.mark.parametrize('method, atol', [
+        ('Nelder-Mead', 2e-5),
+        ('COBYLA', 1e-5),
+        ('COBYQA', 1e-8),
+        ('Powell', 1e-8),
+        ('CG', 1e-8),
+        ('BFGS', 1e-8),
+        ('TNC', 1e-8),
+        ('SLSQP', 2e-7),
+    ])
+    def test_multi_ls_minimizer(self, method, atol):
+        ret = dual_annealing(self.func, self.ld_bounds,
+                             minimizer_kwargs=dict(method=method),
+                             rng=self.seed)
+        assert_allclose(ret.fun, 0., atol=atol)
+
+    def test_wrong_restart_temp(self):
+        assert_raises(ValueError, dual_annealing, self.func,
+                      self.ld_bounds, restart_temp_ratio=1)
+        assert_raises(ValueError, dual_annealing, self.func,
+                      self.ld_bounds, restart_temp_ratio=0)
+
+    def test_gradient_gnev(self):
+        minimizer_opts = {
+            'jac': self.rosen_der_wrapper,
+        }
+        ret = dual_annealing(rosen, self.ld_bounds,
+                             minimizer_kwargs=minimizer_opts,
+                             rng=self.seed)
+        assert ret.njev == self.ngev.c
+
+    @pytest.mark.fail_slow(10)
+    def test_from_docstring(self):
+        def func(x):
+            return np.sum(x * x - 10 * np.cos(2 * np.pi * x)) + 10 * np.size(x)
+        lw = [-5.12] * 10
+        up = [5.12] * 10
+        ret = dual_annealing(func, bounds=list(zip(lw, up)), rng=1234)
+        assert_allclose(ret.x,
+                        [-4.26437714e-09, -3.91699361e-09, -1.86149218e-09,
+                         -3.97165720e-09, -6.29151648e-09, -6.53145322e-09,
+                         -3.93616815e-09, -6.55623025e-09, -6.05775280e-09,
+                         -5.00668935e-09], atol=4e-8)
+        assert_allclose(ret.fun, 0.000000, atol=5e-13)
+
+    @pytest.mark.parametrize('new_e, temp_step, accepted, accept_rate', [
+        (0, 100, 1000, 1.0097587941791923),
+        (0, 2, 1000, 1.2599210498948732),
+        (10, 100, 878, 0.8786035869128718),
+        (10, 60, 695, 0.6812920690579612),
+        (2, 100, 990, 0.9897404249173424),
+    ])
+    def test_accept_reject_probabilistic(
+            self, new_e, temp_step, accepted, accept_rate):
+        # Test accepts unconditionally with e < current_energy and
+        # probabilistically with e > current_energy
+
+        rs = check_random_state(123)
+
+        count_accepted = 0
+        iterations = 1000
+
+        accept_param = -5
+        current_energy = 1
+        for _ in range(iterations):
+            energy_state = EnergyState(lower=None, upper=None)
+            # Set energy state with current_energy, any location.
+            energy_state.update_current(current_energy, [0])
+
+            chain = StrategyChain(
+                accept_param, None, None, None, rs, energy_state)
+            # Normally this is set in run()
+            chain.temperature_step = temp_step
+
+            # Check if update is accepted.
+            chain.accept_reject(j=1, e=new_e, x_visit=[2])
+            if energy_state.current_energy == new_e:
+                count_accepted += 1
+
+        assert count_accepted == accepted
+
+        # Check accept rate
+        pqv = 1 - (1 - accept_param) * (new_e - current_energy) / temp_step
+        rate = 0 if pqv <= 0 else np.exp(np.log(pqv) / (1 - accept_param))
+
+        assert_allclose(rate, accept_rate)
+
+    @pytest.mark.fail_slow(10)
+    def test_bounds_class(self):
+        # test that result does not depend on the bounds type
+        def func(x):
+            f = np.sum(x * x - 10 * np.cos(2 * np.pi * x)) + 10 * np.size(x)
+            return f
+        lw = [-5.12] * 5
+        up = [5.12] * 5
+
+        # Unbounded global minimum is all zeros. Most bounds below will force
+        # a DV away from unbounded minimum and be active at solution.
+        up[0] = -2.0
+        up[1] = -1.0
+        lw[3] = 1.0
+        lw[4] = 2.0
+
+        # run optimizations
+        bounds = Bounds(lw, up)
+        ret_bounds_class = dual_annealing(func, bounds=bounds, rng=1234)
+
+        bounds_old = list(zip(lw, up))
+        ret_bounds_list = dual_annealing(func, bounds=bounds_old, rng=1234)
+
+        # test that found minima, function evaluations and iterations match
+        assert_allclose(ret_bounds_class.x, ret_bounds_list.x, atol=1e-8)
+        assert_allclose(ret_bounds_class.x, np.arange(-2, 3), atol=1e-7)
+        assert_allclose(ret_bounds_list.fun, ret_bounds_class.fun, atol=1e-9)
+        assert ret_bounds_list.nfev == ret_bounds_class.nfev
+
+    @pytest.mark.fail_slow(10)
+    def test_callable_jac_hess_with_args_gh11052(self):
+        # dual_annealing used to fail when `jac` was callable and `args` were
+        # used; check that this is resolved. Example is from gh-11052.
+
+        # extended to hess as part of closing gh20614
+        rng = np.random.default_rng(94253637693657847462)
+        def f(x, power):
+            return np.sum(np.exp(x ** power))
+
+        def jac(x, power):
+            return np.exp(x ** power) * power * x ** (power - 1)
+
+        def hess(x, power):
+            # calculated using WolframAlpha as d^2/dx^2 e^(x^p)
+            return np.diag(
+                power * np.exp(x ** power) * x ** (power - 2) *
+                (power * x ** power + power - 1)
+            )
+
+        def hessp(x, p, power):
+            return hess(x, power) @ p
+
+        res1 = dual_annealing(f, args=(2, ), bounds=[[0, 1], [0, 1]], rng=rng,
+                              minimizer_kwargs=dict(method='L-BFGS-B'))
+        res2 = dual_annealing(f, args=(2, ), bounds=[[0, 1], [0, 1]], rng=rng,
+                              minimizer_kwargs=dict(method='L-BFGS-B',
+                                                    jac=jac))
+        res3 = dual_annealing(f, args=(2, ), bounds=[[0, 1], [0, 1]], rng=rng,
+                              minimizer_kwargs=dict(method='newton-cg',
+                                                    jac=jac, hess=hess))
+        res4 = dual_annealing(f, args=(2, ), bounds=[[0, 1], [0, 1]], rng=rng,
+                              minimizer_kwargs=dict(method='newton-cg',
+                                                    jac=jac, hessp=hessp))
+        assert_allclose(res1.fun, res2.fun, rtol=1e-6)
+        assert_allclose(res3.fun, res2.fun, rtol=1e-6)
+        assert_allclose(res4.fun, res2.fun, rtol=1e-6)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test__linprog_clean_inputs.py

@@ -0,0 +1,312 @@
+"""
+Unit test for Linear Programming via Simplex Algorithm.
+"""
+from copy import deepcopy
+from datetime import date
+
+import numpy as np
+from numpy.testing import assert_, assert_allclose, assert_equal
+from numpy.exceptions import VisibleDeprecationWarning
+from pytest import raises as assert_raises
+
+from scipy.optimize._linprog_util import _clean_inputs, _LPProblem
+
+
+def test_aliasing():
+    """
+    Test for ensuring that no objects referred to by `lp` attributes,
+    `c`, `A_ub`, `b_ub`, `A_eq`, `b_eq`, `bounds`, have been modified
+    by `_clean_inputs` as a side effect.
+    """
+    lp = _LPProblem(
+        c=1,
+        A_ub=[[1]],
+        b_ub=[1],
+        A_eq=[[1]],
+        b_eq=[1],
+        bounds=(-np.inf, np.inf)
+    )
+    lp_copy = deepcopy(lp)
+
+    _clean_inputs(lp)
+
+    assert_(lp.c == lp_copy.c, "c modified by _clean_inputs")
+    assert_(lp.A_ub == lp_copy.A_ub, "A_ub modified by _clean_inputs")
+    assert_(lp.b_ub == lp_copy.b_ub, "b_ub modified by _clean_inputs")
+    assert_(lp.A_eq == lp_copy.A_eq, "A_eq modified by _clean_inputs")
+    assert_(lp.b_eq == lp_copy.b_eq, "b_eq modified by _clean_inputs")
+    assert_(lp.bounds == lp_copy.bounds, "bounds modified by _clean_inputs")
+
+
+def test_aliasing2():
+    """
+    Similar purpose as `test_aliasing` above.
+    """
+    lp = _LPProblem(
+        c=np.array([1, 1]),
+        A_ub=np.array([[1, 1], [2, 2]]),
+        b_ub=np.array([[1], [1]]),
+        A_eq=np.array([[1, 1]]),
+        b_eq=np.array([1]),
+        bounds=[(-np.inf, np.inf), (None, 1)]
+    )
+    lp_copy = deepcopy(lp)
+
+    _clean_inputs(lp)
+
+    assert_allclose(lp.c, lp_copy.c, err_msg="c modified by _clean_inputs")
+    assert_allclose(lp.A_ub, lp_copy.A_ub, err_msg="A_ub modified by _clean_inputs")
+    assert_allclose(lp.b_ub, lp_copy.b_ub, err_msg="b_ub modified by _clean_inputs")
+    assert_allclose(lp.A_eq, lp_copy.A_eq, err_msg="A_eq modified by _clean_inputs")
+    assert_allclose(lp.b_eq, lp_copy.b_eq, err_msg="b_eq modified by _clean_inputs")
+    assert_(lp.bounds == lp_copy.bounds, "bounds modified by _clean_inputs")
+
+
+def test_missing_inputs():
+    c = [1, 2]
+    A_ub = np.array([[1, 1], [2, 2]])
+    b_ub = np.array([1, 1])
+    A_eq = np.array([[1, 1], [2, 2]])
+    b_eq = np.array([1, 1])
+
+    assert_raises(TypeError, _clean_inputs)
+    assert_raises(TypeError, _clean_inputs, _LPProblem(c=None))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_ub=A_ub))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_ub=A_ub, b_ub=None))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, b_ub=b_ub))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_ub=None, b_ub=b_ub))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_eq=A_eq))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_eq=A_eq, b_eq=None))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, b_eq=b_eq))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_eq=None, b_eq=b_eq))
+
+
+def test_too_many_dimensions():
+    cb = [1, 2, 3, 4]
+    A = np.random.rand(4, 4)
+    bad2D = [[1, 2], [3, 4]]
+    bad3D = np.random.rand(4, 4, 4)
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=bad2D, A_ub=A, b_ub=cb))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=cb, A_ub=bad3D, b_ub=cb))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=cb, A_ub=A, b_ub=bad2D))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=cb, A_eq=bad3D, b_eq=cb))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=cb, A_eq=A, b_eq=bad2D))
+
+
+def test_too_few_dimensions():
+    bad = np.random.rand(4, 4).ravel()
+    cb = np.random.rand(4)
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=cb, A_ub=bad, b_ub=cb))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=cb, A_eq=bad, b_eq=cb))
+
+
+def test_inconsistent_dimensions():
+    m = 2
+    n = 4
+    c = [1, 2, 3, 4]
+
+    Agood = np.random.rand(m, n)
+    Abad = np.random.rand(m, n + 1)
+    bgood = np.random.rand(m)
+    bbad = np.random.rand(m + 1)
+    boundsbad = [(0, 1)] * (n + 1)
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_ub=Abad, b_ub=bgood))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_ub=Agood, b_ub=bbad))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_eq=Abad, b_eq=bgood))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, A_eq=Agood, b_eq=bbad))
+    assert_raises(ValueError, _clean_inputs, _LPProblem(c=c, bounds=boundsbad))
+    with np.testing.suppress_warnings() as sup:
+        sup.filter(VisibleDeprecationWarning, "Creating an ndarray from ragged")
+        assert_raises(ValueError, _clean_inputs,
+                      _LPProblem(c=c, bounds=[[1, 2], [2, 3], [3, 4], [4, 5, 6]]))
+
+
+def test_type_errors():
+    lp = _LPProblem(
+        c=[1, 2],
+        A_ub=np.array([[1, 1], [2, 2]]),
+        b_ub=np.array([1, 1]),
+        A_eq=np.array([[1, 1], [2, 2]]),
+        b_eq=np.array([1, 1]),
+        bounds=[(0, 1)]
+    )
+    bad = "hello"
+
+    assert_raises(TypeError, _clean_inputs, lp._replace(c=bad))
+    assert_raises(TypeError, _clean_inputs, lp._replace(A_ub=bad))
+    assert_raises(TypeError, _clean_inputs, lp._replace(b_ub=bad))
+    assert_raises(TypeError, _clean_inputs, lp._replace(A_eq=bad))
+    assert_raises(TypeError, _clean_inputs, lp._replace(b_eq=bad))
+
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds=bad))
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds="hi"))
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds=["hi"]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds=[("hi")]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds=[(1, "")]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds=[(1, 2), (1, "")]))
+    assert_raises(TypeError, _clean_inputs,
+                  lp._replace(bounds=[(1, date(2020, 2, 29))]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds=[[[1, 2]]]))
+
+
+def test_non_finite_errors():
+    lp = _LPProblem(
+        c=[1, 2],
+        A_ub=np.array([[1, 1], [2, 2]]),
+        b_ub=np.array([1, 1]),
+        A_eq=np.array([[1, 1], [2, 2]]),
+        b_eq=np.array([1, 1]),
+        bounds=[(0, 1)]
+    )
+    assert_raises(ValueError, _clean_inputs, lp._replace(c=[0, None]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(c=[np.inf, 0]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(c=[0, -np.inf]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(c=[np.nan, 0]))
+
+    assert_raises(ValueError, _clean_inputs, lp._replace(A_ub=[[1, 2], [None, 1]]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(b_ub=[np.inf, 1]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(A_eq=[[1, 2], [1, -np.inf]]))
+    assert_raises(ValueError, _clean_inputs, lp._replace(b_eq=[1, np.nan]))
+
+
+def test__clean_inputs1():
+    lp = _LPProblem(
+        c=[1, 2],
+        A_ub=[[1, 1], [2, 2]],
+        b_ub=[1, 1],
+        A_eq=[[1, 1], [2, 2]],
+        b_eq=[1, 1],
+        bounds=None
+    )
+
+    lp_cleaned = _clean_inputs(lp)
+
+    assert_allclose(lp_cleaned.c, np.array(lp.c))
+    assert_allclose(lp_cleaned.A_ub, np.array(lp.A_ub))
+    assert_allclose(lp_cleaned.b_ub, np.array(lp.b_ub))
+    assert_allclose(lp_cleaned.A_eq, np.array(lp.A_eq))
+    assert_allclose(lp_cleaned.b_eq, np.array(lp.b_eq))
+    assert_equal(lp_cleaned.bounds, [(0, np.inf)] * 2)
+
+    assert_(lp_cleaned.c.shape == (2,), "")
+    assert_(lp_cleaned.A_ub.shape == (2, 2), "")
+    assert_(lp_cleaned.b_ub.shape == (2,), "")
+    assert_(lp_cleaned.A_eq.shape == (2, 2), "")
+    assert_(lp_cleaned.b_eq.shape == (2,), "")
+
+
+def test__clean_inputs2():
+    lp = _LPProblem(
+        c=1,
+        A_ub=[[1]],
+        b_ub=1,
+        A_eq=[[1]],
+        b_eq=1,
+        bounds=(0, 1)
+    )
+
+    lp_cleaned = _clean_inputs(lp)
+
+    assert_allclose(lp_cleaned.c, np.array(lp.c))
+    assert_allclose(lp_cleaned.A_ub, np.array(lp.A_ub))
+    assert_allclose(lp_cleaned.b_ub, np.array(lp.b_ub))
+    assert_allclose(lp_cleaned.A_eq, np.array(lp.A_eq))
+    assert_allclose(lp_cleaned.b_eq, np.array(lp.b_eq))
+    assert_equal(lp_cleaned.bounds, [(0, 1)])
+
+    assert_(lp_cleaned.c.shape == (1,), "")
+    assert_(lp_cleaned.A_ub.shape == (1, 1), "")
+    assert_(lp_cleaned.b_ub.shape == (1,), "")
+    assert_(lp_cleaned.A_eq.shape == (1, 1), "")
+    assert_(lp_cleaned.b_eq.shape == (1,), "")
+
+
+def test__clean_inputs3():
+    lp = _LPProblem(
+        c=[[1, 2]],
+        A_ub=np.random.rand(2, 2),
+        b_ub=[[1], [2]],
+        A_eq=np.random.rand(2, 2),
+        b_eq=[[1], [2]],
+        bounds=[(0, 1)]
+    )
+
+    lp_cleaned = _clean_inputs(lp)
+
+    assert_allclose(lp_cleaned.c, np.array([1, 2]))
+    assert_allclose(lp_cleaned.b_ub, np.array([1, 2]))
+    assert_allclose(lp_cleaned.b_eq, np.array([1, 2]))
+    assert_equal(lp_cleaned.bounds, [(0, 1)] * 2)
+
+    assert_(lp_cleaned.c.shape == (2,), "")
+    assert_(lp_cleaned.b_ub.shape == (2,), "")
+    assert_(lp_cleaned.b_eq.shape == (2,), "")
+
+
+def test_bad_bounds():
+    lp = _LPProblem(c=[1, 2])
+
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds=(1, 2, 2)))
+    assert_raises(ValueError, _clean_inputs, lp._replace(bounds=[(1, 2, 2)]))
+    with np.testing.suppress_warnings() as sup:
+        sup.filter(VisibleDeprecationWarning, "Creating an ndarray from ragged")
+        assert_raises(ValueError, _clean_inputs,
+                      lp._replace(bounds=[(1, 2), (1, 2, 2)]))
+    assert_raises(ValueError, _clean_inputs,
+                  lp._replace(bounds=[(1, 2), (1, 2), (1, 2)]))
+
+    lp = _LPProblem(c=[1, 2, 3, 4])
+
+    assert_raises(ValueError, _clean_inputs,
+                  lp._replace(bounds=[(1, 2, 3, 4), (1, 2, 3, 4)]))
+
+
+def test_good_bounds():
+    lp = _LPProblem(c=[1, 2])
+
+    lp_cleaned = _clean_inputs(lp)  # lp.bounds is None by default
+    assert_equal(lp_cleaned.bounds, [(0, np.inf)] * 2)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[]))
+    assert_equal(lp_cleaned.bounds, [(0, np.inf)] * 2)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[[]]))
+    assert_equal(lp_cleaned.bounds, [(0, np.inf)] * 2)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=(1, 2)))
+    assert_equal(lp_cleaned.bounds, [(1, 2)] * 2)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[(1, 2)]))
+    assert_equal(lp_cleaned.bounds, [(1, 2)] * 2)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[(1, None)]))
+    assert_equal(lp_cleaned.bounds, [(1, np.inf)] * 2)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[(None, 1)]))
+    assert_equal(lp_cleaned.bounds, [(-np.inf, 1)] * 2)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[(None, None), (-np.inf, None)]))
+    assert_equal(lp_cleaned.bounds, [(-np.inf, np.inf)] * 2)
+
+    lp = _LPProblem(c=[1, 2, 3, 4])
+
+    lp_cleaned = _clean_inputs(lp)  # lp.bounds is None by default
+    assert_equal(lp_cleaned.bounds, [(0, np.inf)] * 4)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=(1, 2)))
+    assert_equal(lp_cleaned.bounds, [(1, 2)] * 4)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[(1, 2)]))
+    assert_equal(lp_cleaned.bounds, [(1, 2)] * 4)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[(1, None)]))
+    assert_equal(lp_cleaned.bounds, [(1, np.inf)] * 4)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[(None, 1)]))
+    assert_equal(lp_cleaned.bounds, [(-np.inf, 1)] * 4)
+
+    lp_cleaned = _clean_inputs(lp._replace(bounds=[(None, None),
+                                                   (-np.inf, None),
+                                                   (None, np.inf),
+                                                   (-np.inf, np.inf)]))
+    assert_equal(lp_cleaned.bounds, [(-np.inf, np.inf)] * 4)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test__numdiff.py

@@ -0,0 +1,885 @@
+import math
+from itertools import product
+
+import numpy as np
+from numpy.testing import assert_allclose, assert_equal, assert_
+import pytest
+from pytest import raises as assert_raises
+
+from scipy._lib._util import MapWrapper, _ScalarFunctionWrapper
+from scipy.sparse import csr_array, csc_array, lil_array
+
+from scipy.optimize._numdiff import (
+    _adjust_scheme_to_bounds, approx_derivative, check_derivative,
+    group_columns, _eps_for_method, _compute_absolute_step)
+from scipy.optimize import rosen
+
+
+def test_group_columns():
+    structure = [
+        [1, 1, 0, 0, 0, 0],
+        [1, 1, 1, 0, 0, 0],
+        [0, 1, 1, 1, 0, 0],
+        [0, 0, 1, 1, 1, 0],
+        [0, 0, 0, 1, 1, 1],
+        [0, 0, 0, 0, 1, 1],
+        [0, 0, 0, 0, 0, 0]
+    ]
+    for transform in [np.asarray, csr_array, csc_array, lil_array]:
+        A = transform(structure)
+        order = np.arange(6)
+        groups_true = np.array([0, 1, 2, 0, 1, 2])
+        groups = group_columns(A, order)
+        assert_equal(groups, groups_true)
+
+        order = [1, 2, 4, 3, 5, 0]
+        groups_true = np.array([2, 0, 1, 2, 0, 1])
+        groups = group_columns(A, order)
+        assert_equal(groups, groups_true)
+
+    # Test repeatability.
+    groups_1 = group_columns(A)
+    groups_2 = group_columns(A)
+    assert_equal(groups_1, groups_2)
+
+
+def test_correct_fp_eps():
+    # check that relative step size is correct for FP size
+    EPS = np.finfo(np.float64).eps
+    relative_step = {"2-point": EPS**0.5,
+                    "3-point": EPS**(1/3),
+                     "cs": EPS**0.5}
+    for method in ['2-point', '3-point', 'cs']:
+        assert_allclose(
+            _eps_for_method(np.float64, np.float64, method),
+            relative_step[method])
+        assert_allclose(
+            _eps_for_method(np.complex128, np.complex128, method),
+            relative_step[method]
+        )
+
+    # check another FP size
+    EPS = np.finfo(np.float32).eps
+    relative_step = {"2-point": EPS**0.5,
+                    "3-point": EPS**(1/3),
+                     "cs": EPS**0.5}
+
+    for method in ['2-point', '3-point', 'cs']:
+        assert_allclose(
+            _eps_for_method(np.float64, np.float32, method),
+            relative_step[method]
+        )
+        assert_allclose(
+            _eps_for_method(np.float32, np.float64, method),
+            relative_step[method]
+        )
+        assert_allclose(
+            _eps_for_method(np.float32, np.float32, method),
+            relative_step[method]
+        )
+
+
+class TestAdjustSchemeToBounds:
+    def test_no_bounds(self):
+        x0 = np.zeros(3)
+        h = np.full(3, 1e-2)
+        inf_lower = np.empty_like(x0)
+        inf_upper = np.empty_like(x0)
+        inf_lower.fill(-np.inf)
+        inf_upper.fill(np.inf)
+
+        h_adjusted, one_sided = _adjust_scheme_to_bounds(
+            x0, h, 1, '1-sided', inf_lower, inf_upper)
+        assert_allclose(h_adjusted, h)
+        assert_(np.all(one_sided))
+
+        h_adjusted, one_sided = _adjust_scheme_to_bounds(
+            x0, h, 2, '1-sided', inf_lower, inf_upper)
+        assert_allclose(h_adjusted, h)
+        assert_(np.all(one_sided))
+
+        h_adjusted, one_sided = _adjust_scheme_to_bounds(
+            x0, h, 1, '2-sided', inf_lower, inf_upper)
+        assert_allclose(h_adjusted, h)
+        assert_(np.all(~one_sided))
+
+        h_adjusted, one_sided = _adjust_scheme_to_bounds(
+            x0, h, 2, '2-sided', inf_lower, inf_upper)
+        assert_allclose(h_adjusted, h)
+        assert_(np.all(~one_sided))
+
+    def test_with_bound(self):
+        x0 = np.array([0.0, 0.85, -0.85])
+        lb = -np.ones(3)
+        ub = np.ones(3)
+        h = np.array([1, 1, -1]) * 1e-1
+
+        h_adjusted, _ = _adjust_scheme_to_bounds(x0, h, 1, '1-sided', lb, ub)
+        assert_allclose(h_adjusted, h)
+
+        h_adjusted, _ = _adjust_scheme_to_bounds(x0, h, 2, '1-sided', lb, ub)
+        assert_allclose(h_adjusted, np.array([1, -1, 1]) * 1e-1)
+
+        h_adjusted, one_sided = _adjust_scheme_to_bounds(
+            x0, h, 1, '2-sided', lb, ub)
+        assert_allclose(h_adjusted, np.abs(h))
+        assert_(np.all(~one_sided))
+
+        h_adjusted, one_sided = _adjust_scheme_to_bounds(
+            x0, h, 2, '2-sided', lb, ub)
+        assert_allclose(h_adjusted, np.array([1, -1, 1]) * 1e-1)
+        assert_equal(one_sided, np.array([False, True, True]))
+
+    def test_tight_bounds(self):
+        lb = np.array([-0.03, -0.03])
+        ub = np.array([0.05, 0.05])
+        x0 = np.array([0.0, 0.03])
+        h = np.array([-0.1, -0.1])
+
+        h_adjusted, _ = _adjust_scheme_to_bounds(x0, h, 1, '1-sided', lb, ub)
+        assert_allclose(h_adjusted, np.array([0.05, -0.06]))
+
+        h_adjusted, _ = _adjust_scheme_to_bounds(x0, h, 2, '1-sided', lb, ub)
+        assert_allclose(h_adjusted, np.array([0.025, -0.03]))
+
+        h_adjusted, one_sided = _adjust_scheme_to_bounds(
+            x0, h, 1, '2-sided', lb, ub)
+        assert_allclose(h_adjusted, np.array([0.03, -0.03]))
+        assert_equal(one_sided, np.array([False, True]))
+
+        h_adjusted, one_sided = _adjust_scheme_to_bounds(
+            x0, h, 2, '2-sided', lb, ub)
+        assert_allclose(h_adjusted, np.array([0.015, -0.015]))
+        assert_equal(one_sided, np.array([False, True]))
+
+
+class TestApproxDerivativesDense:
+    def fun_scalar_scalar(self, x):
+        return np.sinh(x)
+
+    def jac_scalar_scalar(self, x):
+        return np.cosh(x)
+
+    def fun_scalar_vector(self, x):
+        return np.array([x[0]**2, np.tan(x[0]), np.exp(x[0])])
+
+    def jac_scalar_vector(self, x):
+        return np.array(
+            [2 * x[0], np.cos(x[0]) ** -2, np.exp(x[0])]).reshape(-1, 1)
+
+    def fun_vector_scalar(self, x):
+        return np.sin(x[0] * x[1]) * np.log(x[0])
+
+    def wrong_dimensions_fun(self, x):
+        return np.array([x**2, np.tan(x), np.exp(x)])
+
+    def jac_vector_scalar(self, x):
+        return np.array([
+            x[1] * np.cos(x[0] * x[1]) * np.log(x[0]) +
+            np.sin(x[0] * x[1]) / x[0],
+            x[0] * np.cos(x[0] * x[1]) * np.log(x[0])
+        ])
+
+    def fun_vector_vector(self, x):
+        return np.array([
+            x[0] * np.sin(x[1]),
+            x[1] * np.cos(x[0]),
+            x[0] ** 3 * x[1] ** -0.5
+        ])
+
+    def fun_vector_vector_with_arg(self, x, arg):
+        """Used to test passing custom arguments with check_derivative()"""
+        assert arg == 42
+        return np.array([
+            x[0] * np.sin(x[1]),
+            x[1] * np.cos(x[0]),
+            x[0] ** 3 * x[1] ** -0.5
+        ])
+
+    def jac_vector_vector(self, x):
+        return np.array([
+            [np.sin(x[1]), x[0] * np.cos(x[1])],
+            [-x[1] * np.sin(x[0]), np.cos(x[0])],
+            [3 * x[0] ** 2 * x[1] ** -0.5, -0.5 * x[0] ** 3 * x[1] ** -1.5]
+        ])
+
+    def jac_vector_vector_with_arg(self, x, arg):
+        """Used to test passing custom arguments with check_derivative()"""
+        assert arg == 42
+        return np.array([
+            [np.sin(x[1]), x[0] * np.cos(x[1])],
+            [-x[1] * np.sin(x[0]), np.cos(x[0])],
+            [3 * x[0] ** 2 * x[1] ** -0.5, -0.5 * x[0] ** 3 * x[1] ** -1.5]
+        ])
+
+    def fun_parametrized(self, x, c0, c1=1.0):
+        return np.array([np.exp(c0 * x[0]), np.exp(c1 * x[1])])
+
+    def jac_parametrized(self, x, c0, c1=0.1):
+        return np.array([
+            [c0 * np.exp(c0 * x[0]), 0],
+            [0, c1 * np.exp(c1 * x[1])]
+        ])
+
+    def fun_with_nan(self, x):
+        return x if np.abs(x) <= 1e-8 else np.nan
+
+    def jac_with_nan(self, x):
+        return 1.0 if np.abs(x) <= 1e-8 else np.nan
+
+    def fun_zero_jacobian(self, x):
+        return np.array([x[0] * x[1], np.cos(x[0] * x[1])])
+
+    def jac_zero_jacobian(self, x):
+        return np.array([
+            [x[1], x[0]],
+            [-x[1] * np.sin(x[0] * x[1]), -x[0] * np.sin(x[0] * x[1])]
+        ])
+
+    def jac_non_numpy(self, x):
+        # x can be a scalar or an array [val].
+        # Cast to true scalar before handing over to math.exp
+        xp = np.asarray(x).item()
+        return math.exp(xp)
+
+    def test_scalar_scalar(self):
+        x0 = 1.0
+        jac_diff_2 = approx_derivative(self.fun_scalar_scalar, x0,
+                                       method='2-point')
+        jac_diff_3 = approx_derivative(self.fun_scalar_scalar, x0)
+        jac_diff_4 = approx_derivative(self.fun_scalar_scalar, x0,
+                                       method='cs')
+        jac_true = self.jac_scalar_scalar(x0)
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-9)
+        assert_allclose(jac_diff_4, jac_true, rtol=1e-12)
+
+    def test_scalar_scalar_abs_step(self):
+        # can approx_derivative use abs_step?
+        x0 = 1.0
+        jac_diff_2 = approx_derivative(self.fun_scalar_scalar, x0,
+                                       method='2-point', abs_step=1.49e-8)
+        jac_diff_3 = approx_derivative(self.fun_scalar_scalar, x0,
+                                       abs_step=1.49e-8)
+        jac_diff_4 = approx_derivative(self.fun_scalar_scalar, x0,
+                                       method='cs', abs_step=1.49e-8)
+        jac_true = self.jac_scalar_scalar(x0)
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-9)
+        assert_allclose(jac_diff_4, jac_true, rtol=1e-12)
+
+    def test_scalar_vector(self):
+        x0 = 0.5
+        with MapWrapper(2) as mapper:
+            jac_diff_2 = approx_derivative(self.fun_scalar_vector, x0,
+                                           method='2-point', workers=mapper)
+        jac_diff_3 = approx_derivative(self.fun_scalar_vector, x0, workers=map)
+        jac_diff_4 = approx_derivative(self.fun_scalar_vector, x0,
+                                       method='cs', workers=None)
+        jac_true = self.jac_scalar_vector(np.atleast_1d(x0))
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-9)
+        assert_allclose(jac_diff_4, jac_true, rtol=1e-12)
+
+    @pytest.mark.fail_slow(5.0)
+    def test_workers_evaluations_and_nfev(self):
+        # check that nfev consumed by approx_derivative is tracked properly
+        # and that parallel evaluation is same as series
+        x0 = [0.5, 1.5, 2.0]
+        with MapWrapper(2) as mapper:
+            md2, mdct2 = approx_derivative(rosen, x0,
+                                           method='2-point', workers=mapper,
+                                           full_output=True)
+            md3, mdct3 = approx_derivative(rosen, x0,
+                                           workers=mapper, full_output=True)
+        # supply a number for workers. This is not normally recommended
+        # for upstream workers as setting up processes incurs a large overhead
+        md4, mdct4 = approx_derivative(rosen, x0,
+                                       method='cs', workers=2,
+                                       full_output=True)
+
+        sfr = _ScalarFunctionWrapper(rosen)
+        d2, dct2 = approx_derivative(sfr, x0, method='2-point', full_output=True)
+        assert_equal(dct2['nfev'], sfr.nfev)
+        sfr.nfev = 0
+        d3, dct3 = approx_derivative(sfr, x0, full_output=True)
+        assert_equal(dct3['nfev'], sfr.nfev)
+        sfr.nfev = 0
+        d4, dct4 = approx_derivative(sfr, x0, method='cs', full_output=True)
+        assert_equal(dct4['nfev'], sfr.nfev)
+
+        assert_equal(mdct2['nfev'], dct2['nfev'])
+        assert_equal(mdct3['nfev'], dct3['nfev'])
+        assert_equal(mdct4['nfev'], dct4['nfev'])
+        # also check that gradients are equivalent
+        assert_equal(md2, d2)
+        assert_equal(md3, d3)
+        assert_equal(md4, d4)
+
+    def test_vector_scalar(self):
+        x0 = np.array([100.0, -0.5])
+        jac_diff_2 = approx_derivative(self.fun_vector_scalar, x0,
+                                       method='2-point')
+        jac_diff_3 = approx_derivative(self.fun_vector_scalar, x0)
+        jac_diff_4 = approx_derivative(self.fun_vector_scalar, x0,
+                                       method='cs')
+        jac_true = self.jac_vector_scalar(x0)
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-7)
+        assert_allclose(jac_diff_4, jac_true, rtol=1e-12)
+
+    def test_vector_scalar_abs_step(self):
+        # can approx_derivative use abs_step?
+        x0 = np.array([100.0, -0.5])
+        jac_diff_2 = approx_derivative(self.fun_vector_scalar, x0,
+                                       method='2-point', abs_step=1.49e-8)
+        jac_diff_3 = approx_derivative(self.fun_vector_scalar, x0,
+                                       abs_step=1.49e-8, rel_step=np.inf)
+        jac_diff_4 = approx_derivative(self.fun_vector_scalar, x0,
+                                       method='cs', abs_step=1.49e-8)
+        jac_true = self.jac_vector_scalar(x0)
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=3e-9)
+        assert_allclose(jac_diff_4, jac_true, rtol=1e-12)
+
+    def test_vector_vector(self):
+        x0 = np.array([-100.0, 0.2])
+        jac_diff_2 = approx_derivative(self.fun_vector_vector, x0,
+                                       method='2-point')
+        jac_diff_3 = approx_derivative(self.fun_vector_vector, x0)
+        with MapWrapper(2) as mapper:
+            jac_diff_4 = approx_derivative(self.fun_vector_vector, x0,
+                                           method='cs', workers=mapper)
+        jac_true = self.jac_vector_vector(x0)
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-5)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_4, jac_true, rtol=1e-12)
+
+    def test_wrong_dimensions(self):
+        x0 = 1.0
+        assert_raises(RuntimeError, approx_derivative,
+                      self.wrong_dimensions_fun, x0)
+        f0 = self.wrong_dimensions_fun(np.atleast_1d(x0))
+        assert_raises(ValueError, approx_derivative,
+                      self.wrong_dimensions_fun, x0, f0=f0)
+
+    def test_custom_rel_step(self):
+        x0 = np.array([-0.1, 0.1])
+        jac_diff_2 = approx_derivative(self.fun_vector_vector, x0,
+                                       method='2-point', rel_step=1e-4)
+        jac_diff_3 = approx_derivative(self.fun_vector_vector, x0,
+                                       rel_step=1e-4)
+        jac_true = self.jac_vector_vector(x0)
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-2)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-4)
+
+    def test_options(self):
+        x0 = np.array([1.0, 1.0])
+        c0 = -1.0
+        c1 = 1.0
+        lb = 0.0
+        ub = 2.0
+        f0 = self.fun_parametrized(x0, c0, c1=c1)
+        rel_step = np.array([-1e-6, 1e-7])
+        jac_true = self.jac_parametrized(x0, c0, c1)
+        jac_diff_2 = approx_derivative(
+            self.fun_parametrized, x0, method='2-point', rel_step=rel_step,
+            f0=f0, args=(c0,), kwargs=dict(c1=c1), bounds=(lb, ub))
+        jac_diff_3 = approx_derivative(
+            self.fun_parametrized, x0, rel_step=rel_step,
+            f0=f0, args=(c0,), kwargs=dict(c1=c1), bounds=(lb, ub))
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-9)
+
+    def test_with_bounds_2_point(self):
+        lb = -np.ones(2)
+        ub = np.ones(2)
+
+        x0 = np.array([-2.0, 0.2])
+        assert_raises(ValueError, approx_derivative,
+                      self.fun_vector_vector, x0, bounds=(lb, ub))
+
+        x0 = np.array([-1.0, 1.0])
+        jac_diff = approx_derivative(self.fun_vector_vector, x0,
+                                     method='2-point', bounds=(lb, ub))
+        jac_true = self.jac_vector_vector(x0)
+        assert_allclose(jac_diff, jac_true, rtol=1e-6)
+
+    def test_with_bounds_3_point(self):
+        lb = np.array([1.0, 1.0])
+        ub = np.array([2.0, 2.0])
+
+        x0 = np.array([1.0, 2.0])
+        jac_true = self.jac_vector_vector(x0)
+
+        jac_diff = approx_derivative(self.fun_vector_vector, x0)
+        assert_allclose(jac_diff, jac_true, rtol=1e-9)
+
+        jac_diff = approx_derivative(self.fun_vector_vector, x0,
+                                     bounds=(lb, np.inf))
+        assert_allclose(jac_diff, jac_true, rtol=1e-9)
+
+        jac_diff = approx_derivative(self.fun_vector_vector, x0,
+                                     bounds=(-np.inf, ub))
+        assert_allclose(jac_diff, jac_true, rtol=1e-9)
+
+        jac_diff = approx_derivative(self.fun_vector_vector, x0,
+                                     bounds=(lb, ub))
+        assert_allclose(jac_diff, jac_true, rtol=1e-9)
+
+    def test_tight_bounds(self):
+        x0 = np.array([10.0, 10.0])
+        lb = x0 - 3e-9
+        ub = x0 + 2e-9
+        jac_true = self.jac_vector_vector(x0)
+        jac_diff = approx_derivative(
+            self.fun_vector_vector, x0, method='2-point', bounds=(lb, ub))
+        assert_allclose(jac_diff, jac_true, rtol=1e-6)
+        jac_diff = approx_derivative(
+            self.fun_vector_vector, x0, method='2-point',
+            rel_step=1e-6, bounds=(lb, ub))
+        assert_allclose(jac_diff, jac_true, rtol=1e-6)
+
+        jac_diff = approx_derivative(
+            self.fun_vector_vector, x0, bounds=(lb, ub))
+        assert_allclose(jac_diff, jac_true, rtol=1e-6)
+        jac_diff = approx_derivative(
+            self.fun_vector_vector, x0, rel_step=1e-6, bounds=(lb, ub))
+        assert_allclose(jac_true, jac_diff, rtol=1e-6)
+
+    def test_bound_switches(self):
+        lb = -1e-8
+        ub = 1e-8
+        x0 = 0.0
+        jac_true = self.jac_with_nan(x0)
+        jac_diff_2 = approx_derivative(
+            self.fun_with_nan, x0, method='2-point', rel_step=1e-6,
+            bounds=(lb, ub))
+        jac_diff_3 = approx_derivative(
+            self.fun_with_nan, x0, rel_step=1e-6, bounds=(lb, ub))
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-9)
+
+        x0 = 1e-8
+        jac_true = self.jac_with_nan(x0)
+        jac_diff_2 = approx_derivative(
+            self.fun_with_nan, x0, method='2-point', rel_step=1e-6,
+            bounds=(lb, ub))
+        jac_diff_3 = approx_derivative(
+            self.fun_with_nan, x0, rel_step=1e-6, bounds=(lb, ub))
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-9)
+
+    def test_non_numpy(self):
+        x0 = 1.0
+        jac_true = self.jac_non_numpy(x0)
+        jac_diff_2 = approx_derivative(self.jac_non_numpy, x0,
+                                       method='2-point')
+        jac_diff_3 = approx_derivative(self.jac_non_numpy, x0)
+        assert_allclose(jac_diff_2, jac_true, rtol=1e-6)
+        assert_allclose(jac_diff_3, jac_true, rtol=1e-8)
+
+        # math.exp cannot handle complex arguments, hence this raises
+        assert_raises(TypeError, approx_derivative, self.jac_non_numpy, x0,
+                      **dict(method='cs'))
+
+    def test_fp(self):
+        # checks that approx_derivative works for FP size other than 64.
+        # Example is derived from the minimal working example in gh12991.
+        np.random.seed(1)
+
+        def func(p, x):
+            return p[0] + p[1] * x
+
+        def err(p, x, y):
+            return func(p, x) - y
+
+        x = np.linspace(0, 1, 100, dtype=np.float64)
+        y = np.random.random(100).astype(np.float64)
+        p0 = np.array([-1.0, -1.0])
+
+        jac_fp64 = approx_derivative(err, p0, method='2-point', args=(x, y))
+
+        # parameter vector is float32, func output is float64
+        jac_fp = approx_derivative(err, p0.astype(np.float32),
+                                   method='2-point', args=(x, y))
+        assert err(p0, x, y).dtype == np.float64
+        assert_allclose(jac_fp, jac_fp64, atol=1e-3)
+
+        # parameter vector is float64, func output is float32
+        def err_fp32(p):
+            assert p.dtype == np.float32
+            return err(p, x, y).astype(np.float32)
+
+        jac_fp = approx_derivative(err_fp32, p0.astype(np.float32),
+                                   method='2-point')
+        assert_allclose(jac_fp, jac_fp64, atol=1e-3)
+
+        # check upper bound of error on the derivative for 2-point
+        def f(x):
+            return np.sin(x)
+        def g(x):
+            return np.cos(x)
+        def hess(x):
+            return -np.sin(x)
+
+        def calc_atol(h, x0, f, hess, EPS):
+            # truncation error
+            t0 = h / 2 * max(np.abs(hess(x0)), np.abs(hess(x0 + h)))
+            # roundoff error. There may be a divisor (>1) missing from
+            # the following line, so this contribution is possibly
+            # overestimated
+            t1 = EPS / h * max(np.abs(f(x0)), np.abs(f(x0 + h)))
+            return t0 + t1
+
+        for dtype in [np.float16, np.float32, np.float64]:
+            EPS = np.finfo(dtype).eps
+            x0 = np.array(1.0).astype(dtype)
+            h = _compute_absolute_step(None, x0, f(x0), '2-point')
+            atol = calc_atol(h, x0, f, hess, EPS)
+            err = approx_derivative(f, x0, method='2-point',
+                                    abs_step=h) - g(x0)
+            assert abs(err) < atol
+
+    def test_check_derivative(self):
+        x0 = np.array([-10.0, 10])
+        accuracy = check_derivative(self.fun_vector_vector,
+                                    self.jac_vector_vector, x0)
+        assert_(accuracy < 1e-9)
+        accuracy = check_derivative(self.fun_vector_vector,
+                                    self.jac_vector_vector, x0)
+        assert_(accuracy < 1e-6)
+
+        x0 = np.array([0.0, 0.0])
+        accuracy = check_derivative(self.fun_zero_jacobian,
+                                    self.jac_zero_jacobian, x0)
+        assert_(accuracy == 0)
+        accuracy = check_derivative(self.fun_zero_jacobian,
+                                    self.jac_zero_jacobian, x0)
+        assert_(accuracy == 0)
+
+    def test_check_derivative_with_kwargs(self):
+        x0 = np.array([-10.0, 10])
+        accuracy = check_derivative(self.fun_vector_vector_with_arg,
+                                    self.jac_vector_vector_with_arg,
+                                    x0,
+                                    kwargs={'arg': 42})
+        assert_(accuracy < 1e-9)
+
+
+class TestApproxDerivativeSparse:
+    # Example from Numerical Optimization 2nd edition, p. 198.
+    def setup_method(self):
+        np.random.seed(0)
+        self.n = 50
+        self.lb = -0.1 * (1 + np.arange(self.n))
+        self.ub = 0.1 * (1 + np.arange(self.n))
+        self.x0 = np.empty(self.n)
+        self.x0[::2] = (1 - 1e-7) * self.lb[::2]
+        self.x0[1::2] = (1 - 1e-7) * self.ub[1::2]
+
+        self.J_true = self.jac(self.x0)
+
+    def fun(self, x):
+        e = x[1:]**3 - x[:-1]**2
+        return np.hstack((0, 3 * e)) + np.hstack((2 * e, 0))
+
+    def jac(self, x):
+        n = x.size
+        J = np.zeros((n, n))
+        J[0, 0] = -4 * x[0]
+        J[0, 1] = 6 * x[1]**2
+        for i in range(1, n - 1):
+            J[i, i - 1] = -6 * x[i-1]
+            J[i, i] = 9 * x[i]**2 - 4 * x[i]
+            J[i, i + 1] = 6 * x[i+1]**2
+        J[-1, -1] = 9 * x[-1]**2
+        J[-1, -2] = -6 * x[-2]
+
+        return J
+
+    def structure(self, n):
+        A = np.zeros((n, n), dtype=int)
+        A[0, 0] = 1
+        A[0, 1] = 1
+        for i in range(1, n - 1):
+            A[i, i - 1: i + 2] = 1
+        A[-1, -1] = 1
+        A[-1, -2] = 1
+
+        return A
+
+    @pytest.mark.fail_slow(5)
+    def test_all(self):
+        A = self.structure(self.n)
+        order = np.arange(self.n)
+        groups_1 = group_columns(A, order)
+        np.random.shuffle(order)
+        groups_2 = group_columns(A, order)
+
+        with MapWrapper(2) as mapper:
+            for method, groups, l, u, mf in product(
+                    ['2-point', '3-point', 'cs'], [groups_1, groups_2],
+                    [-np.inf, self.lb], [np.inf, self.ub], [map, mapper]):
+                J = approx_derivative(self.fun, self.x0, method=method,
+                                      bounds=(l, u), sparsity=(A, groups),
+                                      workers=mf)
+                assert_(isinstance(J, csr_array))
+                assert_allclose(J.toarray(), self.J_true, rtol=1e-6)
+
+                rel_step = np.full_like(self.x0, 1e-8)
+                rel_step[::2] *= -1
+                J = approx_derivative(self.fun, self.x0, method=method,
+                                      rel_step=rel_step, sparsity=(A, groups),
+                                      workers=mf)
+                assert_allclose(J.toarray(), self.J_true, rtol=1e-5)
+
+    def test_no_precomputed_groups(self):
+        A = self.structure(self.n)
+        J = approx_derivative(self.fun, self.x0, sparsity=A)
+        assert_allclose(J.toarray(), self.J_true, rtol=1e-6)
+
+    def test_equivalence(self):
+        structure = np.ones((self.n, self.n), dtype=int)
+        groups = np.arange(self.n)
+        for method in ['2-point', '3-point', 'cs']:
+            J_dense = approx_derivative(self.fun, self.x0, method=method)
+            J_sparse = approx_derivative(
+                self.fun, self.x0, sparsity=(structure, groups), method=method)
+            assert_allclose(J_dense, J_sparse.toarray(),
+                            rtol=5e-16, atol=7e-15)
+
+    def test_check_derivative(self):
+        def jac(x):
+            return csr_array(self.jac(x))
+
+        accuracy = check_derivative(self.fun, jac, self.x0,
+                                    bounds=(self.lb, self.ub))
+        assert_(accuracy < 1e-9)
+
+        accuracy = check_derivative(self.fun, jac, self.x0,
+                                    bounds=(self.lb, self.ub))
+        assert_(accuracy < 1e-9)
+
+
+class TestApproxDerivativeLinearOperator:
+
+    def fun_scalar_scalar(self, x):
+        return np.sinh(x)
+
+    def jac_scalar_scalar(self, x):
+        return np.cosh(x)
+
+    def fun_scalar_vector(self, x):
+        return np.array([x[0]**2, np.tan(x[0]), np.exp(x[0])])
+
+    def jac_scalar_vector(self, x):
+        return np.array(
+            [2 * x[0], np.cos(x[0]) ** -2, np.exp(x[0])]).reshape(-1, 1)
+
+    def fun_vector_scalar(self, x):
+        return np.sin(x[0] * x[1]) * np.log(x[0])
+
+    def jac_vector_scalar(self, x):
+        return np.array([
+            x[1] * np.cos(x[0] * x[1]) * np.log(x[0]) +
+            np.sin(x[0] * x[1]) / x[0],
+            x[0] * np.cos(x[0] * x[1]) * np.log(x[0])
+        ])
+
+    def fun_vector_vector(self, x):
+        return np.array([
+            x[0] * np.sin(x[1]),
+            x[1] * np.cos(x[0]),
+            x[0] ** 3 * x[1] ** -0.5
+        ])
+
+    def jac_vector_vector(self, x):
+        return np.array([
+            [np.sin(x[1]), x[0] * np.cos(x[1])],
+            [-x[1] * np.sin(x[0]), np.cos(x[0])],
+            [3 * x[0] ** 2 * x[1] ** -0.5, -0.5 * x[0] ** 3 * x[1] ** -1.5]
+        ])
+
+    def test_scalar_scalar(self):
+        x0 = 1.0
+        jac_diff_2 = approx_derivative(self.fun_scalar_scalar, x0,
+                                       method='2-point',
+                                       as_linear_operator=True)
+        jac_diff_3 = approx_derivative(self.fun_scalar_scalar, x0,
+                                       as_linear_operator=True)
+        jac_diff_4 = approx_derivative(self.fun_scalar_scalar, x0,
+                                       method='cs',
+                                       as_linear_operator=True)
+        jac_true = self.jac_scalar_scalar(x0)
+        np.random.seed(1)
+        for i in range(10):
+            p = np.random.uniform(-10, 10, size=(1,))
+            assert_allclose(jac_diff_2.dot(p), jac_true*p,
+                            rtol=1e-5)
+            assert_allclose(jac_diff_3.dot(p), jac_true*p,
+                            rtol=5e-6)
+            assert_allclose(jac_diff_4.dot(p), jac_true*p,
+                            rtol=5e-6)
+
+    def test_scalar_vector(self):
+        x0 = 0.5
+        jac_diff_2 = approx_derivative(self.fun_scalar_vector, x0,
+                                       method='2-point',
+                                       as_linear_operator=True)
+        jac_diff_3 = approx_derivative(self.fun_scalar_vector, x0,
+                                       as_linear_operator=True)
+        jac_diff_4 = approx_derivative(self.fun_scalar_vector, x0,
+                                       method='cs',
+                                       as_linear_operator=True)
+        jac_true = self.jac_scalar_vector(np.atleast_1d(x0))
+        np.random.seed(1)
+        for i in range(10):
+            p = np.random.uniform(-10, 10, size=(1,))
+            assert_allclose(jac_diff_2.dot(p), jac_true.dot(p),
+                            rtol=1e-5)
+            assert_allclose(jac_diff_3.dot(p), jac_true.dot(p),
+                            rtol=5e-6)
+            assert_allclose(jac_diff_4.dot(p), jac_true.dot(p),
+                            rtol=5e-6)
+
+    def test_vector_scalar(self):
+        x0 = np.array([100.0, -0.5])
+        jac_diff_2 = approx_derivative(self.fun_vector_scalar, x0,
+                                       method='2-point',
+                                       as_linear_operator=True)
+        jac_diff_3 = approx_derivative(self.fun_vector_scalar, x0,
+                                       as_linear_operator=True)
+        jac_diff_4 = approx_derivative(self.fun_vector_scalar, x0,
+                                       method='cs',
+                                       as_linear_operator=True)
+        jac_true = self.jac_vector_scalar(x0)
+        np.random.seed(1)
+        for i in range(10):
+            p = np.random.uniform(-10, 10, size=x0.shape)
+            assert_allclose(jac_diff_2.dot(p), np.atleast_1d(jac_true.dot(p)),
+                            rtol=1e-5)
+            assert_allclose(jac_diff_3.dot(p), np.atleast_1d(jac_true.dot(p)),
+                            rtol=5e-6)
+            assert_allclose(jac_diff_4.dot(p), np.atleast_1d(jac_true.dot(p)),
+                            rtol=1e-7)
+
+    def test_vector_vector(self):
+        x0 = np.array([-100.0, 0.2])
+        jac_diff_2 = approx_derivative(self.fun_vector_vector, x0,
+                                       method='2-point',
+                                       as_linear_operator=True)
+        jac_diff_3 = approx_derivative(self.fun_vector_vector, x0,
+                                       as_linear_operator=True)
+        jac_diff_4 = approx_derivative(self.fun_vector_vector, x0,
+                                       method='cs',
+                                       as_linear_operator=True)
+        jac_true = self.jac_vector_vector(x0)
+        np.random.seed(1)
+        for i in range(10):
+            p = np.random.uniform(-10, 10, size=x0.shape)
+            assert_allclose(jac_diff_2.dot(p), jac_true.dot(p), rtol=1e-5)
+            assert_allclose(jac_diff_3.dot(p), jac_true.dot(p), rtol=1e-6)
+            assert_allclose(jac_diff_4.dot(p), jac_true.dot(p), rtol=1e-7)
+
+    def test_exception(self):
+        x0 = np.array([-100.0, 0.2])
+        assert_raises(ValueError, approx_derivative,
+                      self.fun_vector_vector, x0,
+                      method='2-point', bounds=(1, np.inf))
+
+
+def test_absolute_step_sign():
+    # test for gh12487
+    # if an absolute step is specified for 2-point differences make sure that
+    # the side corresponds to the step. i.e. if step is positive then forward
+    # differences should be used, if step is negative then backwards
+    # differences should be used.
+
+    # function has double discontinuity at x = [-1, -1]
+    # first component is \/, second component is /\
+    def f(x):
+        return -np.abs(x[0] + 1) + np.abs(x[1] + 1)
+
+    # check that the forward difference is used
+    grad = approx_derivative(f, [-1, -1], method='2-point', abs_step=1e-8)
+    assert_allclose(grad, [-1.0, 1.0])
+
+    # check that the backwards difference is used
+    grad = approx_derivative(f, [-1, -1], method='2-point', abs_step=-1e-8)
+    assert_allclose(grad, [1.0, -1.0])
+
+    # check that the forwards difference is used with a step for both
+    # parameters
+    grad = approx_derivative(
+        f, [-1, -1], method='2-point', abs_step=[1e-8, 1e-8]
+    )
+    assert_allclose(grad, [-1.0, 1.0])
+
+    # check that we can mix forward/backwards steps.
+    grad = approx_derivative(
+        f, [-1, -1], method='2-point', abs_step=[1e-8, -1e-8]
+     )
+    assert_allclose(grad, [-1.0, -1.0])
+    grad = approx_derivative(
+        f, [-1, -1], method='2-point', abs_step=[-1e-8, 1e-8]
+    )
+    assert_allclose(grad, [1.0, 1.0])
+
+    # the forward step should reverse to a backwards step if it runs into a
+    # bound
+    # This is kind of tested in TestAdjustSchemeToBounds, but only for a lower level
+    # function.
+    grad = approx_derivative(
+        f, [-1, -1], method='2-point', abs_step=1e-8,
+        bounds=(-np.inf, -1)
+    )
+    assert_allclose(grad, [1.0, -1.0])
+
+    grad = approx_derivative(
+        f, [-1, -1], method='2-point', abs_step=-1e-8, bounds=(-1, np.inf)
+    )
+    assert_allclose(grad, [-1.0, 1.0])
+
+
+def test__compute_absolute_step():
+    # tests calculation of absolute step from rel_step
+    methods = ['2-point', '3-point', 'cs']
+
+    x0 = np.array([1e-5, 0, 1, 1e5])
+
+    EPS = np.finfo(np.float64).eps
+    relative_step = {
+        "2-point": EPS**0.5,
+        "3-point": EPS**(1/3),
+        "cs": EPS**0.5
+    }
+    f0 = np.array(1.0)
+
+    for method in methods:
+        rel_step = relative_step[method]
+        correct_step = np.array([rel_step,
+                                 rel_step * 1.,
+                                 rel_step * 1.,
+                                 rel_step * np.abs(x0[3])])
+
+        abs_step = _compute_absolute_step(None, x0, f0, method)
+        assert_allclose(abs_step, correct_step)
+
+        sign_x0 = (-x0 >= 0).astype(float) * 2 - 1
+        abs_step = _compute_absolute_step(None, -x0, f0, method)
+        assert_allclose(abs_step, sign_x0 * correct_step)
+
+    # if a relative step is provided it should be used
+    rel_step = np.array([0.1, 1, 10, 100])
+    correct_step = np.array([rel_step[0] * x0[0],
+                             relative_step['2-point'],
+                             rel_step[2] * 1.,
+                             rel_step[3] * np.abs(x0[3])])
+
+    abs_step = _compute_absolute_step(rel_step, x0, f0, '2-point')
+    assert_allclose(abs_step, correct_step)
+
+    sign_x0 = (-x0 >= 0).astype(float) * 2 - 1
+    abs_step = _compute_absolute_step(rel_step, -x0, f0, '2-point')
+    assert_allclose(abs_step, sign_x0 * correct_step)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test__remove_redundancy.py

@@ -0,0 +1,228 @@
+"""
+Unit test for Linear Programming via Simplex Algorithm.
+"""
+
+# TODO: add tests for:
+# https://github.com/scipy/scipy/issues/5400
+# https://github.com/scipy/scipy/issues/6690
+
+import numpy as np
+from numpy.testing import (
+    assert_,
+    assert_allclose,
+    assert_equal)
+
+from .test_linprog import magic_square
+from scipy.optimize._remove_redundancy import _remove_redundancy_svd
+from scipy.optimize._remove_redundancy import _remove_redundancy_pivot_dense
+from scipy.optimize._remove_redundancy import _remove_redundancy_pivot_sparse
+from scipy.optimize._remove_redundancy import _remove_redundancy_id
+
+from scipy.sparse import csc_array
+
+
+def setup_module():
+    np.random.seed(2017)
+
+
+def redundancy_removed(A, B):
+    """Checks whether a matrix contains only independent rows of another"""
+    for rowA in A:
+        # `rowA in B` is not a reliable check
+        for rowB in B:
+            if np.all(rowA == rowB):
+                break
+        else:
+            return False
+    return A.shape[0] == np.linalg.matrix_rank(A) == np.linalg.matrix_rank(B)
+
+
+class RRCommonTests:
+    def test_no_redundancy(self):
+        m, n = 10, 10
+        A0 = np.random.rand(m, n)
+        b0 = np.random.rand(m)
+        A1, b1, status, message = self.rr(A0, b0)
+        assert_allclose(A0, A1)
+        assert_allclose(b0, b1)
+        assert_equal(status, 0)
+
+    def test_infeasible_zero_row(self):
+        A = np.eye(3)
+        A[1, :] = 0
+        b = np.random.rand(3)
+        A1, b1, status, message = self.rr(A, b)
+        assert_equal(status, 2)
+
+    def test_remove_zero_row(self):
+        A = np.eye(3)
+        A[1, :] = 0
+        b = np.random.rand(3)
+        b[1] = 0
+        A1, b1, status, message = self.rr(A, b)
+        assert_equal(status, 0)
+        assert_allclose(A1, A[[0, 2], :])
+        assert_allclose(b1, b[[0, 2]])
+
+    def test_infeasible_m_gt_n(self):
+        m, n = 20, 10
+        A0 = np.random.rand(m, n)
+        b0 = np.random.rand(m)
+        A1, b1, status, message = self.rr(A0, b0)
+        assert_equal(status, 2)
+
+    def test_infeasible_m_eq_n(self):
+        m, n = 10, 10
+        A0 = np.random.rand(m, n)
+        b0 = np.random.rand(m)
+        A0[-1, :] = 2 * A0[-2, :]
+        A1, b1, status, message = self.rr(A0, b0)
+        assert_equal(status, 2)
+
+    def test_infeasible_m_lt_n(self):
+        m, n = 9, 10
+        A0 = np.random.rand(m, n)
+        b0 = np.random.rand(m)
+        A0[-1, :] = np.arange(m - 1).dot(A0[:-1])
+        A1, b1, status, message = self.rr(A0, b0)
+        assert_equal(status, 2)
+
+    def test_m_gt_n(self):
+        np.random.seed(2032)
+        m, n = 20, 10
+        A0 = np.random.rand(m, n)
+        b0 = np.random.rand(m)
+        x = np.linalg.solve(A0[:n, :], b0[:n])
+        b0[n:] = A0[n:, :].dot(x)
+        A1, b1, status, message = self.rr(A0, b0)
+        assert_equal(status, 0)
+        assert_equal(A1.shape[0], n)
+        assert_equal(np.linalg.matrix_rank(A1), n)
+
+    def test_m_gt_n_rank_deficient(self):
+        m, n = 20, 10
+        A0 = np.zeros((m, n))
+        A0[:, 0] = 1
+        b0 = np.ones(m)
+        A1, b1, status, message = self.rr(A0, b0)
+        assert_equal(status, 0)
+        assert_allclose(A1, A0[0:1, :])
+        assert_allclose(b1, b0[0])
+
+    def test_m_lt_n_rank_deficient(self):
+        m, n = 9, 10
+        A0 = np.random.rand(m, n)
+        b0 = np.random.rand(m)
+        A0[-1, :] = np.arange(m - 1).dot(A0[:-1])
+        b0[-1] = np.arange(m - 1).dot(b0[:-1])
+        A1, b1, status, message = self.rr(A0, b0)
+        assert_equal(status, 0)
+        assert_equal(A1.shape[0], 8)
+        assert_equal(np.linalg.matrix_rank(A1), 8)
+
+    def test_dense1(self):
+        A = np.ones((6, 6))
+        A[0, :3] = 0
+        A[1, 3:] = 0
+        A[3:, ::2] = -1
+        A[3, :2] = 0
+        A[4, 2:] = 0
+        b = np.zeros(A.shape[0])
+
+        A1, b1, status, message = self.rr(A, b)
+        assert_(redundancy_removed(A1, A))
+        assert_equal(status, 0)
+
+    def test_dense2(self):
+        A = np.eye(6)
+        A[-2, -1] = 1
+        A[-1, :] = 1
+        b = np.zeros(A.shape[0])
+        A1, b1, status, message = self.rr(A, b)
+        assert_(redundancy_removed(A1, A))
+        assert_equal(status, 0)
+
+    def test_dense3(self):
+        A = np.eye(6)
+        A[-2, -1] = 1
+        A[-1, :] = 1
+        b = np.random.rand(A.shape[0])
+        b[-1] = np.sum(b[:-1])
+        A1, b1, status, message = self.rr(A, b)
+        assert_(redundancy_removed(A1, A))
+        assert_equal(status, 0)
+
+    def test_m_gt_n_sparse(self):
+        np.random.seed(2013)
+        m, n = 20, 5
+        p = 0.1
+        A = np.random.rand(m, n)
+        A[np.random.rand(m, n) > p] = 0
+        rank = np.linalg.matrix_rank(A)
+        b = np.zeros(A.shape[0])
+        A1, b1, status, message = self.rr(A, b)
+        assert_equal(status, 0)
+        assert_equal(A1.shape[0], rank)
+        assert_equal(np.linalg.matrix_rank(A1), rank)
+
+    def test_m_lt_n_sparse(self):
+        np.random.seed(2017)
+        m, n = 20, 50
+        p = 0.05
+        A = np.random.rand(m, n)
+        A[np.random.rand(m, n) > p] = 0
+        rank = np.linalg.matrix_rank(A)
+        b = np.zeros(A.shape[0])
+        A1, b1, status, message = self.rr(A, b)
+        assert_equal(status, 0)
+        assert_equal(A1.shape[0], rank)
+        assert_equal(np.linalg.matrix_rank(A1), rank)
+
+    def test_m_eq_n_sparse(self):
+        np.random.seed(2017)
+        m, n = 100, 100
+        p = 0.01
+        A = np.random.rand(m, n)
+        A[np.random.rand(m, n) > p] = 0
+        rank = np.linalg.matrix_rank(A)
+        b = np.zeros(A.shape[0])
+        A1, b1, status, message = self.rr(A, b)
+        assert_equal(status, 0)
+        assert_equal(A1.shape[0], rank)
+        assert_equal(np.linalg.matrix_rank(A1), rank)
+
+    def test_magic_square(self):
+        A, b, c, numbers, _ = magic_square(3)
+        A1, b1, status, message = self.rr(A, b)
+        assert_equal(status, 0)
+        assert_equal(A1.shape[0], 23)
+        assert_equal(np.linalg.matrix_rank(A1), 23)
+
+    def test_magic_square2(self):
+        A, b, c, numbers, _ = magic_square(4)
+        A1, b1, status, message = self.rr(A, b)
+        assert_equal(status, 0)
+        assert_equal(A1.shape[0], 39)
+        assert_equal(np.linalg.matrix_rank(A1), 39)
+
+
+class TestRRSVD(RRCommonTests):
+    def rr(self, A, b):
+        return _remove_redundancy_svd(A, b)
+
+
+class TestRRPivotDense(RRCommonTests):
+    def rr(self, A, b):
+        return _remove_redundancy_pivot_dense(A, b)
+
+
+class TestRRID(RRCommonTests):
+    def rr(self, A, b):
+        return _remove_redundancy_id(A, b)
+
+
+class TestRRPivotSparse(RRCommonTests):
+    def rr(self, A, b):
+        rr_res = _remove_redundancy_pivot_sparse(csc_array(A), b)
+        A1, b1, status, message = rr_res
+        return A1.toarray(), b1, status, message

venv/lib/python3.13/site-packages/scipy/optimize/tests/test__root.py

@@ -0,0 +1,124 @@
+"""
+Unit tests for optimization routines from _root.py.
+"""
+from numpy.testing import assert_, assert_equal
+import pytest
+from pytest import raises as assert_raises, warns as assert_warns
+import numpy as np
+
+from scipy.optimize import root
+
+
+class TestRoot:
+    def test_tol_parameter(self):
+        # Check that the minimize() tol= argument does something
+        def func(z):
+            x, y = z
+            return np.array([x**3 - 1, y**3 - 1])
+
+        def dfunc(z):
+            x, y = z
+            return np.array([[3*x**2, 0], [0, 3*y**2]])
+
+        for method in ['hybr', 'lm', 'broyden1', 'broyden2', 'anderson',
+                       'diagbroyden', 'krylov']:
+            if method in ('linearmixing', 'excitingmixing'):
+                # doesn't converge
+                continue
+
+            if method in ('hybr', 'lm'):
+                jac = dfunc
+            else:
+                jac = None
+
+            sol1 = root(func, [1.1,1.1], jac=jac, tol=1e-4, method=method)
+            sol2 = root(func, [1.1,1.1], jac=jac, tol=0.5, method=method)
+            msg = f"{method}: {func(sol1.x)} vs. {func(sol2.x)}"
+            assert_(sol1.success, msg)
+            assert_(sol2.success, msg)
+            assert_(abs(func(sol1.x)).max() < abs(func(sol2.x)).max(),
+                    msg)
+
+    def test_tol_norm(self):
+
+        def norm(x):
+            return abs(x[0])
+
+        for method in ['excitingmixing',
+                       'diagbroyden',
+                       'linearmixing',
+                       'anderson',
+                       'broyden1',
+                       'broyden2',
+                       'krylov']:
+
+            root(np.zeros_like, np.zeros(2), method=method,
+                options={"tol_norm": norm})
+
+    def test_minimize_scalar_coerce_args_param(self):
+        # GitHub issue #3503
+        def func(z, f=1):
+            x, y = z
+            return np.array([x**3 - 1, y**3 - f])
+        root(func, [1.1, 1.1], args=1.5)
+
+    def test_f_size(self):
+        # gh8320
+        # check that decreasing the size of the returned array raises an error
+        # and doesn't segfault
+        class fun:
+            def __init__(self):
+                self.count = 0
+
+            def __call__(self, x):
+                self.count += 1
+
+                if not (self.count % 5):
+                    ret = x[0] + 0.5 * (x[0] - x[1]) ** 3 - 1.0
+                else:
+                    ret = ([x[0] + 0.5 * (x[0] - x[1]) ** 3 - 1.0,
+                           0.5 * (x[1] - x[0]) ** 3 + x[1]])
+
+                return ret
+
+        F = fun()
+        with assert_raises(ValueError):
+            root(F, [0.1, 0.0], method='lm')
+
+    @pytest.mark.thread_unsafe
+    def test_gh_10370(self):
+        # gh-10370 reported that passing both `args` and `jac` to `root` with
+        # `method='krylov'` caused a failure. Ensure that this is fixed whether
+        # the gradient is passed via `jac` or as a second output of `fun`.
+        def fun(x, ignored):
+            return [3*x[0] - 0.25*x[1]**2 + 10, 0.1*x[0]**2 + 5*x[1] - 2]
+
+        def grad(x, ignored):
+            return [[3, 0.5 * x[1]], [0.2 * x[0], 5]]
+
+        def fun_grad(x, ignored):
+            return fun(x, ignored), grad(x, ignored)
+
+        x0 = np.zeros(2)
+
+        ref = root(fun, x0, args=(1,), method='krylov')
+        message = 'Method krylov does not use the jacobian'
+        with assert_warns(RuntimeWarning, match=message):
+            res1 = root(fun, x0, args=(1,), method='krylov', jac=grad)
+        with assert_warns(RuntimeWarning, match=message):
+            res2 = root(fun_grad, x0, args=(1,), method='krylov', jac=True)
+
+        assert_equal(res1.x, ref.x)
+        assert_equal(res2.x, ref.x)
+        assert res1.success is res2.success is ref.success is True
+
+    @pytest.mark.parametrize("method", ["hybr", "lm", "broyden1", "broyden2",
+                                        "anderson", "linearmixing",
+                                        "diagbroyden", "excitingmixing",
+                                        "krylov", "df-sane"])
+    def test_method_in_result(self, method):
+        def func(x):
+            return x - 1
+
+        res = root(func, x0=[1], method=method)
+        assert res.method == method

venv/lib/python3.13/site-packages/scipy/optimize/tests/test__spectral.py

@@ -0,0 +1,226 @@
+import itertools
+
+import numpy as np
+from numpy import exp
+from numpy.testing import assert_, assert_equal
+
+from scipy.optimize import root
+
+
+def test_performance():
+    # Compare performance results to those listed in
+    # [Cheng & Li, IMA J. Num. An. 29, 814 (2008)]
+    # and
+    # [W. La Cruz, J.M. Martinez, M. Raydan, Math. Comp. 75, 1429 (2006)].
+    # and those produced by dfsane.f from M. Raydan's website.
+    #
+    # Where the results disagree, the largest limits are taken.
+
+    e_a = 1e-5
+    e_r = 1e-4
+
+    table_1 = [
+        dict(F=F_1, x0=x0_1, n=1000, nit=5, nfev=5),
+        dict(F=F_1, x0=x0_1, n=10000, nit=2, nfev=2),
+        dict(F=F_2, x0=x0_2, n=500, nit=11, nfev=11),
+        dict(F=F_2, x0=x0_2, n=2000, nit=11, nfev=11),
+        # dict(F=F_4, x0=x0_4, n=999, nit=243, nfev=1188) removed:
+        # too sensitive to rounding errors
+        # Results from dfsane.f; papers list nit=3, nfev=3
+        dict(F=F_6, x0=x0_6, n=100, nit=6, nfev=6),
+        # Must have n%3==0, typo in papers?
+        dict(F=F_7, x0=x0_7, n=99, nit=23, nfev=29),
+        # Must have n%3==0, typo in papers?
+        dict(F=F_7, x0=x0_7, n=999, nit=23, nfev=29),
+        # Results from dfsane.f; papers list nit=nfev=6?
+        dict(F=F_9, x0=x0_9, n=100, nit=12, nfev=18),
+        dict(F=F_9, x0=x0_9, n=1000, nit=12, nfev=18),
+        # Results from dfsane.f; papers list nit=2, nfev=12
+        dict(F=F_10, x0=x0_10, n=1000, nit=5, nfev=5),
+    ]
+
+    # Check also scaling invariance
+    for xscale, yscale, line_search in itertools.product(
+        [1.0, 1e-10, 1e10], [1.0, 1e-10, 1e10], ['cruz', 'cheng']
+    ):
+        for problem in table_1:
+            n = problem['n']
+            def func(x, n):
+                return yscale * problem['F'](x / xscale, n)
+            args = (n,)
+            x0 = problem['x0'](n) * xscale
+
+            fatol = np.sqrt(n) * e_a * yscale + e_r * np.linalg.norm(func(x0, n))
+
+            sigma_eps = 1e-10 * min(yscale/xscale, xscale/yscale)
+            sigma_0 = xscale/yscale
+
+            with np.errstate(over='ignore'):
+                sol = root(func, x0, args=args,
+                           options=dict(ftol=0, fatol=fatol, maxfev=problem['nfev'] + 1,
+                                        sigma_0=sigma_0, sigma_eps=sigma_eps,
+                                        line_search=line_search),
+                           method='DF-SANE')
+
+            err_msg = repr(
+                [xscale, yscale, line_search, problem, np.linalg.norm(func(sol.x, n)),
+                 fatol, sol.success, sol.nit, sol.nfev]
+            )
+            assert sol.success, err_msg
+            # nfev+1: dfsane.f doesn't count first eval
+            assert sol.nfev <= problem['nfev'] + 1, err_msg
+            assert sol.nit <= problem['nit'], err_msg
+            assert np.linalg.norm(func(sol.x, n)) <= fatol, err_msg
+
+
+def test_complex():
+    def func(z):
+        return z**2 - 1 + 2j
+    x0 = 2.0j
+
+    ftol = 1e-4
+    sol = root(func, x0, tol=ftol, method='DF-SANE')
+
+    assert_(sol.success)
+
+    f0 = np.linalg.norm(func(x0))
+    fx = np.linalg.norm(func(sol.x))
+    assert_(fx <= ftol*f0)
+
+
+def test_linear_definite():
+    # The DF-SANE paper proves convergence for "strongly isolated"
+    # solutions.
+    #
+    # For linear systems F(x) = A x - b = 0, with A positive or
+    # negative definite, the solution is strongly isolated.
+
+    def check_solvability(A, b, line_search='cruz'):
+        def func(x):
+            return A.dot(x) - b
+        xp = np.linalg.solve(A, b)
+        eps = np.linalg.norm(func(xp)) * 1e3
+        sol = root(
+            func, b,
+            options=dict(fatol=eps, ftol=0, maxfev=17523, line_search=line_search),
+            method='DF-SANE',
+        )
+        assert_(sol.success)
+        assert_(np.linalg.norm(func(sol.x)) <= eps)
+
+    n = 90
+
+    # Test linear pos.def. system
+    np.random.seed(1234)
+    A = np.arange(n*n).reshape(n, n)
+    A = A + n*n * np.diag(1 + np.arange(n))
+    assert_(np.linalg.eigvals(A).min() > 0)
+    b = np.arange(n) * 1.0
+    check_solvability(A, b, 'cruz')
+    check_solvability(A, b, 'cheng')
+
+    # Test linear neg.def. system
+    check_solvability(-A, b, 'cruz')
+    check_solvability(-A, b, 'cheng')
+
+
+def test_shape():
+    def f(x, arg):
+        return x - arg
+
+    for dt in [float, complex]:
+        x = np.zeros([2,2])
+        arg = np.ones([2,2], dtype=dt)
+
+        sol = root(f, x, args=(arg,), method='DF-SANE')
+        assert_(sol.success)
+        assert_equal(sol.x.shape, x.shape)
+
+
+# Some of the test functions and initial guesses listed in
+# [W. La Cruz, M. Raydan. Optimization Methods and Software, 18, 583 (2003)]
+
+def F_1(x, n):
+    g = np.zeros([n])
+    i = np.arange(2, n+1)
+    g[0] = exp(x[0] - 1) - 1
+    g[1:] = i*(exp(x[1:] - 1) - x[1:])
+    return g
+
+def x0_1(n):
+    x0 = np.empty([n])
+    x0.fill(n/(n-1))
+    return x0
+
+def F_2(x, n):
+    g = np.zeros([n])
+    i = np.arange(2, n+1)
+    g[0] = exp(x[0]) - 1
+    g[1:] = 0.1*i*(exp(x[1:]) + x[:-1] - 1)
+    return g
+
+def x0_2(n):
+    x0 = np.empty([n])
+    x0.fill(1/n**2)
+    return x0
+
+
+def F_4(x, n):  # skip name check
+    assert_equal(n % 3, 0)
+    g = np.zeros([n])
+    # Note: the first line is typoed in some of the references;
+    # correct in original [Gasparo, Optimization Meth. 13, 79 (2000)]
+    g[::3] = 0.6 * x[::3] + 1.6 * x[1::3]**3 - 7.2 * x[1::3]**2 + 9.6 * x[1::3] - 4.8
+    g[1::3] = (0.48 * x[::3] - 0.72 * x[1::3]**3 + 3.24 * x[1::3]**2 - 4.32 * x[1::3]
+               - x[2::3] + 0.2 * x[2::3]**3 + 2.16)
+    g[2::3] = 1.25 * x[2::3] - 0.25*x[2::3]**3
+    return g
+
+
+def x0_4(n):  # skip name check
+    assert_equal(n % 3, 0)
+    x0 = np.array([-1, 1/2, -1] * (n//3))
+    return x0
+
+def F_6(x, n):
+    c = 0.9
+    mu = (np.arange(1, n+1) - 0.5)/n
+    return x - 1/(1 - c/(2*n) * (mu[:,None]*x / (mu[:,None] + mu)).sum(axis=1))
+
+def x0_6(n):
+    return np.ones([n])
+
+def F_7(x, n):
+    assert_equal(n % 3, 0)
+
+    def phi(t):
+        v = 0.5*t - 2
+        v[t > -1] = ((-592*t**3 + 888*t**2 + 4551*t - 1924)/1998)[t > -1]
+        v[t >= 2] = (0.5*t + 2)[t >= 2]
+        return v
+    g = np.zeros([n])
+    g[::3] = 1e4 * x[1::3]**2 - 1
+    g[1::3] = exp(-x[::3]) + exp(-x[1::3]) - 1.0001
+    g[2::3] = phi(x[2::3])
+    return g
+
+def x0_7(n):
+    assert_equal(n % 3, 0)
+    return np.array([1e-3, 18, 1] * (n//3))
+
+def F_9(x, n):
+    g = np.zeros([n])
+    i = np.arange(2, n)
+    g[0] = x[0]**3/3 + x[1]**2/2
+    g[1:-1] = -x[1:-1]**2/2 + i*x[1:-1]**3/3 + x[2:]**2/2
+    g[-1] = -x[-1]**2/2 + n*x[-1]**3/3
+    return g
+
+def x0_9(n):
+    return np.ones([n])
+
+def F_10(x, n):
+    return np.log(1 + x) - x/n
+
+def x0_10(n):
+    return np.ones([n])

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_bracket.py

@@ -0,0 +1,896 @@
+import pytest
+
+import numpy as np
+
+from scipy.optimize._bracket import _ELIMITS
+from scipy.optimize.elementwise import bracket_root, bracket_minimum
+import scipy._lib._elementwise_iterative_method as eim
+from scipy import stats
+from scipy._lib._array_api_no_0d import (xp_assert_close, xp_assert_equal,
+                                         xp_assert_less)
+from scipy._lib._array_api import xp_ravel
+
+
+# These tests were originally written for the private `optimize._bracket`
+# interfaces, but now we want the tests to check the behavior of the public
+# `optimize.elementwise` interfaces. Therefore, rather than importing
+# `_bracket_root`/`_bracket_minimum` from `_bracket.py`, we import
+# `bracket_root`/`bracket_minimum` from `optimize.elementwise` and wrap those
+# functions to conform to the private interface. This may look a little strange,
+# since it effectively just inverts the interface transformation done within the
+# `bracket_root`/`bracket_minimum` functions, but it allows us to run the original,
+# unmodified tests on the public interfaces, simplifying the PR that adds
+# the public interfaces. We'll refactor this when we want to @parametrize the
+# tests over multiple `method`s.
+def _bracket_root(*args, **kwargs):
+    res = bracket_root(*args, **kwargs)
+    res.xl, res.xr = res.bracket
+    res.fl, res.fr = res.f_bracket
+    del res.bracket
+    del res.f_bracket
+    return res
+
+
+def _bracket_minimum(*args, **kwargs):
+    res = bracket_minimum(*args, **kwargs)
+    res.xl, res.xm, res.xr = res.bracket
+    res.fl, res.fm, res.fr = res.f_bracket
+    del res.bracket
+    del res.f_bracket
+    return res
+
+
+array_api_strict_skip_reason = 'Array API does not support fancy indexing assignment.'
+boolean_index_skip_reason = 'JAX/Dask arrays do not support boolean assignment.'
+
+@pytest.mark.skip_xp_backends('array_api_strict', reason=array_api_strict_skip_reason)
+@pytest.mark.skip_xp_backends('jax.numpy', reason=boolean_index_skip_reason)
+@pytest.mark.skip_xp_backends('dask.array', reason=boolean_index_skip_reason)
+class TestBracketRoot:
+    @pytest.mark.parametrize("seed", (615655101, 3141866013, 238075752))
+    @pytest.mark.parametrize("use_xmin", (False, True))
+    @pytest.mark.parametrize("other_side", (False, True))
+    @pytest.mark.parametrize("fix_one_side", (False, True))
+    def test_nfev_expected(self, seed, use_xmin, other_side, fix_one_side, xp):
+        # Property-based test to confirm that _bracket_root is behaving as
+        # expected. The basic case is when root < a < b.
+        # The number of times bracket expands (per side) can be found by
+        # setting the expression for the left endpoint of the bracket to the
+        # root of f (x=0), solving for i, and rounding up. The corresponding
+        # lower and upper ends of the bracket are found by plugging this back
+        # into the expression for the ends of the bracket.
+        # `other_side=True` is the case that a < b < root
+        # Special cases like a < root < b are tested separately
+        rng = np.random.default_rng(seed)
+        xl0, d, factor = xp.asarray(rng.random(size=3) * [1e5, 10, 5])
+        factor = 1 + factor  # factor must be greater than 1
+        xr0 = xl0 + d  # xr0 must be greater than a in basic case
+
+        def f(x):
+            f.count += 1
+            return x  # root is 0
+
+        if use_xmin:
+            xmin = xp.asarray(-rng.random())
+            n = xp.ceil(xp.log(-(xl0 - xmin) / xmin) / xp.log(factor))
+            l, u = xmin + (xl0 - xmin)*factor**-n, xmin + (xl0 - xmin)*factor**-(n - 1)
+            kwargs = dict(xl0=xl0, xr0=xr0, factor=factor, xmin=xmin)
+        else:
+            n = xp.ceil(xp.log(xr0/d) / xp.log(factor))
+            l, u = xr0 - d*factor**n, xr0 - d*factor**(n-1)
+            kwargs = dict(xl0=xl0, xr0=xr0, factor=factor)
+
+        if other_side:
+            kwargs['xl0'], kwargs['xr0'] = -kwargs['xr0'], -kwargs['xl0']
+            l, u = -u, -l
+            if 'xmin' in kwargs:
+                kwargs['xmax'] = -kwargs.pop('xmin')
+
+        if fix_one_side:
+            if other_side:
+                kwargs['xmin'] = -xr0
+            else:
+                kwargs['xmax'] = xr0
+
+        f.count = 0
+        res = _bracket_root(f, **kwargs)
+
+        # Compare reported number of function evaluations `nfev` against
+        # reported `nit`, actual function call count `f.count`, and theoretical
+        # number of expansions `n`.
+        # When both sides are free, these get multiplied by 2 because function
+        # is evaluated on the left and the right each iteration.
+        # When one side is fixed, however, we add one: on the right side, the
+        # function gets evaluated once at b.
+        # Add 1 to `n` and `res.nit` because function evaluations occur at
+        # iterations *0*, 1, ..., `n`. Subtract 1 from `f.count` because
+        # function is called separately for left and right in iteration 0.
+        if not fix_one_side:
+            assert res.nfev == 2*(res.nit+1) == 2*(f.count-1) == 2*(n + 1)
+        else:
+            assert res.nfev == (res.nit+1)+1 == (f.count-1)+1 == (n+1)+1
+
+        # Compare reported bracket to theoretical bracket and reported function
+        # values to function evaluated at bracket.
+        bracket = xp.asarray([res.xl, res.xr])
+        xp_assert_close(bracket, xp.asarray([l, u]))
+        f_bracket = xp.asarray([res.fl, res.fr])
+        xp_assert_close(f_bracket, f(bracket))
+
+        # Check that bracket is valid and that status and success are correct
+        assert res.xr > res.xl
+        signs = xp.sign(f_bracket)
+        assert signs[0] == -signs[1]
+        assert res.status == 0
+        assert res.success
+
+    def f(self, q, p):
+        return stats._stats_py._SimpleNormal().cdf(q) - p
+
+    @pytest.mark.parametrize('p', [0.6, np.linspace(0.05, 0.95, 10)])
+    @pytest.mark.parametrize('xmin', [-5, None])
+    @pytest.mark.parametrize('xmax', [5, None])
+    @pytest.mark.parametrize('factor', [1.2, 2])
+    def test_basic(self, p, xmin, xmax, factor, xp):
+        # Test basic functionality to bracket root (distribution PPF)
+        res = _bracket_root(self.f, xp.asarray(-0.01), 0.01, xmin=xmin, xmax=xmax,
+                            factor=factor, args=(xp.asarray(p),))
+        xp_assert_equal(-xp.sign(res.fl), xp.sign(res.fr))
+
+    @pytest.mark.parametrize('shape', [tuple(), (12,), (3, 4), (3, 2, 2)])
+    def test_vectorization(self, shape, xp):
+        # Test for correct functionality, output shapes, and dtypes for various
+        # input shapes.
+        p = np.linspace(-0.05, 1.05, 12).reshape(shape) if shape else np.float64(0.6)
+        args = (p,)
+        maxiter = 10
+
+        @np.vectorize
+        def bracket_root_single(xl0, xr0, xmin, xmax, factor, p):
+            return _bracket_root(self.f, xl0, xr0, xmin=xmin, xmax=xmax,
+                                 factor=factor, args=(p,),
+                                 maxiter=maxiter)
+
+        def f(*args, **kwargs):
+            f.f_evals += 1
+            return self.f(*args, **kwargs)
+        f.f_evals = 0
+
+        rng = np.random.default_rng(2348234)
+        xl0 = -rng.random(size=shape)
+        xr0 = rng.random(size=shape)
+        xmin, xmax = 1e3*xl0, 1e3*xr0
+        if shape:  # make some elements un
+            i = rng.random(size=shape) > 0.5
+            xmin[i], xmax[i] = -np.inf, np.inf
+        factor = rng.random(size=shape) + 1.5
+        refs = bracket_root_single(xl0, xr0, xmin, xmax, factor, p).ravel()
+        xl0, xr0, xmin, xmax, factor = (xp.asarray(xl0), xp.asarray(xr0),
+                                        xp.asarray(xmin), xp.asarray(xmax),
+                                        xp.asarray(factor))
+        args = tuple(map(xp.asarray, args))
+        res = _bracket_root(f, xl0, xr0, xmin=xmin, xmax=xmax, factor=factor,
+                            args=args, maxiter=maxiter)
+
+        attrs = ['xl', 'xr', 'fl', 'fr', 'success', 'nfev', 'nit']
+        for attr in attrs:
+            ref_attr = [xp.asarray(getattr(ref, attr)) for ref in refs]
+            res_attr = getattr(res, attr)
+            xp_assert_close(xp_ravel(res_attr, xp=xp), xp.stack(ref_attr))
+            assert res_attr.shape == shape
+
+        assert res.success.dtype == xp.bool
+        if shape:
+            assert xp.all(res.success[1:-1])
+        assert res.status.dtype == xp.int32
+        assert res.nfev.dtype == xp.int32
+        assert res.nit.dtype == xp.int32
+        assert xp.max(res.nit) == f.f_evals - 2
+        xp_assert_less(res.xl, res.xr)
+        xp_assert_close(res.fl, xp.asarray(self.f(res.xl, *args)))
+        xp_assert_close(res.fr, xp.asarray(self.f(res.xr, *args)))
+
+    def test_flags(self, xp):
+        # Test cases that should produce different status flags; show that all
+        # can be produced simultaneously.
+        def f(xs, js):
+            funcs = [lambda x: x - 1.5,
+                     lambda x: x - 1000,
+                     lambda x: x - 1000,
+                     lambda x: x * xp.nan,
+                     lambda x: x]
+
+            return [funcs[int(j)](x) for x, j in zip(xs, js)]
+
+        args = (xp.arange(5, dtype=xp.int64),)
+        res = _bracket_root(f,
+                            xl0=xp.asarray([-1., -1., -1., -1., 4.]),
+                            xr0=xp.asarray([1, 1, 1, 1, -4]),
+                            xmin=xp.asarray([-xp.inf, -1, -xp.inf, -xp.inf, 6]),
+                            xmax=xp.asarray([xp.inf, 1, xp.inf, xp.inf, 2]),
+                            args=args, maxiter=3)
+
+        ref_flags = xp.asarray([eim._ECONVERGED,
+                                _ELIMITS,
+                                eim._ECONVERR,
+                                eim._EVALUEERR,
+                                eim._EINPUTERR],
+                               dtype=xp.int32)
+
+        xp_assert_equal(res.status, ref_flags)
+
+    @pytest.mark.parametrize("root", (0.622, [0.622, 0.623]))
+    @pytest.mark.parametrize('xmin', [-5, None])
+    @pytest.mark.parametrize('xmax', [5, None])
+    @pytest.mark.parametrize("dtype", ("float16", "float32", "float64"))
+    def test_dtype(self, root, xmin, xmax, dtype, xp):
+        # Test that dtypes are preserved
+        dtype = getattr(xp, dtype)
+        xmin = xmin if xmin is None else xp.asarray(xmin, dtype=dtype)
+        xmax = xmax if xmax is None else xp.asarray(xmax, dtype=dtype)
+        root = xp.asarray(root, dtype=dtype)
+        def f(x, root):
+            return xp.astype((x - root) ** 3, dtype)
+
+        bracket = xp.asarray([-0.01, 0.01], dtype=dtype)
+        res = _bracket_root(f, *bracket, xmin=xmin, xmax=xmax, args=(root,))
+        assert xp.all(res.success)
+        assert res.xl.dtype == res.xr.dtype == dtype
+        assert res.fl.dtype == res.fr.dtype == dtype
+
+    def test_input_validation(self, xp):
+        # Test input validation for appropriate error messages
+
+        message = '`func` must be callable.'
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(None, -4, 4)
+
+        message = '...must be numeric and real.'
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4+1j, 4)
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4, 4+1j)
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4, 4, xmin=4+1j)
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4, 4, xmax=4+1j)
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4, 4, factor=4+1j)
+
+        message = "All elements of `factor` must be greater than 1."
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4, 4, factor=0.5)
+
+        message = "broadcast"
+        # raised by `xp.broadcast, but the traceback is readable IMO
+        with pytest.raises(Exception, match=message):
+            _bracket_root(lambda x: x, xp.asarray([-2, -3]), xp.asarray([3, 4, 5]))
+        # Consider making this give a more readable error message
+        # with pytest.raises(ValueError, match=message):
+        #     _bracket_root(lambda x: [x[0], x[1], x[1]], [-3, -3], [5, 5])
+
+        message = '`maxiter` must be a non-negative integer.'
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4, 4, maxiter=1.5)
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4, 4, maxiter=-1)
+        with pytest.raises(ValueError, match=message):
+            _bracket_root(lambda x: x, -4, 4, maxiter="shrubbery")
+
+    def test_special_cases(self, xp):
+        # Test edge cases and other special cases
+        # Test that integers are not passed to `f`
+        # (otherwise this would overflow)
+        def f(x):
+            assert xp.isdtype(x.dtype, "real floating")
+            return x ** 99 - 1
+
+        res = _bracket_root(f, xp.asarray(-7.), xp.asarray(5.))
+        assert res.success
+
+        # Test maxiter = 0. Should do nothing to bracket.
+        def f(x):
+            return x - 10
+
+        bracket = (xp.asarray(-3.), xp.asarray(5.))
+        res = _bracket_root(f, *bracket, maxiter=0)
+        assert res.xl, res.xr == bracket
+        assert res.nit == 0
+        assert res.nfev == 2
+        assert res.status == -2
+
+        # Test scalar `args` (not in tuple)
+        def f(x, c):
+            return c*x - 1
+
+        res = _bracket_root(f, xp.asarray(-1.), xp.asarray(1.),
+                            args=xp.asarray(3.))
+        assert res.success
+        xp_assert_close(res.fl, f(res.xl, 3))
+
+        # Test other edge cases
+
+        def f(x):
+            f.count += 1
+            return x
+
+        # 1. root lies within guess of bracket
+        f.count = 0
+        _bracket_root(f, xp.asarray(-10), xp.asarray(20))
+        assert f.count == 2
+
+        # 2. bracket endpoint hits root exactly
+        f.count = 0
+        res = _bracket_root(f, xp.asarray(5.), xp.asarray(10.),
+                            factor=2)
+
+        assert res.nfev == 4
+        xp_assert_close(res.xl, xp.asarray(0.), atol=1e-15)
+        xp_assert_close(res.xr, xp.asarray(5.), atol=1e-15)
+
+        # 3. bracket limit hits root exactly
+        with np.errstate(over='ignore'):
+            res = _bracket_root(f, xp.asarray(5.), xp.asarray(10.),
+                                xmin=0)
+        xp_assert_close(res.xl, xp.asarray(0.), atol=1e-15)
+
+        with np.errstate(over='ignore'):
+            res = _bracket_root(f, xp.asarray(-10.), xp.asarray(-5.),
+                                xmax=0)
+        xp_assert_close(res.xr, xp.asarray(0.), atol=1e-15)
+
+        # 4. bracket not within min, max
+        with np.errstate(over='ignore'):
+            res = _bracket_root(f, xp.asarray(5.), xp.asarray(10.),
+                                xmin=1)
+        assert not res.success
+
+    def test_bug_fixes(self):
+        # 1. Bug in double sided bracket search.
+        # Happened in some cases where there are terminations on one side
+        # after corresponding searches on other side failed due to reaching the
+        # boundary.
+
+        # https://github.com/scipy/scipy/pull/22560#discussion_r1962853839
+        def f(x, p):
+            return np.exp(x) - p
+
+        p = np.asarray([0.29, 0.35])
+        res = _bracket_root(f, xl0=-1, xmin=-np.inf, xmax=0, args=(p, ))
+
+        # https://github.com/scipy/scipy/pull/22560/files#r1962952517
+        def f(x, p, c):
+            return np.exp(x*c) - p
+
+        p = [0.32061201, 0.39175242, 0.40047535, 0.50527218, 0.55654373,
+             0.11911647, 0.37507896, 0.66554191]
+        c = [1., -1., 1., 1., -1., 1., 1., 1.]
+        xl0 = [-7.63108551,  3.27840947, -8.36968526, -1.78124372,
+               0.92201295, -2.48930123, -0.66733533, -0.44606749]
+        xr0 = [-6.63108551,  4.27840947, -7.36968526, -0.78124372,
+               1.92201295, -1.48930123, 0., 0.]
+        xmin = [-np.inf, 0., -np.inf, -np.inf, 0., -np.inf, -np.inf,
+                -np.inf]
+        xmax = [0., np.inf, 0., 0., np.inf, 0., 0., 0.]
+
+        res = _bracket_root(f, xl0=xl0, xr0=xr0, xmin=xmin, xmax=xmax, args=(p, c))
+
+        # 2. Default xl0 + 1 for xr0 exceeds xmax.
+        # https://github.com/scipy/scipy/pull/22560#discussion_r1962947434
+        res = _bracket_root(lambda x: x + 0.25, xl0=-0.5, xmin=-np.inf, xmax=0)
+        assert res.success
+
+
+@pytest.mark.skip_xp_backends('torch', reason='data-apis/array-api-compat#271')
+@pytest.mark.skip_xp_backends('array_api_strict', reason=array_api_strict_skip_reason)
+@pytest.mark.skip_xp_backends('jax.numpy', reason=boolean_index_skip_reason)
+@pytest.mark.skip_xp_backends('dask.array', reason=boolean_index_skip_reason)
+class TestBracketMinimum:
+    def init_f(self):
+        def f(x, a, b):
+            f.count += 1
+            return (x - a)**2 + b
+        f.count = 0
+        return f
+
+    def assert_valid_bracket(self, result, xp):
+        assert xp.all(
+            (result.xl < result.xm) & (result.xm < result.xr)
+        )
+        assert xp.all(
+            (result.fl >= result.fm) & (result.fr > result.fm)
+            | (result.fl > result.fm) & (result.fr > result.fm)
+        )
+
+    def get_kwargs(
+            self, *, xl0=None, xr0=None, factor=None, xmin=None, xmax=None, args=None
+    ):
+        names = ("xl0", "xr0", "xmin", "xmax", "factor", "args")
+        return {
+            name: val for name, val in zip(names, (xl0, xr0, xmin, xmax, factor, args))
+            if val is not None
+        }
+
+    @pytest.mark.parametrize(
+        "seed",
+        (
+            307448016549685229886351382450158984917,
+            11650702770735516532954347931959000479,
+            113767103358505514764278732330028568336,
+        )
+    )
+    @pytest.mark.parametrize("use_xmin", (False, True))
+    @pytest.mark.parametrize("other_side", (False, True))
+    def test_nfev_expected(self, seed, use_xmin, other_side, xp):
+        rng = np.random.default_rng(seed)
+        args = (xp.asarray(0.), xp.asarray(0.))  # f(x) = x^2 with minimum at 0
+        # xl0, xm0, xr0 are chosen such that the initial bracket is to
+        # the right of the minimum, and the bracket will expand
+        # downhill towards zero.
+        xl0, d1, d2, factor = xp.asarray(rng.random(size=4) * [1e5, 10, 10, 5])
+        xm0 = xl0 + d1
+        xr0 = xm0 + d2
+        # Factor should be greater than one.
+        factor += 1
+
+        if use_xmin:
+            xmin = xp.asarray(-rng.random() * 5, dtype=xp.float64)
+            n = int(xp.ceil(xp.log(-(xl0 - xmin) / xmin) / xp.log(factor)))
+            lower = xmin + (xl0 - xmin)*factor**-n
+            middle = xmin + (xl0 - xmin)*factor**-(n-1)
+            upper = xmin + (xl0 - xmin)*factor**-(n-2) if n > 1 else xm0
+            # It may be the case the lower is below the minimum, but we still
+            # don't have a valid bracket.
+            if middle**2 > lower**2:
+                n += 1
+                lower, middle, upper = (
+                    xmin + (xl0 - xmin)*factor**-n, lower, middle
+                )
+        else:
+            xmin = None
+            n = int(xp.ceil(xp.log(xl0 / d1) / xp.log(factor)))
+            lower = xl0 - d1*factor**n
+            middle = xl0 - d1*factor**(n-1) if n > 1 else xl0
+            upper = xl0 - d1*factor**(n-2) if n > 1 else xm0
+            # It may be the case the lower is below the minimum, but we still
+            # don't have a valid bracket.
+            if middle**2 > lower**2:
+                n += 1
+                lower, middle, upper = (
+                    xl0 - d1*factor**n, lower, middle
+                )
+        f = self.init_f()
+
+        xmax = None
+        if other_side:
+            xl0, xm0, xr0 = -xr0, -xm0, -xl0
+            xmin, xmax = None, -xmin if xmin is not None else None
+            lower, middle, upper = -upper, -middle, -lower
+
+        kwargs = self.get_kwargs(
+            xl0=xl0, xr0=xr0, xmin=xmin, xmax=xmax, factor=factor, args=args
+        )
+        result = _bracket_minimum(f, xp.asarray(xm0), **kwargs)
+
+        # Check that `nfev` and `nit` have the correct relationship
+        assert result.nfev == result.nit + 3
+        # Check that `nfev` reports the correct number of function evaluations.
+        assert result.nfev == f.count
+        # Check that the number of iterations matches the theoretical value.
+        assert result.nit == n
+
+        # Compare reported bracket to theoretical bracket and reported function
+        # values to function evaluated at bracket.
+        xp_assert_close(result.xl, lower)
+        xp_assert_close(result.xm, middle)
+        xp_assert_close(result.xr, upper)
+        xp_assert_close(result.fl, f(lower, *args))
+        xp_assert_close(result.fm, f(middle, *args))
+        xp_assert_close(result.fr, f(upper, *args))
+
+        self.assert_valid_bracket(result, xp)
+        assert result.status == 0
+        assert result.success
+
+    def test_flags(self, xp):
+        # Test cases that should produce different status flags; show that all
+        # can be produced simultaneously
+        def f(xs, js):
+            funcs = [lambda x: (x - 1.5)**2,
+                     lambda x: x,
+                     lambda x: x,
+                     lambda x: xp.asarray(xp.nan),
+                     lambda x: x**2]
+
+            return [funcs[int(j)](x) for x, j in zip(xs, js)]
+
+        args = (xp.arange(5, dtype=xp.int64),)
+        xl0 = xp.asarray([-1.0, -1.0, -1.0, -1.0, 6.0])
+        xm0 = xp.asarray([0.0, 0.0, 0.0, 0.0, 4.0])
+        xr0 = xp.asarray([1.0, 1.0, 1.0, 1.0, 2.0])
+        xmin = xp.asarray([-xp.inf, -1.0, -xp.inf, -xp.inf, 8.0])
+
+        result = _bracket_minimum(f, xm0, xl0=xl0, xr0=xr0, xmin=xmin,
+                                  args=args, maxiter=3)
+
+        reference_flags = xp.asarray([eim._ECONVERGED, _ELIMITS,
+                                      eim._ECONVERR, eim._EVALUEERR,
+                                      eim._EINPUTERR], dtype=xp.int32)
+        xp_assert_equal(result.status, reference_flags)
+
+    @pytest.mark.parametrize("minimum", (0.622, [0.622, 0.623]))
+    @pytest.mark.parametrize("dtype", ("float16", "float32", "float64"))
+    @pytest.mark.parametrize("xmin", [-5, None])
+    @pytest.mark.parametrize("xmax", [5, None])
+    def test_dtypes(self, minimum, xmin, xmax, dtype, xp):
+        dtype = getattr(xp, dtype)
+        xmin = xmin if xmin is None else xp.asarray(xmin, dtype=dtype)
+        xmax = xmax if xmax is None else xp.asarray(xmax, dtype=dtype)
+        minimum = xp.asarray(minimum, dtype=dtype)
+
+        def f(x, minimum):
+            return xp.astype((x - minimum)**2, dtype)
+
+        xl0, xm0, xr0 = [-0.01, 0.0, 0.01]
+        result = _bracket_minimum(
+            f, xp.asarray(xm0, dtype=dtype), xl0=xp.asarray(xl0, dtype=dtype),
+            xr0=xp.asarray(xr0, dtype=dtype), xmin=xmin, xmax=xmax, args=(minimum, )
+        )
+        assert xp.all(result.success)
+        assert result.xl.dtype == result.xm.dtype == result.xr.dtype == dtype
+        assert result.fl.dtype == result.fm.dtype == result.fr.dtype == dtype
+
+    @pytest.mark.skip_xp_backends(np_only=True, reason="str/object arrays")
+    def test_input_validation(self, xp):
+        # Test input validation for appropriate error messages
+
+        message = '`func` must be callable.'
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(None, -4, xl0=4)
+
+        message = '...must be numeric and real.'
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(4+1j))
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(-4), xl0=4+1j)
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(-4), xr0=4+1j)
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(-4), xmin=4+1j)
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(-4), xmax=4+1j)
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(-4), factor=4+1j)
+
+        message = "All elements of `factor` must be greater than 1."
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x, xp.asarray(-4), factor=0.5)
+
+        message = "Array shapes are incompatible for broadcasting."
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray([-2, -3]), xl0=[-3, -4, -5])
+
+        message = '`maxiter` must be a non-negative integer.'
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(-4), xr0=4, maxiter=1.5)
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(-4), xr0=4, maxiter=-1)
+        with pytest.raises(ValueError, match=message):
+            _bracket_minimum(lambda x: x**2, xp.asarray(-4), xr0=4, maxiter="ekki")
+
+    @pytest.mark.parametrize("xl0", [0.0, None])
+    @pytest.mark.parametrize("xm0", (0.05, 0.1, 0.15))
+    @pytest.mark.parametrize("xr0", (0.2, 0.4, 0.6, None))
+    # Minimum is ``a`` for each tuple ``(a, b)`` below. Tests cases where minimum
+    # is within, or at varying distances to the left or right of the initial
+    # bracket.
+    @pytest.mark.parametrize(
+        "args",
+        (
+            (1.2, 0), (-0.5, 0), (0.1, 0), (0.2, 0), (3.6, 0), (21.4, 0),
+            (121.6, 0), (5764.1, 0), (-6.4, 0), (-12.9, 0), (-146.2, 0)
+        )
+    )
+    def test_scalar_no_limits(self, xl0, xm0, xr0, args, xp):
+        f = self.init_f()
+        kwargs = self.get_kwargs(xl0=xl0, xr0=xr0, args=tuple(map(xp.asarray, args)))
+        result = _bracket_minimum(f, xp.asarray(xm0, dtype=xp.float64), **kwargs)
+        self.assert_valid_bracket(result, xp)
+        assert result.status == 0
+        assert result.success
+        assert result.nfev == f.count
+
+    @pytest.mark.parametrize(
+        # xmin is set at 0.0 in all cases.
+        "xl0,xm0,xr0,xmin",
+        (
+            # Initial bracket at varying distances from the xmin.
+            (0.5, 0.75, 1.0, 0.0),
+            (1.0, 2.5, 4.0, 0.0),
+            (2.0, 4.0, 6.0, 0.0),
+            (12.0, 16.0, 20.0, 0.0),
+            # Test default initial left endpoint selection. It should not
+            # be below xmin.
+            (None, 0.75, 1.0, 0.0),
+            (None, 2.5, 4.0, 0.0),
+            (None, 4.0, 6.0, 0.0),
+            (None, 16.0, 20.0, 0.0),
+        )
+    )
+    @pytest.mark.parametrize(
+        "args", (
+            (0.0, 0.0), # Minimum is directly at xmin.
+            (1e-300, 0.0), # Minimum is extremely close to xmin.
+            (1e-20, 0.0), # Minimum is very close to xmin.
+            # Minimum at varying distances from xmin.
+            (0.1, 0.0),
+            (0.2, 0.0),
+            (0.4, 0.0)
+        )
+    )
+    def test_scalar_with_limit_left(self, xl0, xm0, xr0, xmin, args, xp):
+        f = self.init_f()
+        kwargs = self.get_kwargs(xl0=xl0, xr0=xr0, xmin=xmin,
+                                 args=tuple(map(xp.asarray, args)))
+        result = _bracket_minimum(f, xp.asarray(xm0), **kwargs)
+        self.assert_valid_bracket(result, xp)
+        assert result.status == 0
+        assert result.success
+        assert result.nfev == f.count
+
+    @pytest.mark.parametrize(
+        #xmax is set to 1.0 in all cases.
+        "xl0,xm0,xr0,xmax",
+        (
+            # Bracket at varying distances from xmax.
+            (0.2, 0.3, 0.4, 1.0),
+            (0.05, 0.075, 0.1, 1.0),
+            (-0.2, -0.1, 0.0, 1.0),
+            (-21.2, -17.7, -14.2, 1.0),
+            # Test default right endpoint selection. It should not exceed xmax.
+            (0.2, 0.3, None, 1.0),
+            (0.05, 0.075, None, 1.0),
+            (-0.2, -0.1, None, 1.0),
+            (-21.2, -17.7, None, 1.0),
+        )
+    )
+    @pytest.mark.parametrize(
+        "args", (
+            (0.9999999999999999, 0.0), # Minimum very close to xmax.
+            # Minimum at varying distances from xmax.
+            (0.9, 0.0),
+            (0.7, 0.0),
+            (0.5, 0.0)
+        )
+    )
+    def test_scalar_with_limit_right(self, xl0, xm0, xr0, xmax, args, xp):
+        f = self.init_f()
+        args = tuple(xp.asarray(arg, dtype=xp.float64) for arg in args)
+        kwargs = self.get_kwargs(xl0=xl0, xr0=xr0, xmax=xmax, args=args)
+        result = _bracket_minimum(f, xp.asarray(xm0, dtype=xp.float64), **kwargs)
+        self.assert_valid_bracket(result, xp)
+        assert result.status == 0
+        assert result.success
+        assert result.nfev == f.count
+
+    @pytest.mark.parametrize(
+        "xl0,xm0,xr0,xmin,xmax,args",
+        (
+            (   # Case 1:
+                # Initial bracket.
+                0.2,
+                0.3,
+                0.4,
+                # Function slopes down to the right from the bracket to a minimum
+                # at 1.0. xmax is also at 1.0
+                None,
+                1.0,
+                (1.0, 0.0)
+            ),
+            (   # Case 2:
+                # Initial bracket.
+                1.4,
+                1.95,
+                2.5,
+                # Function slopes down to the left from the bracket to a minimum at
+                # 0.3 with xmin set to 0.3.
+                0.3,
+                None,
+                (0.3, 0.0)
+            ),
+            (
+                # Case 3:
+                # Initial bracket.
+                2.6,
+                3.25,
+                3.9,
+                # Function slopes down and to the right to a minimum at 99.4 with xmax
+                # at 99.4. Tests case where minimum is at xmax relatively further from
+                # the bracket.
+                None,
+                99.4,
+                (99.4, 0)
+            ),
+            (
+                # Case 4:
+                # Initial bracket.
+                4,
+                4.5,
+                5,
+                # Function slopes down and to the left away from the bracket with a
+                # minimum at -26.3 with xmin set to -26.3. Tests case where minimum is
+                # at xmin relatively far from the bracket.
+                -26.3,
+                None,
+                (-26.3, 0)
+            ),
+            (
+                # Case 5:
+                # Similar to Case 1 above, but tests default values of xl0 and xr0.
+                None,
+                0.3,
+                None,
+                None,
+                1.0,
+                (1.0, 0.0)
+            ),
+            (   # Case 6:
+                # Similar to Case 2 above, but tests default values of xl0 and xr0.
+                None,
+                1.95,
+                None,
+                0.3,
+                None,
+                (0.3, 0.0)
+            ),
+            (
+                # Case 7:
+                # Similar to Case 3 above, but tests default values of xl0 and xr0.
+                None,
+                3.25,
+                None,
+                None,
+                99.4,
+                (99.4, 0)
+            ),
+            (
+                # Case 8:
+                # Similar to Case 4 above, but tests default values of xl0 and xr0.
+                None,
+                4.5,
+                None,
+                -26.3,
+                None,
+                (-26.3, 0)
+            ),
+        )
+    )
+    def test_minimum_at_boundary_point(self, xl0, xm0, xr0, xmin, xmax, args, xp):
+        f = self.init_f()
+        kwargs = self.get_kwargs(xr0=xr0, xmin=xmin, xmax=xmax,
+                                 args=tuple(map(xp.asarray, args)))
+        result = _bracket_minimum(f, xp.asarray(xm0), **kwargs)
+        assert result.status == -1
+        assert args[0] in (result.xl, result.xr)
+        assert result.nfev == f.count
+
+    @pytest.mark.parametrize('shape', [tuple(), (12, ), (3, 4), (3, 2, 2)])
+    def test_vectorization(self, shape, xp):
+        # Test for correct functionality, output shapes, and dtypes for
+        # various input shapes.
+        a = np.linspace(-0.05, 1.05, 12).reshape(shape) if shape else 0.6
+        args = (a, 0.)
+        maxiter = 10
+
+        @np.vectorize
+        def bracket_minimum_single(xm0, xl0, xr0, xmin, xmax, factor, a):
+            return _bracket_minimum(self.init_f(), xm0, xl0=xl0, xr0=xr0, xmin=xmin,
+                                    xmax=xmax, factor=factor, maxiter=maxiter,
+                                    args=(a, 0.0))
+
+        f = self.init_f()
+
+        rng = np.random.default_rng(2348234)
+        xl0 = -rng.random(size=shape)
+        xr0 = rng.random(size=shape)
+        xm0 = xl0 + rng.random(size=shape) * (xr0 - xl0)
+        xmin, xmax = 1e3*xl0, 1e3*xr0
+        if shape:  # make some elements un
+            i = rng.random(size=shape) > 0.5
+            xmin[i], xmax[i] = -np.inf, np.inf
+        factor = rng.random(size=shape) + 1.5
+        refs = bracket_minimum_single(xm0, xl0, xr0, xmin, xmax, factor, a).ravel()
+        args = tuple(xp.asarray(arg, dtype=xp.float64) for arg in args)
+        res = _bracket_minimum(f, xp.asarray(xm0), xl0=xp.asarray(xl0),
+                               xr0=xp.asarray(xr0), xmin=xp.asarray(xmin),
+                               xmax=xp.asarray(xmax), factor=xp.asarray(factor),
+                               args=args, maxiter=maxiter)
+
+        attrs = ['xl', 'xm', 'xr', 'fl', 'fm', 'fr', 'success', 'nfev', 'nit']
+        for attr in attrs:
+            ref_attr = [xp.asarray(getattr(ref, attr)) for ref in refs]
+            res_attr = getattr(res, attr)
+            xp_assert_close(xp_ravel(res_attr, xp=xp), xp.stack(ref_attr))
+            assert res_attr.shape == shape
+
+        assert res.success.dtype == xp.bool
+        if shape:
+            assert xp.all(res.success[1:-1])
+        assert res.status.dtype == xp.int32
+        assert res.nfev.dtype == xp.int32
+        assert res.nit.dtype == xp.int32
+        assert xp.max(res.nit) == f.count - 3
+        self.assert_valid_bracket(res, xp)
+        xp_assert_close(res.fl, f(res.xl, *args))
+        xp_assert_close(res.fm, f(res.xm, *args))
+        xp_assert_close(res.fr, f(res.xr, *args))
+
+    def test_special_cases(self, xp):
+        # Test edge cases and other special cases.
+
+        # Test that integers are not passed to `f`
+        # (otherwise this would overflow)
+        def f(x):
+            assert xp.isdtype(x.dtype, "numeric")
+            return x ** 98 - 1
+
+        result = _bracket_minimum(f, xp.asarray(-7., dtype=xp.float64), xr0=5)
+        assert result.success
+
+        # Test maxiter = 0. Should do nothing to bracket.
+        def f(x):
+            return x**2 - 10
+
+        xl0, xm0, xr0 = xp.asarray(-3.), xp.asarray(-1.), xp.asarray(2.)
+        result = _bracket_minimum(f, xm0, xl0=xl0, xr0=xr0, maxiter=0)
+        xp_assert_equal(result.xl, xl0)
+        xp_assert_equal(result.xm, xm0)
+        xp_assert_equal(result.xr, xr0)
+
+        # Test scalar `args` (not in tuple)
+        def f(x, c):
+            return c*x**2 - 1
+
+        result = _bracket_minimum(f, xp.asarray(-1.), args=xp.asarray(3.))
+        assert result.success
+        xp_assert_close(result.fl, f(result.xl, 3))
+
+        # Initial bracket is valid.
+        f = self.init_f()
+        xl0, xm0, xr0 = xp.asarray(-1.0), xp.asarray(-0.2), xp.asarray(1.0)
+        args = (xp.asarray(0.), xp.asarray(0.))
+        result = _bracket_minimum(f, xm0, xl0=xl0, xr0=xr0, args=args)
+        assert f.count == 3
+
+        xp_assert_equal(result.xl, xl0)
+        xp_assert_equal(result.xm , xm0)
+        xp_assert_equal(result.xr, xr0)
+        xp_assert_equal(result.fl, f(xl0, *args))
+        xp_assert_equal(result.fm, f(xm0, *args))
+        xp_assert_equal(result.fr, f(xr0, *args))
+
+    def test_gh_20562_left(self, xp):
+        # Regression test for https://github.com/scipy/scipy/issues/20562
+        # minimum of f in [xmin, xmax] is at xmin.
+        xmin, xmax = xp.asarray(0.21933608), xp.asarray(1.39713606)
+
+        def f(x):
+            log_a, log_b = xp.log(xmin), xp.log(xmax)
+            return -((log_b - log_a)*x)**-1
+
+        result = _bracket_minimum(f, xp.asarray(0.5535723499480897), xmin=xmin,
+                                  xmax=xmax)
+        xp_assert_close(result.xl, xmin)
+
+    def test_gh_20562_right(self, xp):
+        # Regression test for https://github.com/scipy/scipy/issues/20562
+        # minimum of f in [xmin, xmax] is at xmax.
+        xmin, xmax = xp.asarray(-1.39713606), xp.asarray(-0.21933608)
+
+        def f(x):
+            log_a, log_b = xp.log(-xmax), xp.log(-xmin)
+            return ((log_b - log_a)*x)**-1
+
+        result = _bracket_minimum(f, xp.asarray(-0.5535723499480897),
+                                  xmin=xmin, xmax=xmax)
+        xp_assert_close(result.xr, xmax)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_chandrupatla.py

@@ -0,0 +1,982 @@
+import math
+import pytest
+import numpy as np
+from copy import deepcopy
+
+from scipy import stats, special
+import scipy._lib._elementwise_iterative_method as eim
+import scipy._lib.array_api_extra as xpx
+from scipy._lib._array_api import array_namespace, is_cupy, is_numpy, xp_ravel, xp_size
+from scipy._lib._array_api_no_0d import (xp_assert_close, xp_assert_equal,
+                                         xp_assert_less)
+
+from scipy.optimize.elementwise import find_minimum, find_root
+from scipy.optimize._tstutils import _CHANDRUPATLA_TESTS
+
+from itertools import permutations
+
+
+def _vectorize(xp):
+    # xp-compatible version of np.vectorize
+    # assumes arguments are all arrays of the same shape
+    def decorator(f):
+        def wrapped(*arg_arrays):
+            shape = arg_arrays[0].shape
+            arg_arrays = [xp_ravel(arg_array, xp=xp) for arg_array in arg_arrays]
+            res = []
+            for i in range(math.prod(shape)):
+                arg_scalars = [arg_array[i] for arg_array in arg_arrays]
+                res.append(f(*arg_scalars))
+            return res
+
+        return wrapped
+
+    return decorator
+
+
+# These tests were originally written for the private `optimize._chandrupatla`
+# interfaces, but now we want the tests to check the behavior of the public
+# `optimize.elementwise` interfaces. Therefore, rather than importing
+# `_chandrupatla`/`_chandrupatla_minimize` from `_chandrupatla.py`, we import
+# `find_root`/`find_minimum` from `optimize.elementwise` and wrap those
+# functions to conform to the private interface. This may look a little strange,
+# since it effectively just inverts the interface transformation done within the
+# `find_root`/`find_minimum` functions, but it allows us to run the original,
+# unmodified tests on the public interfaces, simplifying the PR that adds
+# the public interfaces. We'll refactor this when we want to @parametrize the
+# tests over multiple `method`s.
+def _wrap_chandrupatla(func):
+    def _chandrupatla_wrapper(f, *bracket, **kwargs):
+        # avoid passing arguments to `find_minimum` to this function
+        tol_keys = {'xatol', 'xrtol', 'fatol', 'frtol'}
+        tolerances = {key: kwargs.pop(key) for key in tol_keys if key in kwargs}
+        _callback = kwargs.pop('callback', None)
+        if callable(_callback):
+            def callback(res):
+                if func == find_root:
+                    res.xl, res.xr = res.bracket
+                    res.fl, res.fr = res.f_bracket
+                else:
+                    res.xl, res.xm, res.xr = res.bracket
+                    res.fl, res.fm, res.fr = res.f_bracket
+                res.fun = res.f_x
+                del res.bracket
+                del res.f_bracket
+                del res.f_x
+                return _callback(res)
+        else:
+            callback = _callback
+
+        res = func(f, bracket, tolerances=tolerances, callback=callback, **kwargs)
+        if func == find_root:
+            res.xl, res.xr = res.bracket
+            res.fl, res.fr = res.f_bracket
+        else:
+            res.xl, res.xm, res.xr = res.bracket
+            res.fl, res.fm, res.fr = res.f_bracket
+        res.fun = res.f_x
+        del res.bracket
+        del res.f_bracket
+        del res.f_x
+        return res
+    return _chandrupatla_wrapper
+
+
+_chandrupatla_minimize = _wrap_chandrupatla(find_minimum)
+
+
+def f1(x):
+    return 100*(1 - x**3.)**2 + (1-x**2.) + 2*(1-x)**2.
+
+
+def f2(x):
+    return 5 + (x - 2.)**6
+
+
+def f3(x):
+    xp = array_namespace(x)
+    return xp.exp(x) - 5*x
+
+
+def f4(x):
+    return x**5. - 5*x**3. - 20.*x + 5.
+
+
+def f5(x):
+    return 8*x**3 - 2*x**2 - 7*x + 3
+
+
+def _bracket_minimum(func, x1, x2):
+    phi = 1.61803398875
+    maxiter = 100
+    f1 = func(x1)
+    f2 = func(x2)
+    step = x2 - x1
+    x1, x2, f1, f2, step = ((x2, x1, f2, f1, -step) if f2 > f1
+                            else (x1, x2, f1, f2, step))
+
+    for i in range(maxiter):
+        step *= phi
+        x3 = x2 + step
+        f3 = func(x3)
+        if f3 < f2:
+            x1, x2, f1, f2 = x2, x3, f2, f3
+        else:
+            break
+    return x1, x2, x3, f1, f2, f3
+
+
+cases = [
+    (f1, -1, 11),
+    (f1, -2, 13),
+    (f1, -4, 13),
+    (f1, -8, 15),
+    (f1, -16, 16),
+    (f1, -32, 19),
+    (f1, -64, 20),
+    (f1, -128, 21),
+    (f1, -256, 21),
+    (f1, -512, 19),
+    (f1, -1024, 24),
+    (f2, -1, 8),
+    (f2, -2, 6),
+    (f2, -4, 6),
+    (f2, -8, 7),
+    (f2, -16, 8),
+    (f2, -32, 8),
+    (f2, -64, 9),
+    (f2, -128, 11),
+    (f2, -256, 13),
+    (f2, -512, 12),
+    (f2, -1024, 13),
+    (f3, -1, 11),
+    (f3, -2, 11),
+    (f3, -4, 11),
+    (f3, -8, 10),
+    (f3, -16, 14),
+    (f3, -32, 12),
+    (f3, -64, 15),
+    (f3, -128, 18),
+    (f3, -256, 18),
+    (f3, -512, 19),
+    (f3, -1024, 19),
+    (f4, -0.05, 9),
+    (f4, -0.10, 11),
+    (f4, -0.15, 11),
+    (f4, -0.20, 11),
+    (f4, -0.25, 11),
+    (f4, -0.30, 9),
+    (f4, -0.35, 9),
+    (f4, -0.40, 9),
+    (f4, -0.45, 10),
+    (f4, -0.50, 10),
+    (f4, -0.55, 10),
+    (f5, -0.05, 6),
+    (f5, -0.10, 7),
+    (f5, -0.15, 8),
+    (f5, -0.20, 10),
+    (f5, -0.25, 9),
+    (f5, -0.30, 8),
+    (f5, -0.35, 7),
+    (f5, -0.40, 7),
+    (f5, -0.45, 9),
+    (f5, -0.50, 9),
+    (f5, -0.55, 8)
+]
+
+
+@pytest.mark.skip_xp_backends('dask.array', reason='no take_along_axis')
+@pytest.mark.skip_xp_backends('jax.numpy',
+                              reason='JAX arrays do not support item assignment.')
+@pytest.mark.skip_xp_backends('array_api_strict',
+                              reason='Currently uses fancy indexing assignment.')
+class TestChandrupatlaMinimize:
+
+    def f(self, x, loc):
+        xp = array_namespace(x, loc)
+        res = -xp.exp(-1/2 * (x-loc)**2) / (2*xp.pi)**0.5
+        return xp.asarray(res, dtype=x.dtype)[()]
+
+    @pytest.mark.parametrize('dtype', ('float32', 'float64'))
+    @pytest.mark.parametrize('loc', [0.6, np.linspace(-1.05, 1.05, 10)])
+    def test_basic(self, loc, xp, dtype):
+        # Find mode of normal distribution. Compare mode against location
+        # parameter and value of pdf at mode against expected pdf.
+        rtol = {'float32': 5e-3, 'float64': 5e-7}[dtype]
+        dtype = getattr(xp, dtype)
+        bracket = (xp.asarray(xi, dtype=dtype) for xi in (-5, 0, 5))
+        loc = xp.asarray(loc, dtype=dtype)
+        fun = xp.broadcast_to(xp.asarray(-stats.norm.pdf(0), dtype=dtype), loc.shape)
+
+        res = _chandrupatla_minimize(self.f, *bracket, args=(loc,))
+        xp_assert_close(res.x, loc, rtol=rtol)
+        xp_assert_equal(res.fun, fun)
+
+    @pytest.mark.parametrize('shape', [tuple(), (12,), (3, 4), (3, 2, 2)])
+    def test_vectorization(self, shape, xp):
+        # Test for correct functionality, output shapes, and dtypes for various
+        # input shapes.
+        loc = xp.linspace(-0.05, 1.05, 12).reshape(shape) if shape else xp.asarray(0.6)
+        args = (loc,)
+        bracket = xp.asarray(-5.), xp.asarray(0.), xp.asarray(5.)
+
+        @_vectorize(xp)
+        def chandrupatla_single(loc_single):
+            return _chandrupatla_minimize(self.f, *bracket, args=(loc_single,))
+
+        def f(*args, **kwargs):
+            f.f_evals += 1
+            return self.f(*args, **kwargs)
+        f.f_evals = 0
+
+        res = _chandrupatla_minimize(f, *bracket, args=args)
+        refs = chandrupatla_single(loc)
+
+        attrs = ['x', 'fun', 'success', 'status', 'nfev', 'nit',
+                 'xl', 'xm', 'xr', 'fl', 'fm', 'fr']
+        for attr in attrs:
+            ref_attr = xp.stack([getattr(ref, attr) for ref in refs])
+            res_attr = xp_ravel(getattr(res, attr))
+            xp_assert_equal(res_attr, ref_attr)
+            assert getattr(res, attr).shape == shape
+
+        xp_assert_equal(res.fun, self.f(res.x, *args))
+        xp_assert_equal(res.fl, self.f(res.xl, *args))
+        xp_assert_equal(res.fm, self.f(res.xm, *args))
+        xp_assert_equal(res.fr, self.f(res.xr, *args))
+        assert xp.max(res.nfev) == f.f_evals
+        assert xp.max(res.nit) == f.f_evals - 3
+
+        assert xp.isdtype(res.success.dtype, 'bool')
+        assert xp.isdtype(res.status.dtype, 'integral')
+        assert xp.isdtype(res.nfev.dtype, 'integral')
+        assert xp.isdtype(res.nit.dtype, 'integral')
+
+
+    def test_flags(self, xp):
+        # Test cases that should produce different status flags; show that all
+        # can be produced simultaneously.
+        def f(xs, js):
+            funcs = [lambda x: (x - 2.5) ** 2,
+                     lambda x: x - 10,
+                     lambda x: (x - 2.5) ** 4,
+                     lambda x: xp.full_like(x, xp.asarray(xp.nan))]
+            res = []
+            for i in range(xp_size(js)):
+                x = xs[i, ...]
+                j = int(xp_ravel(js)[i])
+                res.append(funcs[j](x))
+            return xp.stack(res)
+
+        args = (xp.arange(4, dtype=xp.int64),)
+        bracket = (xp.asarray([0]*4, dtype=xp.float64),
+                   xp.asarray([2]*4, dtype=xp.float64),
+                   xp.asarray([np.pi]*4, dtype=xp.float64))
+        res = _chandrupatla_minimize(f, *bracket, args=args, maxiter=10)
+
+        ref_flags = xp.asarray([eim._ECONVERGED, eim._ESIGNERR, eim._ECONVERR,
+                                eim._EVALUEERR], dtype=xp.int32)
+        xp_assert_equal(res.status, ref_flags)
+
+    def test_convergence(self, xp):
+        # Test that the convergence tolerances behave as expected
+        rng = np.random.default_rng(2585255913088665241)
+        p = xp.asarray(rng.random(size=3))
+        bracket = (xp.asarray(-5, dtype=xp.float64), xp.asarray(0), xp.asarray(5))
+        args = (p,)
+        kwargs0 = dict(args=args, xatol=0, xrtol=0, fatol=0, frtol=0)
+
+        kwargs = kwargs0.copy()
+        kwargs['xatol'] = 1e-3
+        res1 = _chandrupatla_minimize(self.f, *bracket, **kwargs)
+        j1 = xp.abs(res1.xr - res1.xl)
+        tol = xp.asarray(4*kwargs['xatol'], dtype=p.dtype)
+        xp_assert_less(j1, xp.full((3,), tol, dtype=p.dtype))
+        kwargs['xatol'] = 1e-6
+        res2 = _chandrupatla_minimize(self.f, *bracket, **kwargs)
+        j2 = xp.abs(res2.xr - res2.xl)
+        tol = xp.asarray(4*kwargs['xatol'], dtype=p.dtype)
+        xp_assert_less(j2, xp.full((3,), tol, dtype=p.dtype))
+        xp_assert_less(j2, j1)
+
+        kwargs = kwargs0.copy()
+        kwargs['xrtol'] = 1e-3
+        res1 = _chandrupatla_minimize(self.f, *bracket, **kwargs)
+        j1 = xp.abs(res1.xr - res1.xl)
+        tol = xp.asarray(4*kwargs['xrtol']*xp.abs(res1.x), dtype=p.dtype)
+        xp_assert_less(j1, tol)
+        kwargs['xrtol'] = 1e-6
+        res2 = _chandrupatla_minimize(self.f, *bracket, **kwargs)
+        j2 = xp.abs(res2.xr - res2.xl)
+        tol = xp.asarray(4*kwargs['xrtol']*xp.abs(res2.x), dtype=p.dtype)
+        xp_assert_less(j2, tol)
+        xp_assert_less(j2, j1)
+
+        kwargs = kwargs0.copy()
+        kwargs['fatol'] = 1e-3
+        res1 = _chandrupatla_minimize(self.f, *bracket, **kwargs)
+        h1 = xp.abs(res1.fl - 2 * res1.fm + res1.fr)
+        tol = xp.asarray(2*kwargs['fatol'], dtype=p.dtype)
+        xp_assert_less(h1, xp.full((3,), tol, dtype=p.dtype))
+        kwargs['fatol'] = 1e-6
+        res2 = _chandrupatla_minimize(self.f, *bracket, **kwargs)
+        h2 = xp.abs(res2.fl - 2 * res2.fm + res2.fr)
+        tol = xp.asarray(2*kwargs['fatol'], dtype=p.dtype)
+        xp_assert_less(h2, xp.full((3,), tol, dtype=p.dtype))
+        xp_assert_less(h2, h1)
+
+        kwargs = kwargs0.copy()
+        kwargs['frtol'] = 1e-3
+        res1 = _chandrupatla_minimize(self.f, *bracket, **kwargs)
+        h1 = xp.abs(res1.fl - 2 * res1.fm + res1.fr)
+        tol = xp.asarray(2*kwargs['frtol']*xp.abs(res1.fun), dtype=p.dtype)
+        xp_assert_less(h1, tol)
+        kwargs['frtol'] = 1e-6
+        res2 = _chandrupatla_minimize(self.f, *bracket, **kwargs)
+        h2 = xp.abs(res2.fl - 2 * res2.fm + res2.fr)
+        tol = xp.asarray(2*kwargs['frtol']*abs(res2.fun), dtype=p.dtype)
+        xp_assert_less(h2, tol)
+        xp_assert_less(h2, h1)
+
+    def test_maxiter_callback(self, xp):
+        # Test behavior of `maxiter` parameter and `callback` interface
+        loc = xp.asarray(0.612814)
+        bracket = (xp.asarray(-5), xp.asarray(0), xp.asarray(5))
+        maxiter = 5
+
+        res = _chandrupatla_minimize(self.f, *bracket, args=(loc,),
+                                     maxiter=maxiter)
+        assert not xp.any(res.success)
+        assert xp.all(res.nfev == maxiter+3)
+        assert xp.all(res.nit == maxiter)
+
+        def callback(res):
+            callback.iter += 1
+            callback.res = res
+            assert hasattr(res, 'x')
+            if callback.iter == 0:
+                # callback is called once with initial bracket
+                assert (res.xl, res.xm, res.xr) == bracket
+            else:
+                changed_xr = (res.xl == callback.xl) & (res.xr != callback.xr)
+                changed_xl = (res.xl != callback.xl) & (res.xr == callback.xr)
+                assert xp.all(changed_xr | changed_xl)
+
+            callback.xl = res.xl
+            callback.xr = res.xr
+            assert res.status == eim._EINPROGRESS
+            xp_assert_equal(self.f(res.xl, loc), res.fl)
+            xp_assert_equal(self.f(res.xm, loc), res.fm)
+            xp_assert_equal(self.f(res.xr, loc), res.fr)
+            xp_assert_equal(self.f(res.x, loc), res.fun)
+            if callback.iter == maxiter:
+                raise StopIteration
+
+        callback.xl = xp.nan
+        callback.xr = xp.nan
+        callback.iter = -1  # callback called once before first iteration
+        callback.res = None
+
+        res2 = _chandrupatla_minimize(self.f, *bracket, args=(loc,),
+                                      callback=callback)
+
+        # terminating with callback is identical to terminating due to maxiter
+        # (except for `status`)
+        for key in res.keys():
+            if key == 'status':
+                assert res[key] == eim._ECONVERR
+                # assert callback.res[key] == eim._EINPROGRESS
+                assert res2[key] == eim._ECALLBACK
+            else:
+                assert res2[key] == callback.res[key] == res[key]
+
+    @pytest.mark.parametrize('case', cases)
+    def test_nit_expected(self, case, xp):
+        # Test that `_chandrupatla` implements Chandrupatla's algorithm:
+        # in all 55 test cases, the number of iterations performed
+        # matches the number reported in the original paper.
+        func, x1, nit = case
+
+        # Find bracket using the algorithm in the paper
+        step = 0.2
+        x2 = x1 + step
+        x1, x2, x3, f1, f2, f3 = _bracket_minimum(func, x1, x2)
+
+        # Use tolerances from original paper
+        xatol = 0.0001
+        fatol = 0.000001
+        xrtol = 1e-16
+        frtol = 1e-16
+
+        bracket = xp.asarray(x1), xp.asarray(x2), xp.asarray(x3, dtype=xp.float64)
+        res = _chandrupatla_minimize(func, *bracket, xatol=xatol,
+                                     fatol=fatol, xrtol=xrtol, frtol=frtol)
+        xp_assert_equal(res.nit, xp.asarray(nit, dtype=xp.int32))
+
+    @pytest.mark.parametrize("loc", (0.65, [0.65, 0.7]))
+    @pytest.mark.parametrize("dtype", ('float16', 'float32', 'float64'))
+    def test_dtype(self, loc, dtype, xp):
+        # Test that dtypes are preserved
+        dtype = getattr(xp, dtype)
+
+        loc = xp.asarray(loc, dtype=dtype)
+        bracket = (xp.asarray(-3, dtype=dtype),
+                   xp.asarray(1, dtype=dtype),
+                   xp.asarray(5, dtype=dtype))
+
+        def f(x, loc):
+            assert x.dtype == dtype
+            return xp.astype((x - loc)**2, dtype)
+
+        res = _chandrupatla_minimize(f, *bracket, args=(loc,))
+        assert res.x.dtype == dtype
+        xp_assert_close(res.x, loc, rtol=math.sqrt(xp.finfo(dtype).eps))
+
+    def test_input_validation(self, xp):
+        # Test input validation for appropriate error messages
+
+        message = '`func` must be callable.'
+        bracket = xp.asarray(-4), xp.asarray(0), xp.asarray(4)
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(None, *bracket)
+
+        message = 'Abscissae and function output must be real numbers.'
+        bracket = xp.asarray(-4 + 1j), xp.asarray(0), xp.asarray(4)
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket)
+
+        message = "...be broadcast..."
+        bracket = xp.asarray([-2, -3]), xp.asarray([0, 0]), xp.asarray([3, 4, 5])
+        # raised by `np.broadcast, but the traceback is readable IMO
+        with pytest.raises((ValueError, RuntimeError), match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket)
+
+        message = "The shape of the array returned by `func` must be the same"
+        bracket = xp.asarray([-3, -3]), xp.asarray([0, 0]), xp.asarray([5, 5])
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: [x[0, ...], x[1, ...], x[1, ...]],
+                                   *bracket)
+
+        message = 'Tolerances must be non-negative scalars.'
+        bracket = xp.asarray(-4), xp.asarray(0), xp.asarray(4)
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket, xatol=-1)
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket, xrtol=xp.nan)
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket, fatol='ekki')
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket, frtol=xp.nan)
+
+        message = '`maxiter` must be a non-negative integer.'
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket, maxiter=1.5)
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket, maxiter=-1)
+
+        message = '`callback` must be callable.'
+        with pytest.raises(ValueError, match=message):
+            _chandrupatla_minimize(lambda x: x, *bracket, callback='shrubbery')
+
+    def test_bracket_order(self, xp):
+        # Confirm that order of points in bracket doesn't
+        loc = xp.linspace(-1, 1, 6)[:, xp.newaxis]
+        brackets = xp.asarray(list(permutations([-5, 0, 5]))).T
+        res = _chandrupatla_minimize(self.f, *brackets, args=(loc,))
+        assert xp.all(xpx.isclose(res.x, loc) | (res.fun == self.f(loc, loc)))
+        ref = res.x[:, 0]  # all columns should be the same
+        xp_assert_close(*xp.broadcast_arrays(res.x.T, ref), rtol=1e-15)
+
+    def test_special_cases(self, xp):
+        # Test edge cases and other special cases
+
+        # Test that integers are not passed to `f`
+        def f(x):
+            assert xp.isdtype(x.dtype, "real floating")
+            return (x - 1)**2
+
+        bracket = xp.asarray(-7), xp.asarray(0), xp.asarray(8)
+        with np.errstate(invalid='ignore'):
+            res = _chandrupatla_minimize(f, *bracket, fatol=0, frtol=0)
+        assert res.success
+        xp_assert_close(res.x, xp.asarray(1.), rtol=1e-3)
+        xp_assert_close(res.fun, xp.asarray(0.), atol=1e-200)
+
+        # Test that if all elements of bracket equal minimizer, algorithm
+        # reports convergence
+        def f(x):
+            return (x-1)**2
+
+        bracket = xp.asarray(1), xp.asarray(1), xp.asarray(1)
+        res = _chandrupatla_minimize(f, *bracket)
+        assert res.success
+        xp_assert_equal(res.x, xp.asarray(1.))
+
+        # Test maxiter = 0. Should do nothing to bracket.
+        def f(x):
+            return (x-1)**2
+
+        bracket = xp.asarray(-3), xp.asarray(1.1), xp.asarray(5)
+        res = _chandrupatla_minimize(f, *bracket, maxiter=0)
+        assert res.xl, res.xr == bracket
+        assert res.nit == 0
+        assert res.nfev == 3
+        assert res.status == -2
+        assert res.x == 1.1  # best so far
+
+        # Test scalar `args` (not in tuple)
+        def f(x, c):
+            return (x-c)**2 - 1
+
+        bracket = xp.asarray(-1), xp.asarray(0), xp.asarray(1)
+        c = xp.asarray(1/3)
+        res = _chandrupatla_minimize(f, *bracket, args=(c,))
+        xp_assert_close(res.x, c)
+
+        # Test zero tolerances
+        def f(x):
+            return -xp.sin(x)
+
+        bracket = xp.asarray(0), xp.asarray(1), xp.asarray(xp.pi)
+        res = _chandrupatla_minimize(f, *bracket, xatol=0, xrtol=0, fatol=0, frtol=0)
+        assert res.success
+        # found a minimum exactly (according to floating point arithmetic)
+        assert res.xl < res.xm < res.xr
+        assert f(res.xl) == f(res.xm) == f(res.xr)
+
+
+@pytest.mark.skip_xp_backends('dask.array', reason='boolean indexing assignment')
+@pytest.mark.skip_xp_backends('array_api_strict',
+                              reason='Currently uses fancy indexing assignment.')
+@pytest.mark.skip_xp_backends('jax.numpy',
+                              reason='JAX arrays do not support item assignment.')
+class TestFindRoot:
+
+    def f(self, q, p):
+        return special.ndtr(q) - p
+
+    @pytest.mark.parametrize('p', [0.6, np.linspace(-0.05, 1.05, 10)])
+    def test_basic(self, p, xp):
+        # Invert distribution CDF and compare against distribution `ppf`
+        a, b = xp.asarray(-5.), xp.asarray(5.)
+        res = find_root(self.f, (a, b), args=(xp.asarray(p),))
+        ref = xp.asarray(stats.norm().ppf(p), dtype=xp.asarray(p).dtype)
+        xp_assert_close(res.x, ref)
+
+    @pytest.mark.parametrize('shape', [tuple(), (12,), (3, 4), (3, 2, 2)])
+    def test_vectorization(self, shape, xp):
+        # Test for correct functionality, output shapes, and dtypes for various
+        # input shapes.
+        p = (np.linspace(-0.05, 1.05, 12).reshape(shape) if shape
+             else np.float64(0.6))
+        p_xp = xp.asarray(p)
+        args_xp = (p_xp,)
+        dtype = p_xp.dtype
+
+        @np.vectorize
+        def find_root_single(p):
+            return find_root(self.f, (-5, 5), args=(p,))
+
+        def f(*args, **kwargs):
+            f.f_evals += 1
+            return self.f(*args, **kwargs)
+        f.f_evals = 0
+
+        bracket = xp.asarray(-5., dtype=xp.float64), xp.asarray(5., dtype=xp.float64)
+        res = find_root(f, bracket, args=args_xp)
+        refs = find_root_single(p).ravel()
+
+        ref_x = [ref.x for ref in refs]
+        ref_x = xp.reshape(xp.asarray(ref_x, dtype=dtype), shape)
+        xp_assert_close(res.x, ref_x)
+
+        ref_f = [ref.f_x for ref in refs]
+        ref_f = xp.reshape(xp.asarray(ref_f, dtype=dtype), shape)
+        xp_assert_close(res.f_x, ref_f, atol=1e-15)
+        xp_assert_equal(res.f_x, self.f(res.x, *args_xp))
+
+        ref_success = [bool(ref.success) for ref in refs]
+        ref_success = xp.reshape(xp.asarray(ref_success, dtype=xp.bool), shape)
+        xp_assert_equal(res.success, ref_success)
+
+        ref_status = [ref.status for ref in refs]
+        ref_status = xp.reshape(xp.asarray(ref_status, dtype=xp.int32), shape)
+        xp_assert_equal(res.status, ref_status)
+
+        ref_nfev = [ref.nfev for ref in refs]
+        ref_nfev = xp.reshape(xp.asarray(ref_nfev, dtype=xp.int32), shape)
+        if is_numpy(xp):
+            xp_assert_equal(res.nfev, ref_nfev)
+            assert xp.max(res.nfev) == f.f_evals
+        else:  # different backend may lead to different nfev
+            assert res.nfev.shape == shape
+            assert res.nfev.dtype == xp.int32
+
+        ref_nit = [ref.nit for ref in refs]
+        ref_nit = xp.reshape(xp.asarray(ref_nit, dtype=xp.int32), shape)
+        if is_numpy(xp):
+            xp_assert_equal(res.nit, ref_nit)
+            assert xp.max(res.nit) == f.f_evals-2
+        else:
+            assert res.nit.shape == shape
+            assert res.nit.dtype == xp.int32
+
+        ref_xl = [ref.bracket[0] for ref in refs]
+        ref_xl = xp.reshape(xp.asarray(ref_xl, dtype=dtype), shape)
+        xp_assert_close(res.bracket[0], ref_xl)
+
+        ref_xr = [ref.bracket[1] for ref in refs]
+        ref_xr = xp.reshape(xp.asarray(ref_xr, dtype=dtype), shape)
+        xp_assert_close(res.bracket[1], ref_xr)
+
+        xp_assert_less(res.bracket[0], res.bracket[1])
+        finite = xp.isfinite(res.x)
+        assert xp.all((res.x[finite] == res.bracket[0][finite])
+                      | (res.x[finite] == res.bracket[1][finite]))
+
+        # PyTorch and CuPy don't solve to the same accuracy as NumPy - that's OK.
+        atol = 1e-15 if is_numpy(xp) else 1e-9
+
+        ref_fl = [ref.f_bracket[0] for ref in refs]
+        ref_fl = xp.reshape(xp.asarray(ref_fl, dtype=dtype), shape)
+        xp_assert_close(res.f_bracket[0], ref_fl, atol=atol)
+        xp_assert_equal(res.f_bracket[0], self.f(res.bracket[0], *args_xp))
+
+        ref_fr = [ref.f_bracket[1] for ref in refs]
+        ref_fr = xp.reshape(xp.asarray(ref_fr, dtype=dtype), shape)
+        xp_assert_close(res.f_bracket[1], ref_fr, atol=atol)
+        xp_assert_equal(res.f_bracket[1], self.f(res.bracket[1], *args_xp))
+
+        assert xp.all(xp.abs(res.f_x[finite]) ==
+                      xp.minimum(xp.abs(res.f_bracket[0][finite]),
+                                 xp.abs(res.f_bracket[1][finite])))
+
+    def test_flags(self, xp):
+        # Test cases that should produce different status flags; show that all
+        # can be produced simultaneously.
+        def f(xs, js):
+            # Note that full_like and int(j) shouldn't really be required. CuPy
+            # is just really picky here, so I'm making it a special case to
+            # make sure the other backends work when the user is less careful.
+            assert js.dtype == xp.int64
+            if is_cupy(xp):
+                funcs = [lambda x: x - 2.5,
+                         lambda x: x - 10,
+                         lambda x: (x - 0.1)**3,
+                         lambda x: xp.full_like(x, xp.asarray(xp.nan))]
+                return [funcs[int(j)](x) for x, j in zip(xs, js)]
+
+            funcs = [lambda x: x - 2.5,
+                     lambda x: x - 10,
+                     lambda x: (x - 0.1) ** 3,
+                     lambda x: xp.nan]
+            return [funcs[j](x) for x, j in zip(xs, js)]
+
+        args = (xp.arange(4, dtype=xp.int64),)
+        a, b = xp.asarray([0.]*4), xp.asarray([xp.pi]*4)
+        res = find_root(f, (a, b), args=args, maxiter=2)
+
+        ref_flags = xp.asarray([eim._ECONVERGED,
+                                eim._ESIGNERR,
+                                eim._ECONVERR,
+                                eim._EVALUEERR], dtype=xp.int32)
+        xp_assert_equal(res.status, ref_flags)
+
+    def test_convergence(self, xp):
+        # Test that the convergence tolerances behave as expected
+        rng = np.random.default_rng(2585255913088665241)
+        p = xp.asarray(rng.random(size=3))
+        bracket = (-xp.asarray(5.), xp.asarray(5.))
+        args = (p,)
+        kwargs0 = dict(args=args, tolerances=dict(xatol=0, xrtol=0, fatol=0, frtol=0))
+
+        kwargs = deepcopy(kwargs0)
+        kwargs['tolerances']['xatol'] = 1e-3
+        res1 = find_root(self.f, bracket, **kwargs)
+        xp_assert_less(res1.bracket[1] - res1.bracket[0],
+                       xp.full_like(p, xp.asarray(1e-3)))
+        kwargs['tolerances']['xatol'] = 1e-6
+        res2 = find_root(self.f, bracket, **kwargs)
+        xp_assert_less(res2.bracket[1] - res2.bracket[0],
+                       xp.full_like(p, xp.asarray(1e-6)))
+        xp_assert_less(res2.bracket[1] - res2.bracket[0],
+                       res1.bracket[1] - res1.bracket[0])
+
+        kwargs = deepcopy(kwargs0)
+        kwargs['tolerances']['xrtol'] = 1e-3
+        res1 = find_root(self.f, bracket, **kwargs)
+        xp_assert_less(res1.bracket[1] - res1.bracket[0], 1e-3 * xp.abs(res1.x))
+        kwargs['tolerances']['xrtol'] = 1e-6
+        res2 = find_root(self.f, bracket, **kwargs)
+        xp_assert_less(res2.bracket[1] - res2.bracket[0],
+                       1e-6 * xp.abs(res2.x))
+        xp_assert_less(res2.bracket[1] - res2.bracket[0],
+                       res1.bracket[1] - res1.bracket[0])
+
+        kwargs = deepcopy(kwargs0)
+        kwargs['tolerances']['fatol'] = 1e-3
+        res1 = find_root(self.f, bracket, **kwargs)
+        xp_assert_less(xp.abs(res1.f_x), xp.full_like(p, xp.asarray(1e-3)))
+        kwargs['tolerances']['fatol'] = 1e-6
+        res2 = find_root(self.f, bracket, **kwargs)
+        xp_assert_less(xp.abs(res2.f_x), xp.full_like(p, xp.asarray(1e-6)))
+        xp_assert_less(xp.abs(res2.f_x), xp.abs(res1.f_x))
+
+        kwargs = deepcopy(kwargs0)
+        kwargs['tolerances']['frtol'] = 1e-3
+        x1, x2 = bracket
+        f0 = xp.minimum(xp.abs(self.f(x1, *args)), xp.abs(self.f(x2, *args)))
+        res1 = find_root(self.f, bracket, **kwargs)
+        xp_assert_less(xp.abs(res1.f_x), 1e-3*f0)
+        kwargs['tolerances']['frtol'] = 1e-6
+        res2 = find_root(self.f, bracket, **kwargs)
+        xp_assert_less(xp.abs(res2.f_x), 1e-6*f0)
+        xp_assert_less(xp.abs(res2.f_x), xp.abs(res1.f_x))
+
+    def test_maxiter_callback(self, xp):
+        # Test behavior of `maxiter` parameter and `callback` interface
+        p = xp.asarray(0.612814)
+        bracket = (xp.asarray(-5.), xp.asarray(5.))
+        maxiter = 5
+
+        def f(q, p):
+            res = special.ndtr(q) - p
+            f.x = q
+            f.f_x = res
+            return res
+        f.x = None
+        f.f_x = None
+
+        res = find_root(f, bracket, args=(p,), maxiter=maxiter)
+        assert not xp.any(res.success)
+        assert xp.all(res.nfev == maxiter+2)
+        assert xp.all(res.nit == maxiter)
+
+        def callback(res):
+            callback.iter += 1
+            callback.res = res
+            assert hasattr(res, 'x')
+            if callback.iter == 0:
+                # callback is called once with initial bracket
+                assert (res.bracket[0], res.bracket[1]) == bracket
+            else:
+                changed = (((res.bracket[0] == callback.bracket[0])
+                            & (res.bracket[1] != callback.bracket[1]))
+                           | ((res.bracket[0] != callback.bracket[0])
+                              & (res.bracket[1] == callback.bracket[1])))
+                assert xp.all(changed)
+
+            callback.bracket[0] = res.bracket[0]
+            callback.bracket[1] = res.bracket[1]
+            assert res.status == eim._EINPROGRESS
+            xp_assert_equal(self.f(res.bracket[0], p), res.f_bracket[0])
+            xp_assert_equal(self.f(res.bracket[1], p), res.f_bracket[1])
+            xp_assert_equal(self.f(res.x, p), res.f_x)
+            if callback.iter == maxiter:
+                raise StopIteration
+        callback.iter = -1  # callback called once before first iteration
+        callback.res = None
+        callback.bracket = [None, None]
+
+        res2 = find_root(f, bracket, args=(p,), callback=callback)
+
+        # terminating with callback is identical to terminating due to maxiter
+        # (except for `status`)
+        for key in res.keys():
+            if key == 'status':
+                xp_assert_equal(res[key], xp.asarray(eim._ECONVERR, dtype=xp.int32))
+                xp_assert_equal(res2[key], xp.asarray(eim._ECALLBACK, dtype=xp.int32))
+            elif key in {'bracket', 'f_bracket'}:
+                xp_assert_equal(res2[key][0], res[key][0])
+                xp_assert_equal(res2[key][1], res[key][1])
+            elif key.startswith('_'):
+                continue
+            else:
+                xp_assert_equal(res2[key], res[key])
+
+    @pytest.mark.parametrize('case', _CHANDRUPATLA_TESTS)
+    def test_nit_expected(self, case, xp):
+        # Test that `_chandrupatla` implements Chandrupatla's algorithm:
+        # in all 40 test cases, the number of iterations performed
+        # matches the number reported in the original paper.
+        f, bracket, root, nfeval, id = case
+        # Chandrupatla's criterion is equivalent to
+        # abs(x2-x1) < 4*abs(xmin)*xrtol + xatol, but we use the more standard
+        # abs(x2-x1) < abs(xmin)*xrtol + xatol. Therefore, set xrtol to 4x
+        # that used by Chandrupatla in tests.
+        bracket = (xp.asarray(bracket[0], dtype=xp.float64),
+                   xp.asarray(bracket[1], dtype=xp.float64))
+        root = xp.asarray(root, dtype=xp.float64)
+
+        res = find_root(f, bracket, tolerances=dict(xrtol=4e-10, xatol=1e-5))
+        xp_assert_close(res.f_x, xp.asarray(f(root), dtype=xp.float64),
+                        rtol=1e-8, atol=2e-3)
+        xp_assert_equal(res.nfev, xp.asarray(nfeval, dtype=xp.int32))
+
+    @pytest.mark.parametrize("root", (0.622, [0.622, 0.623]))
+    @pytest.mark.parametrize("dtype", ('float16', 'float32', 'float64'))
+    def test_dtype(self, root, dtype, xp):
+        # Test that dtypes are preserved
+        not_numpy = not is_numpy(xp)
+        if not_numpy and dtype == 'float16':
+            pytest.skip("`float16` dtype only supported for NumPy arrays.")
+
+        dtype = getattr(xp, dtype, None)
+        if dtype is None:
+            pytest.skip(f"{xp} does not support {dtype}")
+
+        def f(x, root):
+            res = (x - root) ** 3.
+            if is_numpy(xp):  # NumPy does not preserve dtype
+                return xp.asarray(res, dtype=dtype)
+            return res
+
+        a, b = xp.asarray(-3, dtype=dtype), xp.asarray(3, dtype=dtype)
+        root = xp.asarray(root, dtype=dtype)
+        res = find_root(f, (a, b), args=(root,), tolerances={'xatol': 1e-3})
+        try:
+            xp_assert_close(res.x, root, atol=1e-3)
+        except AssertionError:
+            assert res.x.dtype == dtype
+            xp.all(res.f_x == 0)
+
+    def test_input_validation(self, xp):
+        # Test input validation for appropriate error messages
+
+        def func(x):
+            return x
+
+        message = '`func` must be callable.'
+        with pytest.raises(ValueError, match=message):
+            bracket = xp.asarray(-4), xp.asarray(4)
+            find_root(None, bracket)
+
+        message = 'Abscissae and function output must be real numbers.'
+        with pytest.raises(ValueError, match=message):
+            bracket = xp.asarray(-4+1j), xp.asarray(4)
+            find_root(func, bracket)
+
+        # raised by `np.broadcast, but the traceback is readable IMO
+        message = "...not be broadcast..."  # all messages include this part
+        with pytest.raises((ValueError, RuntimeError), match=message):
+            bracket = xp.asarray([-2, -3]), xp.asarray([3, 4, 5])
+            find_root(func, bracket)
+
+        message = "The shape of the array returned by `func`..."
+        with pytest.raises(ValueError, match=message):
+            bracket = xp.asarray([-3, -3]), xp.asarray([5, 5])
+            find_root(lambda x: [x[0], x[1], x[1]], bracket)
+
+        message = 'Tolerances must be non-negative scalars.'
+        bracket = xp.asarray(-4), xp.asarray(4)
+        with pytest.raises(ValueError, match=message):
+            find_root(func, bracket, tolerances=dict(xatol=-1))
+        with pytest.raises(ValueError, match=message):
+            find_root(func, bracket, tolerances=dict(xrtol=xp.nan))
+        with pytest.raises(ValueError, match=message):
+            find_root(func, bracket, tolerances=dict(fatol='ekki'))
+        with pytest.raises(ValueError, match=message):
+            find_root(func, bracket, tolerances=dict(frtol=xp.nan))
+
+        message = '`maxiter` must be a non-negative integer.'
+        with pytest.raises(ValueError, match=message):
+            find_root(func, bracket, maxiter=1.5)
+        with pytest.raises(ValueError, match=message):
+            find_root(func, bracket, maxiter=-1)
+
+        message = '`callback` must be callable.'
+        with pytest.raises(ValueError, match=message):
+            find_root(func, bracket, callback='shrubbery')
+
+    def test_special_cases(self, xp):
+        # Test edge cases and other special cases
+
+        # Test infinite function values
+        def f(x):
+            return 1 / x + 1 - 1 / (-x + 1)
+
+        a, b = xp.asarray([0.1, 0., 0., 0.1]),  xp.asarray([0.9, 1.0, 0.9, 1.0])
+
+        with np.errstate(divide='ignore', invalid='ignore'):
+            res = find_root(f, (a, b))
+
+        assert xp.all(res.success)
+        xp_assert_close(res.x[1:], xp.full((3,), res.x[0]))
+
+        # Test that integers are not passed to `f`
+        # (otherwise this would overflow)
+        def f(x):
+            assert xp.isdtype(x.dtype, "real floating")
+            # this would overflow if x were an xp integer dtype
+            return x ** 31 - 1
+
+        # note that all inputs are integer type; result is automatically default float
+        res = find_root(f, (xp.asarray(-7), xp.asarray(5)))
+        assert res.success
+        xp_assert_close(res.x, xp.asarray(1.))
+
+        # Test that if both ends of bracket equal root, algorithm reports
+        # convergence.
+        def f(x, root):
+            return x**2 - root
+
+        root = xp.asarray([0, 1])
+        res = find_root(f, (xp.asarray(1), xp.asarray(1)), args=(root,))
+        xp_assert_equal(res.success, xp.asarray([False, True]))
+        xp_assert_equal(res.x, xp.asarray([xp.nan, 1.]))
+
+        def f(x):
+            return 1/x
+
+        with np.errstate(invalid='ignore'):
+            inf = xp.asarray(xp.inf)
+            res = find_root(f, (inf, inf))
+        assert res.success
+        xp_assert_equal(res.x, xp.asarray(xp.inf))
+
+        # Test maxiter = 0. Should do nothing to bracket.
+        def f(x):
+            return x**3 - 1
+
+        a, b = xp.asarray(-3.), xp.asarray(5.)
+        res = find_root(f, (a, b), maxiter=0)
+        xp_assert_equal(res.success, xp.asarray(False))
+        xp_assert_equal(res.status, xp.asarray(-2, dtype=xp.int32))
+        xp_assert_equal(res.nit, xp.asarray(0, dtype=xp.int32))
+        xp_assert_equal(res.nfev, xp.asarray(2, dtype=xp.int32))
+        xp_assert_equal(res.bracket[0], a)
+        xp_assert_equal(res.bracket[1], b)
+        # The `x` attribute is the one with the smaller function value
+        xp_assert_equal(res.x, a)
+        # Reverse bracket; check that this is still true
+        res = find_root(f, (-b, -a), maxiter=0)
+        xp_assert_equal(res.x, -a)
+
+        # Test maxiter = 1
+        res = find_root(f, (a, b), maxiter=1)
+        xp_assert_equal(res.success, xp.asarray(True))
+        xp_assert_equal(res.status, xp.asarray(0, dtype=xp.int32))
+        xp_assert_equal(res.nit, xp.asarray(1, dtype=xp.int32))
+        xp_assert_equal(res.nfev, xp.asarray(3, dtype=xp.int32))
+        xp_assert_close(res.x, xp.asarray(1.))
+
+        # Test scalar `args` (not in tuple)
+        def f(x, c):
+            return c*x - 1
+
+        res = find_root(f, (xp.asarray(-1), xp.asarray(1)), args=xp.asarray(3))
+        xp_assert_close(res.x, xp.asarray(1/3))
+
+        # # TODO: Test zero tolerance
+        # # ~~What's going on here - why are iterations repeated?~~
+        # # tl goes to zero when xatol=xrtol=0. When function is nearly linear,
+        # # this causes convergence issues.
+        # def f(x):
+        #     return np.cos(x)
+        #
+        # res = _chandrupatla_root(f, 0, np.pi, xatol=0, xrtol=0)
+        # assert res.nit < 100
+        # xp = np.nextafter(res.x, np.inf)
+        # xm = np.nextafter(res.x, -np.inf)
+        # assert np.abs(res.fun) < np.abs(f(xp))
+        # assert np.abs(res.fun) < np.abs(f(xm))

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_cobyla.py

@@ -0,0 +1,195 @@
+import math
+
+import numpy as np
+from numpy.testing import assert_allclose, assert_array_almost_equal
+
+from scipy.optimize import (
+    fmin_cobyla, minimize, Bounds, NonlinearConstraint, LinearConstraint,
+    OptimizeResult
+)
+
+
+class TestCobyla:
+    def setup_method(self):
+        # The algorithm is very fragile on 32 bit, so unfortunately we need to start
+        # very near the solution in order for the test to pass.
+        self.x0 = [np.sqrt(25 - (2.0/3)**2), 2.0/3 + 1e-4]
+        self.solution = [math.sqrt(25 - (2.0/3)**2), 2.0/3]
+        self.opts = {'disp': 0, 'rhobeg': 1, 'tol': 1e-6,
+                     'maxiter': 100}
+
+    def fun(self, x):
+        return x[0]**2 + abs(x[1])**3
+
+    def con1(self, x):
+        return x[0]**2 + x[1]**2 - 25
+
+    def con2(self, x):
+        return -self.con1(x)
+
+    def test_simple(self):
+        # use disp=True as smoke test for gh-8118
+        x = fmin_cobyla(self.fun, self.x0, [self.con1, self.con2], rhobeg=1,
+                        rhoend=1e-5, maxfun=100, disp=1)
+        assert_allclose(x, self.solution, atol=1e-4)
+
+    def test_minimize_simple(self):
+        class Callback:
+            def __init__(self):
+                self.n_calls = 0
+                self.last_x = None
+
+            def __call__(self, x):
+                self.n_calls += 1
+                self.last_x = x
+
+        class CallbackNewSyntax:
+            def __init__(self):
+                self.n_calls = 0
+
+            def __call__(self, intermediate_result):
+                assert isinstance(intermediate_result, OptimizeResult)
+                self.n_calls += 1
+
+        callback = Callback()
+        callback_new_syntax = CallbackNewSyntax()
+
+        # Minimize with method='COBYLA'
+        cons = (NonlinearConstraint(self.con1, 0, np.inf),
+                {'type': 'ineq', 'fun': self.con2})
+        sol = minimize(self.fun, self.x0, method='cobyla', constraints=cons,
+                       callback=callback, options=self.opts)
+        sol_new = minimize(self.fun, self.x0, method='cobyla', constraints=cons,
+                       callback=callback_new_syntax, options=self.opts)
+        assert_allclose(sol.x, self.solution, atol=1e-4)
+        assert sol.success, sol.message
+        assert sol.maxcv < 1e-5, sol
+        assert sol.nfev < 70, sol
+        assert sol.fun < self.fun(self.solution) + 1e-3, sol
+        assert_array_almost_equal(
+            sol.x,
+            callback.last_x,
+            decimal=5,
+            err_msg="Last design vector sent to the callback is not equal to"
+                 " returned value.",
+        )
+        assert sol_new.success, sol_new.message
+        assert sol.fun == sol_new.fun
+        assert sol.maxcv == sol_new.maxcv
+        assert sol.nfev == sol_new.nfev
+        assert callback.n_calls == callback_new_syntax.n_calls, \
+            "Callback is not called the same amount of times for old and new syntax."
+
+    def test_minimize_constraint_violation(self):
+        # We set up conflicting constraints so that the algorithm will be
+        # guaranteed to end up with maxcv > 0.
+        cons = ({'type': 'ineq', 'fun': lambda x: 4 - x},
+                {'type': 'ineq', 'fun': lambda x: x - 5})
+        sol = minimize(lambda x: x, [0], method='cobyla', constraints=cons,
+                       options={'catol': 0.6})
+        assert sol.maxcv > 0.1
+        assert sol.success
+        sol = minimize(lambda x: x, [0], method='cobyla', constraints=cons,
+                       options={'catol': 0.4})
+        assert sol.maxcv > 0.1
+        assert not sol.success
+
+    def test_f_target(self):
+        f_target = 250
+        sol = minimize(lambda x: x**2, [500], method='cobyla',
+                       options={'f_target': f_target})
+        assert sol.status == 1
+        assert sol.success
+        assert sol.fun <= f_target
+
+    def test_minimize_linear_constraints(self):
+        constraints = LinearConstraint([1.0, 1.0], 1.0, 1.0)
+        sol = minimize(
+            self.fun,
+            self.x0,
+            method='cobyla',
+            constraints=constraints,
+            options=self.opts,
+        )
+        solution = [(4 - np.sqrt(7)) / 3, (np.sqrt(7) - 1) / 3]
+        assert_allclose(sol.x, solution, atol=1e-4)
+        assert sol.success, sol.message
+        assert sol.maxcv < 1e-8, sol
+        assert sol.nfev <= 100, sol
+        assert sol.fun < self.fun(solution) + 1e-3, sol
+
+
+def test_vector_constraints():
+    # test that fmin_cobyla and minimize can take a combination
+    # of constraints, some returning a number and others an array
+    def fun(x):
+        return (x[0] - 1)**2 + (x[1] - 2.5)**2
+
+    def fmin(x):
+        return fun(x) - 1
+
+    def cons1(x):
+        a = np.array([[1, -2, 2], [-1, -2, 6], [-1, 2, 2]])
+        return np.array([a[i, 0] * x[0] + a[i, 1] * x[1] +
+                         a[i, 2] for i in range(len(a))])
+
+    def cons2(x):
+        return x     # identity, acts as bounds x > 0
+
+    x0 = np.array([2, 0])
+    cons_list = [fun, cons1, cons2]
+
+    xsol = [1.4, 1.7]
+    fsol = 0.8
+
+    # testing fmin_cobyla
+    sol = fmin_cobyla(fun, x0, cons_list, rhoend=1e-5)
+    assert_allclose(sol, xsol, atol=1e-4)
+
+    sol = fmin_cobyla(fun, x0, fmin, rhoend=1e-5)
+    assert_allclose(fun(sol), 1, atol=1e-4)
+
+    # testing minimize
+    constraints = [{'type': 'ineq', 'fun': cons} for cons in cons_list]
+    sol = minimize(fun, x0, constraints=constraints, tol=1e-5)
+    assert_allclose(sol.x, xsol, atol=1e-4)
+    assert sol.success, sol.message
+    assert_allclose(sol.fun, fsol, atol=1e-4)
+
+    constraints = {'type': 'ineq', 'fun': fmin}
+    sol = minimize(fun, x0, constraints=constraints, tol=1e-5)
+    assert_allclose(sol.fun, 1, atol=1e-4)
+
+
+class TestBounds:
+    # Test cobyla support for bounds (only when used via `minimize`)
+    # Invalid bounds is tested in
+    # test_optimize.TestOptimizeSimple.test_minimize_invalid_bounds
+
+    def test_basic(self):
+        def f(x):
+            return np.sum(x**2)
+
+        lb = [-1, None, 1, None, -0.5]
+        ub = [-0.5, -0.5, None, None, -0.5]
+        bounds = [(a, b) for a, b in zip(lb, ub)]
+        # these are converted to Bounds internally
+
+        res = minimize(f, x0=[1, 2, 3, 4, 5], method='cobyla', bounds=bounds)
+        ref = [-0.5, -0.5, 1, 0, -0.5]
+        assert res.success
+        assert_allclose(res.x, ref, atol=1e-3)
+
+    def test_unbounded(self):
+        def f(x):
+            return np.sum(x**2)
+
+        bounds = Bounds([-np.inf, -np.inf], [np.inf, np.inf])
+        res = minimize(f, x0=[1, 2], method='cobyla', bounds=bounds)
+        assert res.success
+        assert_allclose(res.x, 0, atol=1e-3)
+
+        bounds = Bounds([1, -np.inf], [np.inf, np.inf])
+        res = minimize(f, x0=[1, 2], method='cobyla', bounds=bounds)
+        assert res.success
+        assert_allclose(res.x, [1, 0], atol=1e-3)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_cobyqa.py

@@ -0,0 +1,252 @@
+import numpy as np
+import pytest
+import threading
+from numpy.testing import assert_allclose, assert_equal
+
+from scipy.optimize import (
+    Bounds,
+    LinearConstraint,
+    NonlinearConstraint,
+    OptimizeResult,
+    minimize,
+)
+
+
+class TestCOBYQA:
+
+    def setup_method(self):
+        self.x0 = [4.95, 0.66]
+        self.options = {'maxfev': 100}
+
+    @staticmethod
+    def fun(x, c=1.0):
+        return x[0]**2 + c * abs(x[1])**3
+
+    @staticmethod
+    def con(x):
+        return x[0]**2 + x[1]**2 - 25.0
+
+    def test_minimize_simple(self):
+        class Callback:
+            def __init__(self):
+                self.lock = threading.Lock()
+                self.n_calls = 0
+
+            def __call__(self, x):
+                assert isinstance(x, np.ndarray)
+                with self.lock:
+                    self.n_calls += 1
+
+        class CallbackNewSyntax:
+            def __init__(self):
+                self.lock = threading.Lock()
+                self.n_calls = 0
+
+            def __call__(self, intermediate_result):
+                assert isinstance(intermediate_result, OptimizeResult)
+                with self.lock:
+                    self.n_calls += 1
+
+        x0 = [4.95, 0.66]
+        callback = Callback()
+        callback_new_syntax = CallbackNewSyntax()
+
+        # Minimize with method='cobyqa'.
+        constraints = NonlinearConstraint(self.con, 0.0, 0.0)
+        sol = minimize(
+            self.fun,
+            x0,
+            method='cobyqa',
+            constraints=constraints,
+            callback=callback,
+            options=self.options,
+        )
+        sol_new = minimize(
+            self.fun,
+            x0,
+            method='cobyqa',
+            constraints=constraints,
+            callback=callback_new_syntax,
+            options=self.options,
+        )
+        solution = [np.sqrt(25.0 - 4.0 / 9.0), 2.0 / 3.0]
+        assert_allclose(sol.x, solution, atol=1e-4)
+        assert sol.success, sol.message
+        assert sol.maxcv < 1e-8, sol
+        assert sol.nfev <= 100, sol
+        assert sol.fun < self.fun(solution) + 1e-3, sol
+        assert sol.nfev == callback.n_calls, \
+            "Callback is not called exactly once for every function eval."
+        assert_equal(sol.x, sol_new.x)
+        assert sol_new.success, sol_new.message
+        assert sol.fun == sol_new.fun
+        assert sol.maxcv == sol_new.maxcv
+        assert sol.nfev == sol_new.nfev
+        assert sol.nit == sol_new.nit
+        assert sol_new.nfev == callback_new_syntax.n_calls, \
+            "Callback is not called exactly once for every function eval."
+
+    def test_minimize_bounds(self):
+        def fun_check_bounds(x):
+            assert np.all(bounds.lb <= x) and np.all(x <= bounds.ub)
+            return self.fun(x)
+
+        # Case where the bounds are not active at the solution.
+        bounds = Bounds([4.5, 0.6], [5.0, 0.7])
+        constraints = NonlinearConstraint(self.con, 0.0, 0.0)
+        sol = minimize(
+            fun_check_bounds,
+            self.x0,
+            method='cobyqa',
+            bounds=bounds,
+            constraints=constraints,
+            options=self.options,
+        )
+        solution = [np.sqrt(25.0 - 4.0 / 9.0), 2.0 / 3.0]
+        assert_allclose(sol.x, solution, atol=1e-4)
+        assert sol.success, sol.message
+        assert sol.maxcv < 1e-8, sol
+        assert np.all(bounds.lb <= sol.x) and np.all(sol.x <= bounds.ub), sol
+        assert sol.nfev <= 100, sol
+        assert sol.fun < self.fun(solution) + 1e-3, sol
+
+        # Case where the bounds are active at the solution.
+        bounds = Bounds([5.0, 0.6], [5.5, 0.65])
+        sol = minimize(
+            fun_check_bounds,
+            self.x0,
+            method='cobyqa',
+            bounds=bounds,
+            constraints=constraints,
+            options=self.options,
+        )
+        assert not sol.success, sol.message
+        assert sol.maxcv > 0.35, sol
+        assert np.all(bounds.lb <= sol.x) and np.all(sol.x <= bounds.ub), sol
+        assert sol.nfev <= 100, sol
+
+    def test_minimize_linear_constraints(self):
+        constraints = LinearConstraint([1.0, 1.0], 1.0, 1.0)
+        sol = minimize(
+            self.fun,
+            self.x0,
+            method='cobyqa',
+            constraints=constraints,
+            options=self.options,
+        )
+        solution = [(4 - np.sqrt(7)) / 3, (np.sqrt(7) - 1) / 3]
+        assert_allclose(sol.x, solution, atol=1e-4)
+        assert sol.success, sol.message
+        assert sol.maxcv < 1e-8, sol
+        assert sol.nfev <= 100, sol
+        assert sol.fun < self.fun(solution) + 1e-3, sol
+
+    def test_minimize_args(self):
+        constraints = NonlinearConstraint(self.con, 0.0, 0.0)
+        sol = minimize(
+            self.fun,
+            self.x0,
+            args=(2.0,),
+            method='cobyqa',
+            constraints=constraints,
+            options=self.options,
+        )
+        solution = [np.sqrt(25.0 - 4.0 / 36.0), 2.0 / 6.0]
+        assert_allclose(sol.x, solution, atol=1e-4)
+        assert sol.success, sol.message
+        assert sol.maxcv < 1e-8, sol
+        assert sol.nfev <= 100, sol
+        assert sol.fun < self.fun(solution, 2.0) + 1e-3, sol
+
+    def test_minimize_array(self):
+        def fun_array(x, dim):
+            f = np.array(self.fun(x))
+            return np.reshape(f, (1,) * dim)
+
+        # The argument fun can return an array with a single element.
+        bounds = Bounds([4.5, 0.6], [5.0, 0.7])
+        constraints = NonlinearConstraint(self.con, 0.0, 0.0)
+        sol = minimize(
+            self.fun,
+            self.x0,
+            method='cobyqa',
+            bounds=bounds,
+            constraints=constraints,
+            options=self.options,
+        )
+        for dim in [0, 1, 2]:
+            sol_array = minimize(
+                fun_array,
+                self.x0,
+                args=(dim,),
+                method='cobyqa',
+                bounds=bounds,
+                constraints=constraints,
+                options=self.options,
+            )
+            assert_equal(sol.x, sol_array.x)
+            assert sol_array.success, sol_array.message
+            assert sol.fun == sol_array.fun
+            assert sol.maxcv == sol_array.maxcv
+            assert sol.nfev == sol_array.nfev
+            assert sol.nit == sol_array.nit
+
+        # The argument fun cannot return an array with more than one element.
+        with pytest.raises(TypeError):
+            minimize(
+                lambda x: np.array([self.fun(x), self.fun(x)]),
+                self.x0,
+                method='cobyqa',
+                bounds=bounds,
+                constraints=constraints,
+                options=self.options,
+            )
+
+    def test_minimize_maxfev(self):
+        constraints = NonlinearConstraint(self.con, 0.0, 0.0)
+        options = {'maxfev': 2}
+        sol = minimize(
+            self.fun,
+            self.x0,
+            method='cobyqa',
+            constraints=constraints,
+            options=options,
+        )
+        assert not sol.success, sol.message
+        assert sol.nfev <= 2, sol
+
+    def test_minimize_maxiter(self):
+        constraints = NonlinearConstraint(self.con, 0.0, 0.0)
+        options = {'maxiter': 2}
+        sol = minimize(
+            self.fun,
+            self.x0,
+            method='cobyqa',
+            constraints=constraints,
+            options=options,
+        )
+        assert not sol.success, sol.message
+        assert sol.nit <= 2, sol
+
+    def test_minimize_f_target(self):
+        constraints = NonlinearConstraint(self.con, 0.0, 0.0)
+        sol_ref = minimize(
+            self.fun,
+            self.x0,
+            method='cobyqa',
+            constraints=constraints,
+            options=self.options,
+        )
+        options = dict(self.options)
+        options['f_target'] = sol_ref.fun
+        sol = minimize(
+            self.fun,
+            self.x0,
+            method='cobyqa',
+            constraints=constraints,
+            options=options,
+        )
+        assert sol.success, sol.message
+        assert sol.maxcv < 1e-8, sol
+        assert sol.nfev <= sol_ref.nfev, sol
+        assert sol.fun <= sol_ref.fun, sol

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_constraint_conversion.py

@@ -0,0 +1,286 @@
+"""
+Unit test for constraint conversion
+"""
+
+import numpy as np
+from numpy.testing import (assert_array_almost_equal,
+                           assert_allclose, assert_warns, suppress_warnings)
+import pytest
+from scipy.optimize import (NonlinearConstraint, LinearConstraint,
+                            OptimizeWarning, minimize, BFGS)
+from .test_minimize_constrained import (Maratos, HyperbolicIneq, Rosenbrock,
+                                        IneqRosenbrock, EqIneqRosenbrock,
+                                        BoundedRosenbrock, Elec)
+
+
+class TestOldToNew:
+    x0 = (2, 0)
+    bnds = ((0, None), (0, None))
+    method = "trust-constr"
+
+    def test_constraint_dictionary_1(self):
+        def fun(x):
+            return (x[0] - 1) ** 2 + (x[1] - 2.5) ** 2
+        cons = ({'type': 'ineq', 'fun': lambda x: x[0] - 2 * x[1] + 2},
+                {'type': 'ineq', 'fun': lambda x: -x[0] - 2 * x[1] + 6},
+                {'type': 'ineq', 'fun': lambda x: -x[0] + 2 * x[1] + 2})
+
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "delta_grad == 0.0")
+            res = minimize(fun, self.x0, method=self.method,
+                           bounds=self.bnds, constraints=cons)
+        assert_allclose(res.x, [1.4, 1.7], rtol=1e-4)
+        assert_allclose(res.fun, 0.8, rtol=1e-4)
+
+    def test_constraint_dictionary_2(self):
+        def fun(x):
+            return (x[0] - 1) ** 2 + (x[1] - 2.5) ** 2
+        cons = {'type': 'eq',
+                'fun': lambda x, p1, p2: p1*x[0] - p2*x[1],
+                'args': (1, 1.1),
+                'jac': lambda x, p1, p2: np.array([[p1, -p2]])}
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "delta_grad == 0.0")
+            res = minimize(fun, self.x0, method=self.method,
+                           bounds=self.bnds, constraints=cons)
+        assert_allclose(res.x, [1.7918552, 1.62895927])
+        assert_allclose(res.fun, 1.3857466063348418)
+
+    def test_constraint_dictionary_3(self):
+        def fun(x):
+            return (x[0] - 1) ** 2 + (x[1] - 2.5) ** 2
+        cons = [{'type': 'ineq', 'fun': lambda x: x[0] - 2 * x[1] + 2},
+                NonlinearConstraint(lambda x: x[0] - x[1], 0, 0)]
+
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "delta_grad == 0.0")
+            res = minimize(fun, self.x0, method=self.method,
+                           bounds=self.bnds, constraints=cons)
+        assert_allclose(res.x, [1.75, 1.75], rtol=1e-4)
+        assert_allclose(res.fun, 1.125, rtol=1e-4)
+
+
+class TestNewToOld:
+    @pytest.mark.fail_slow(2)
+    def test_multiple_constraint_objects(self, num_parallel_threads):
+        def fun(x):
+            return (x[0] - 1) ** 2 + (x[1] - 2.5) ** 2 + (x[2] - 0.75) ** 2
+        x0 = [2, 0, 1]
+        coni = []  # only inequality constraints (can use cobyla)
+        methods = ["slsqp", "cobyla", "cobyqa", "trust-constr"]
+
+        # mixed old and new
+        coni.append([{'type': 'ineq', 'fun': lambda x: x[0] - 2 * x[1] + 2},
+                     NonlinearConstraint(lambda x: x[0] - x[1], -1, 1)])
+
+        coni.append([LinearConstraint([1, -2, 0], -2, np.inf),
+                     NonlinearConstraint(lambda x: x[0] - x[1], -1, 1)])
+
+        coni.append([NonlinearConstraint(lambda x: x[0] - 2 * x[1] + 2, 0, np.inf),
+                     NonlinearConstraint(lambda x: x[0] - x[1], -1, 1)])
+
+        for con in coni:
+            funs = {}
+            for method in methods:
+                with suppress_warnings() as sup:
+                    sup.filter(UserWarning)
+                    result = minimize(fun, x0, method=method, constraints=con)
+                    funs[method] = result.fun
+            assert_allclose(funs['slsqp'], funs['trust-constr'], rtol=1e-4)
+            assert_allclose(funs['cobyla'], funs['trust-constr'], rtol=1e-4)
+            if num_parallel_threads == 1:
+                assert_allclose(funs['cobyqa'], funs['trust-constr'],
+                                rtol=1e-4)
+
+    @pytest.mark.fail_slow(20)
+    def test_individual_constraint_objects(self, num_parallel_threads):
+        def fun(x):
+            return (x[0] - 1) ** 2 + (x[1] - 2.5) ** 2 + (x[2] - 0.75) ** 2
+        x0 = [2, 0, 1]
+
+        cone = []  # with equality constraints (can't use cobyla)
+        coni = []  # only inequality constraints (can use cobyla)
+        methods = ["slsqp", "cobyla", "cobyqa", "trust-constr"]
+
+        # nonstandard data types for constraint equality bounds
+        cone.append(NonlinearConstraint(lambda x: x[0] - x[1], 1, 1))
+        cone.append(NonlinearConstraint(lambda x: x[0] - x[1], [1.21], [1.21]))
+        cone.append(NonlinearConstraint(lambda x: x[0] - x[1],
+                                        1.21, np.array([1.21])))
+
+        # multiple equalities
+        cone.append(NonlinearConstraint(
+                    lambda x: [x[0] - x[1], x[1] - x[2]],
+                    1.21, 1.21))  # two same equalities
+        cone.append(NonlinearConstraint(
+                    lambda x: [x[0] - x[1], x[1] - x[2]],
+                    [1.21, 1.4], [1.21, 1.4]))  # two different equalities
+        cone.append(NonlinearConstraint(
+                    lambda x: [x[0] - x[1], x[1] - x[2]],
+                    [1.21, 1.21], 1.21))  # equality specified two ways
+        cone.append(NonlinearConstraint(
+                    lambda x: [x[0] - x[1], x[1] - x[2]],
+                    [1.21, -np.inf], [1.21, np.inf]))  # equality + unbounded
+
+        # nonstandard data types for constraint inequality bounds
+        coni.append(NonlinearConstraint(lambda x: x[0] - x[1], 1.21, np.inf))
+        coni.append(NonlinearConstraint(lambda x: x[0] - x[1], [1.21], np.inf))
+        coni.append(NonlinearConstraint(lambda x: x[0] - x[1],
+                                        1.21, np.array([np.inf])))
+        coni.append(NonlinearConstraint(lambda x: x[0] - x[1], -np.inf, -3))
+        coni.append(NonlinearConstraint(lambda x: x[0] - x[1],
+                                        np.array(-np.inf), -3))
+
+        # multiple inequalities/equalities
+        coni.append(NonlinearConstraint(
+                    lambda x: [x[0] - x[1], x[1] - x[2]],
+                    1.21, np.inf))  # two same inequalities
+        cone.append(NonlinearConstraint(
+                    lambda x: [x[0] - x[1], x[1] - x[2]],
+                    [1.21, -np.inf], [1.21, 1.4]))  # mixed equality/inequality
+        coni.append(NonlinearConstraint(
+                    lambda x: [x[0] - x[1], x[1] - x[2]],
+                    [1.1, .8], [1.2, 1.4]))  # bounded above and below
+        coni.append(NonlinearConstraint(
+                    lambda x: [x[0] - x[1], x[1] - x[2]],
+                    [-1.2, -1.4], [-1.1, -.8]))  # - bounded above and below
+
+        # quick check of LinearConstraint class (very little new code to test)
+        cone.append(LinearConstraint([1, -1, 0], 1.21, 1.21))
+        cone.append(LinearConstraint([[1, -1, 0], [0, 1, -1]], 1.21, 1.21))
+        cone.append(LinearConstraint([[1, -1, 0], [0, 1, -1]],
+                                     [1.21, -np.inf], [1.21, 1.4]))
+
+        for con in coni:
+            funs = {}
+            for method in methods:
+                with suppress_warnings() as sup:
+                    sup.filter(UserWarning)
+                    result = minimize(fun, x0, method=method, constraints=con)
+                    funs[method] = result.fun
+            assert_allclose(funs['slsqp'], funs['trust-constr'], rtol=1e-3)
+            assert_allclose(funs['cobyla'], funs['trust-constr'], rtol=1e-3)
+            if num_parallel_threads == 1:
+                assert_allclose(funs['cobyqa'], funs['trust-constr'],
+                                rtol=1e-3)
+
+        for con in cone:
+            funs = {}
+            for method in [method for method in methods if method != 'cobyla']:
+                with suppress_warnings() as sup:
+                    sup.filter(UserWarning)
+                    result = minimize(fun, x0, method=method, constraints=con)
+                    funs[method] = result.fun
+            assert_allclose(funs['slsqp'], funs['trust-constr'], rtol=1e-3)
+            if num_parallel_threads == 1:
+                assert_allclose(funs['cobyqa'], funs['trust-constr'],
+                                rtol=1e-3)
+
+
+class TestNewToOldSLSQP:
+    method = 'slsqp'
+    elec = Elec(n_electrons=2)
+    elec.x_opt = np.array([-0.58438468, 0.58438466, 0.73597047,
+                           -0.73597044, 0.34180668, -0.34180667])
+    brock = BoundedRosenbrock()
+    brock.x_opt = [0, 0]
+    list_of_problems = [Maratos(),
+                        HyperbolicIneq(),
+                        Rosenbrock(),
+                        IneqRosenbrock(),
+                        EqIneqRosenbrock(),
+                        elec,
+                        brock
+                        ]
+
+    def test_list_of_problems(self):
+
+        for prob in self.list_of_problems:
+
+            with suppress_warnings() as sup:
+                sup.filter(UserWarning)
+                result = minimize(prob.fun, prob.x0,
+                                  method=self.method,
+                                  bounds=prob.bounds,
+                                  constraints=prob.constr)
+
+            assert_array_almost_equal(result.x, prob.x_opt, decimal=3)
+
+    @pytest.mark.thread_unsafe
+    def test_warn_mixed_constraints(self):
+        # warns about inefficiency of mixed equality/inequality constraints
+        def fun(x):
+            return (x[0] - 1) ** 2 + (x[1] - 2.5) ** 2 + (x[2] - 0.75) ** 2
+        cons = NonlinearConstraint(lambda x: [x[0]**2 - x[1], x[1] - x[2]],
+                                   [1.1, .8], [1.1, 1.4])
+        bnds = ((0, None), (0, None), (0, None))
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "delta_grad == 0.0")
+            assert_warns(OptimizeWarning, minimize, fun, (2, 0, 1),
+                         method=self.method, bounds=bnds, constraints=cons)
+
+    @pytest.mark.thread_unsafe
+    def test_warn_ignored_options(self):
+        # warns about constraint options being ignored
+        def fun(x):
+            return (x[0] - 1) ** 2 + (x[1] - 2.5) ** 2 + (x[2] - 0.75) ** 2
+        x0 = (2, 0, 1)
+
+        if self.method == "slsqp":
+            bnds = ((0, None), (0, None), (0, None))
+        else:
+            bnds = None
+
+        cons = NonlinearConstraint(lambda x: x[0], 2, np.inf)
+        res = minimize(fun, x0, method=self.method,
+                       bounds=bnds, constraints=cons)
+        # no warnings without constraint options
+        assert_allclose(res.fun, 1)
+
+        cons = LinearConstraint([1, 0, 0], 2, np.inf)
+        res = minimize(fun, x0, method=self.method,
+                       bounds=bnds, constraints=cons)
+        # no warnings without constraint options
+        assert_allclose(res.fun, 1)
+
+        cons = []
+        cons.append(NonlinearConstraint(lambda x: x[0]**2, 2, np.inf,
+                                        keep_feasible=True))
+        cons.append(NonlinearConstraint(lambda x: x[0]**2, 2, np.inf,
+                                        hess=BFGS()))
+        cons.append(NonlinearConstraint(lambda x: x[0]**2, 2, np.inf,
+                                        finite_diff_jac_sparsity=42))
+        cons.append(NonlinearConstraint(lambda x: x[0]**2, 2, np.inf,
+                                        finite_diff_rel_step=42))
+        cons.append(LinearConstraint([1, 0, 0], 2, np.inf,
+                                     keep_feasible=True))
+        for con in cons:
+            assert_warns(OptimizeWarning, minimize, fun, x0,
+                         method=self.method, bounds=bnds, constraints=cons)
+
+
+class TestNewToOldCobyla:
+    method = 'cobyla'
+
+    list_of_problems = [
+                        Elec(n_electrons=2),
+                        Elec(n_electrons=4),
+                        ]
+
+    @pytest.mark.slow
+    def test_list_of_problems(self):
+
+        for prob in self.list_of_problems:
+
+            with suppress_warnings() as sup:
+                sup.filter(UserWarning)
+                truth = minimize(prob.fun, prob.x0,
+                                 method='trust-constr',
+                                 bounds=prob.bounds,
+                                 constraints=prob.constr)
+                result = minimize(prob.fun, prob.x0,
+                                  method=self.method,
+                                  bounds=prob.bounds,
+                                  constraints=prob.constr)
+
+            assert_allclose(result.fun, truth.fun, rtol=1e-3)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_constraints.py

@@ -0,0 +1,255 @@
+import pytest
+import numpy as np
+from numpy.testing import TestCase, assert_array_equal
+import scipy.sparse as sps
+from scipy.optimize._constraints import (
+    Bounds, LinearConstraint, NonlinearConstraint, PreparedConstraint,
+    new_bounds_to_old, old_bound_to_new, strict_bounds)
+
+
+class TestStrictBounds(TestCase):
+    def test_scalarvalue_unique_enforce_feasibility(self):
+        m = 3
+        lb = 2
+        ub = 4
+        enforce_feasibility = False
+        strict_lb, strict_ub = strict_bounds(lb, ub,
+                                             enforce_feasibility,
+                                             m)
+        assert_array_equal(strict_lb, [-np.inf, -np.inf, -np.inf])
+        assert_array_equal(strict_ub, [np.inf, np.inf, np.inf])
+
+        enforce_feasibility = True
+        strict_lb, strict_ub = strict_bounds(lb, ub,
+                                             enforce_feasibility,
+                                             m)
+        assert_array_equal(strict_lb, [2, 2, 2])
+        assert_array_equal(strict_ub, [4, 4, 4])
+
+    def test_vectorvalue_unique_enforce_feasibility(self):
+        m = 3
+        lb = [1, 2, 3]
+        ub = [4, 5, 6]
+        enforce_feasibility = False
+        strict_lb, strict_ub = strict_bounds(lb, ub,
+                                              enforce_feasibility,
+                                              m)
+        assert_array_equal(strict_lb, [-np.inf, -np.inf, -np.inf])
+        assert_array_equal(strict_ub, [np.inf, np.inf, np.inf])
+
+        enforce_feasibility = True
+        strict_lb, strict_ub = strict_bounds(lb, ub,
+                                              enforce_feasibility,
+                                              m)
+        assert_array_equal(strict_lb, [1, 2, 3])
+        assert_array_equal(strict_ub, [4, 5, 6])
+
+    def test_scalarvalue_vector_enforce_feasibility(self):
+        m = 3
+        lb = 2
+        ub = 4
+        enforce_feasibility = [False, True, False]
+        strict_lb, strict_ub = strict_bounds(lb, ub,
+                                             enforce_feasibility,
+                                             m)
+        assert_array_equal(strict_lb, [-np.inf, 2, -np.inf])
+        assert_array_equal(strict_ub, [np.inf, 4, np.inf])
+
+    def test_vectorvalue_vector_enforce_feasibility(self):
+        m = 3
+        lb = [1, 2, 3]
+        ub = [4, 6, np.inf]
+        enforce_feasibility = [True, False, True]
+        strict_lb, strict_ub = strict_bounds(lb, ub,
+                                             enforce_feasibility,
+                                             m)
+        assert_array_equal(strict_lb, [1, -np.inf, 3])
+        assert_array_equal(strict_ub, [4, np.inf, np.inf])
+
+
+def test_prepare_constraint_infeasible_x0():
+    lb = np.array([0, 20, 30])
+    ub = np.array([0.5, np.inf, 70])
+    x0 = np.array([1, 2, 3])
+    enforce_feasibility = np.array([False, True, True], dtype=bool)
+    bounds = Bounds(lb, ub, enforce_feasibility)
+    pytest.raises(ValueError, PreparedConstraint, bounds, x0)
+
+    pc = PreparedConstraint(Bounds(lb, ub), [1, 2, 3])
+    assert (pc.violation([1, 2, 3]) > 0).any()
+    assert (pc.violation([0.25, 21, 31]) == 0).all()
+
+    x0 = np.array([1, 2, 3, 4])
+    A = np.array([[1, 2, 3, 4], [5, 0, 0, 6], [7, 0, 8, 0]])
+    enforce_feasibility = np.array([True, True, True], dtype=bool)
+    linear = LinearConstraint(A, -np.inf, 0, enforce_feasibility)
+    pytest.raises(ValueError, PreparedConstraint, linear, x0)
+
+    pc = PreparedConstraint(LinearConstraint(A, -np.inf, 0),
+                            [1, 2, 3, 4])
+    assert (pc.violation([1, 2, 3, 4]) > 0).any()
+    assert (pc.violation([-10, 2, -10, 4]) == 0).all()
+
+    def fun(x):
+        return A.dot(x)
+
+    def jac(x):
+        return A
+
+    def hess(x, v):
+        return sps.csr_array((4, 4))
+
+    nonlinear = NonlinearConstraint(fun, -np.inf, 0, jac, hess,
+                                    enforce_feasibility)
+    pytest.raises(ValueError, PreparedConstraint, nonlinear, x0)
+
+    pc = PreparedConstraint(nonlinear, [-10, 2, -10, 4])
+    assert (pc.violation([1, 2, 3, 4]) > 0).any()
+    assert (pc.violation([-10, 2, -10, 4]) == 0).all()
+
+
+def test_violation():
+    def cons_f(x):
+        return np.array([x[0] ** 2 + x[1], x[0] ** 2 - x[1]])
+
+    nlc = NonlinearConstraint(cons_f, [-1, -0.8500], [2, 2])
+    pc = PreparedConstraint(nlc, [0.5, 1])
+
+    assert_array_equal(pc.violation([0.5, 1]), [0., 0.])
+
+    np.testing.assert_almost_equal(pc.violation([0.5, 1.2]), [0., 0.1])
+
+    np.testing.assert_almost_equal(pc.violation([1.2, 1.2]), [0.64, 0])
+
+    np.testing.assert_almost_equal(pc.violation([0.1, -1.2]), [0.19, 0])
+
+    np.testing.assert_almost_equal(pc.violation([0.1, 2]), [0.01, 1.14])
+
+
+def test_new_bounds_to_old():
+    lb = np.array([-np.inf, 2, 3])
+    ub = np.array([3, np.inf, 10])
+
+    bounds = [(None, 3), (2, None), (3, 10)]
+    assert_array_equal(new_bounds_to_old(lb, ub, 3), bounds)
+
+    bounds_single_lb = [(-1, 3), (-1, None), (-1, 10)]
+    assert_array_equal(new_bounds_to_old(-1, ub, 3), bounds_single_lb)
+
+    bounds_no_lb = [(None, 3), (None, None), (None, 10)]
+    assert_array_equal(new_bounds_to_old(-np.inf, ub, 3), bounds_no_lb)
+
+    bounds_single_ub = [(None, 20), (2, 20), (3, 20)]
+    assert_array_equal(new_bounds_to_old(lb, 20, 3), bounds_single_ub)
+
+    bounds_no_ub = [(None, None), (2, None), (3, None)]
+    assert_array_equal(new_bounds_to_old(lb, np.inf, 3), bounds_no_ub)
+
+    bounds_single_both = [(1, 2), (1, 2), (1, 2)]
+    assert_array_equal(new_bounds_to_old(1, 2, 3), bounds_single_both)
+
+    bounds_no_both = [(None, None), (None, None), (None, None)]
+    assert_array_equal(new_bounds_to_old(-np.inf, np.inf, 3), bounds_no_both)
+
+
+def test_old_bounds_to_new():
+    bounds = ([1, 2], (None, 3), (-1, None))
+    lb_true = np.array([1, -np.inf, -1])
+    ub_true = np.array([2, 3, np.inf])
+
+    lb, ub = old_bound_to_new(bounds)
+    assert_array_equal(lb, lb_true)
+    assert_array_equal(ub, ub_true)
+
+    bounds = [(-np.inf, np.inf), (np.array([1]), np.array([1]))]
+    lb, ub = old_bound_to_new(bounds)
+
+    assert_array_equal(lb, [-np.inf, 1])
+    assert_array_equal(ub, [np.inf, 1])
+
+
+class TestBounds:
+    def test_repr(self):
+        # so that eval works
+        from numpy import array, inf  # noqa: F401
+        for args in (
+            (-1.0, 5.0),
+            (-1.0, np.inf, True),
+            (np.array([1.0, -np.inf]), np.array([2.0, np.inf])),
+            (np.array([1.0, -np.inf]), np.array([2.0, np.inf]),
+             np.array([True, False])),
+        ):
+            bounds = Bounds(*args)
+            bounds2 = eval(repr(Bounds(*args)))
+            assert_array_equal(bounds.lb, bounds2.lb)
+            assert_array_equal(bounds.ub, bounds2.ub)
+            assert_array_equal(bounds.keep_feasible, bounds2.keep_feasible)
+
+    def test_array(self):
+        # gh13501
+        b = Bounds(lb=[0.0, 0.0], ub=[1.0, 1.0])
+        assert isinstance(b.lb, np.ndarray)
+        assert isinstance(b.ub, np.ndarray)
+
+    def test_defaults(self):
+        b1 = Bounds()
+        b2 = Bounds(np.asarray(-np.inf), np.asarray(np.inf))
+        assert b1.lb == b2.lb
+        assert b1.ub == b2.ub
+
+    def test_input_validation(self):
+        message = "Lower and upper bounds must be dense arrays."
+        with pytest.raises(ValueError, match=message):
+            Bounds(sps.coo_array([1, 2]), [1, 2])
+        with pytest.raises(ValueError, match=message):
+            Bounds([1, 2], sps.coo_array([1, 2]))
+
+        message = "`keep_feasible` must be a dense array."
+        with pytest.raises(ValueError, match=message):
+            Bounds([1, 2], [1, 2], keep_feasible=sps.coo_array([True, True]))
+
+        message = "`lb`, `ub`, and `keep_feasible` must be broadcastable."
+        with pytest.raises(ValueError, match=message):
+            Bounds([1, 2], [1, 2, 3])
+
+    def test_residual(self):
+        bounds = Bounds(-2, 4)
+        x0 = [-1, 2]
+        np.testing.assert_allclose(bounds.residual(x0), ([1, 4], [5, 2]))
+
+
+class TestLinearConstraint:
+    def test_defaults(self):
+        A = np.eye(4)
+        lc = LinearConstraint(A)
+        lc2 = LinearConstraint(A, -np.inf, np.inf)
+        assert_array_equal(lc.lb, lc2.lb)
+        assert_array_equal(lc.ub, lc2.ub)
+
+    def test_input_validation(self):
+        A = np.eye(4)
+        message = "`lb`, `ub`, and `keep_feasible` must be broadcastable"
+        with pytest.raises(ValueError, match=message):
+            LinearConstraint(A, [1, 2], [1, 2, 3])
+
+        message = "Constraint limits must be dense arrays"
+        with pytest.raises(ValueError, match=message):
+            LinearConstraint(A, sps.coo_array([1, 2]), [2, 3])
+        with pytest.raises(ValueError, match=message):
+            LinearConstraint(A, [1, 2], sps.coo_array([2, 3]))
+
+        message = "`keep_feasible` must be a dense array"
+        with pytest.raises(ValueError, match=message):
+            keep_feasible = sps.coo_array([True, True])
+            LinearConstraint(A, [1, 2], [2, 3], keep_feasible=keep_feasible)
+
+        A = np.empty((4, 3, 5))
+        message = "`A` must have exactly two dimensions."
+        with pytest.raises(ValueError, match=message):
+            LinearConstraint(A)
+
+    def test_residual(self):
+        A = np.eye(2)
+        lc = LinearConstraint(A, -2, 4)
+        x0 = [-1, 2]
+        np.testing.assert_allclose(lc.residual(x0), ([1, 4], [5, 2]))

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_cython_optimize.py

@@ -0,0 +1,92 @@
+"""
+Test Cython optimize zeros API functions: ``bisect``, ``ridder``, ``brenth``,
+and ``brentq`` in `scipy.optimize.cython_optimize`, by finding the roots of a
+3rd order polynomial given a sequence of constant terms, ``a0``, and fixed 1st,
+2nd, and 3rd order terms in ``args``.
+
+.. math::
+
+    f(x, a0, args) =  ((args[2]*x + args[1])*x + args[0])*x + a0
+
+The 3rd order polynomial function is written in Cython and called in a Python
+wrapper named after the zero function. See the private ``_zeros`` Cython module
+in `scipy.optimize.cython_optimze` for more information.
+"""
+
+import numpy.testing as npt
+from scipy.optimize.cython_optimize import _zeros
+
+# CONSTANTS
+# Solve x**3 - A0 = 0  for A0 = [2.0, 2.1, ..., 2.9].
+# The ARGS have 3 elements just to show how this could be done for any cubic
+# polynomial.
+A0 = tuple(-2.0 - x/10.0 for x in range(10))  # constant term
+ARGS = (0.0, 0.0, 1.0)  # 1st, 2nd, and 3rd order terms
+XLO, XHI = 0.0, 2.0  # first and second bounds of zeros functions
+# absolute and relative tolerances and max iterations for zeros functions
+XTOL, RTOL, MITR = 0.001, 0.001, 10
+EXPECTED = [(-a0) ** (1.0/3.0) for a0 in A0]
+# = [1.2599210498948732,
+#    1.2805791649874942,
+#    1.300591446851387,
+#    1.3200061217959123,
+#    1.338865900164339,
+#    1.3572088082974532,
+#    1.375068867074141,
+#    1.3924766500838337,
+#    1.4094597464129783,
+#    1.4260431471424087]
+
+
+# test bisect
+def test_bisect():
+    npt.assert_allclose(
+        EXPECTED,
+        list(
+            _zeros.loop_example('bisect', A0, ARGS, XLO, XHI, XTOL, RTOL, MITR)
+        ),
+        rtol=RTOL, atol=XTOL
+    )
+
+
+# test ridder
+def test_ridder():
+    npt.assert_allclose(
+        EXPECTED,
+        list(
+            _zeros.loop_example('ridder', A0, ARGS, XLO, XHI, XTOL, RTOL, MITR)
+        ),
+        rtol=RTOL, atol=XTOL
+    )
+
+
+# test brenth
+def test_brenth():
+    npt.assert_allclose(
+        EXPECTED,
+        list(
+            _zeros.loop_example('brenth', A0, ARGS, XLO, XHI, XTOL, RTOL, MITR)
+        ),
+        rtol=RTOL, atol=XTOL
+    )
+
+
+# test brentq
+def test_brentq():
+    npt.assert_allclose(
+        EXPECTED,
+        list(
+            _zeros.loop_example('brentq', A0, ARGS, XLO, XHI, XTOL, RTOL, MITR)
+        ),
+        rtol=RTOL, atol=XTOL
+    )
+
+
+# test brentq with full output
+def test_brentq_full_output():
+    output = _zeros.full_output_example(
+        (A0[0],) + ARGS, XLO, XHI, XTOL, RTOL, MITR)
+    npt.assert_allclose(EXPECTED[0], output['root'], rtol=RTOL, atol=XTOL)
+    npt.assert_equal(6, output['iterations'])
+    npt.assert_equal(7, output['funcalls'])
+    npt.assert_equal(0, output['error_num'])

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_direct.py

@@ -0,0 +1,321 @@
+"""
+Unit test for DIRECT optimization algorithm.
+"""
+from numpy.testing import (assert_allclose,
+                           assert_array_less)
+import pytest
+import numpy as np
+from scipy.optimize import direct, Bounds
+import threading
+
+
+class TestDIRECT:
+
+    def setup_method(self):
+        self.fun_calls = threading.local()
+        self.bounds_sphere = 4*[(-2, 3)]
+        self.optimum_sphere_pos = np.zeros((4, ))
+        self.optimum_sphere = 0.0
+        self.bounds_stylinski_tang = Bounds([-4., -4.], [4., 4.])
+        self.maxiter = 1000
+
+    # test functions
+    def sphere(self, x):
+        if not hasattr(self.fun_calls, 'c'):
+            self.fun_calls.c = 0
+        self.fun_calls.c += 1
+        return np.square(x).sum()
+
+    def inv(self, x):
+        if np.sum(x) == 0:
+            raise ZeroDivisionError()
+        return 1/np.sum(x)
+
+    def nan_fun(self, x):
+        return np.nan
+
+    def inf_fun(self, x):
+        return np.inf
+
+    def styblinski_tang(self, pos):
+        x, y = pos
+        return 0.5 * (x**4 - 16 * x**2 + 5 * x + y**4 - 16 * y**2 + 5 * y)
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_direct(self, locally_biased):
+        res = direct(self.sphere, self.bounds_sphere,
+                     locally_biased=locally_biased)
+
+        # test accuracy
+        assert_allclose(res.x, self.optimum_sphere_pos,
+                        rtol=1e-3, atol=1e-3)
+        assert_allclose(res.fun, self.optimum_sphere, atol=1e-5, rtol=1e-5)
+
+        # test that result lies within bounds
+        _bounds = np.asarray(self.bounds_sphere)
+        assert_array_less(_bounds[:, 0], res.x)
+        assert_array_less(res.x, _bounds[:, 1])
+
+        # test number of function evaluations. Original DIRECT overshoots by
+        # up to 500 evaluations in last iteration
+        assert res.nfev <= 1000 * (len(self.bounds_sphere) + 1)
+        # test that number of function evaluations is correct
+        assert res.nfev == self.fun_calls.c
+
+        # test that number of iterations is below supplied maximum
+        assert res.nit <= self.maxiter
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_direct_callback(self, locally_biased):
+        # test that callback does not change the result
+        res = direct(self.sphere, self.bounds_sphere,
+                     locally_biased=locally_biased)
+
+        def callback(x):
+            x = 2*x
+            dummy = np.square(x)
+            print("DIRECT minimization algorithm callback test")
+            return dummy
+
+        res_callback = direct(self.sphere, self.bounds_sphere,
+                              locally_biased=locally_biased,
+                              callback=callback)
+
+        assert_allclose(res.x, res_callback.x)
+
+        assert res.nit == res_callback.nit
+        assert res.nfev == res_callback.nfev
+        assert res.status == res_callback.status
+        assert res.success == res_callback.success
+        assert res.fun == res_callback.fun
+        assert_allclose(res.x, res_callback.x)
+        assert res.message == res_callback.message
+
+        # test accuracy
+        assert_allclose(res_callback.x, self.optimum_sphere_pos,
+                        rtol=1e-3, atol=1e-3)
+        assert_allclose(res_callback.fun, self.optimum_sphere,
+                        atol=1e-5, rtol=1e-5)
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_exception(self, locally_biased):
+        bounds = 4*[(-10, 10)]
+        with pytest.raises(ZeroDivisionError):
+            direct(self.inv, bounds=bounds,
+                   locally_biased=locally_biased)
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_nan(self, locally_biased):
+        bounds = 4*[(-10, 10)]
+        direct(self.nan_fun, bounds=bounds,
+               locally_biased=locally_biased)
+
+    @pytest.mark.parametrize("len_tol", [1e-3, 1e-4])
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_len_tol(self, len_tol, locally_biased):
+        bounds = 4*[(-10., 10.)]
+        res = direct(self.sphere, bounds=bounds, len_tol=len_tol,
+                     vol_tol=1e-30, locally_biased=locally_biased)
+        assert res.status == 5
+        assert res.success
+        assert_allclose(res.x, np.zeros((4, )))
+        message = ("The side length measure of the hyperrectangle containing "
+                   "the lowest function value found is below "
+                   f"len_tol={len_tol}")
+        assert res.message == message
+
+    @pytest.mark.parametrize("vol_tol", [1e-6, 1e-8])
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_vol_tol(self, vol_tol, locally_biased):
+        bounds = 4*[(-10., 10.)]
+        res = direct(self.sphere, bounds=bounds, vol_tol=vol_tol,
+                     len_tol=0., locally_biased=locally_biased)
+        assert res.status == 4
+        assert res.success
+        assert_allclose(res.x, np.zeros((4, )))
+        message = ("The volume of the hyperrectangle containing the lowest "
+                   f"function value found is below vol_tol={vol_tol}")
+        assert res.message == message
+
+    @pytest.mark.parametrize("f_min_rtol", [1e-3, 1e-5, 1e-7])
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_f_min(self, f_min_rtol, locally_biased):
+        # test that desired function value is reached within
+        # relative tolerance of f_min_rtol
+        f_min = 1.
+        bounds = 4*[(-2., 10.)]
+        res = direct(self.sphere, bounds=bounds, f_min=f_min,
+                     f_min_rtol=f_min_rtol,
+                     locally_biased=locally_biased)
+        assert res.status == 3
+        assert res.success
+        assert res.fun < f_min * (1. + f_min_rtol)
+        message = ("The best function value found is within a relative "
+                   f"error={f_min_rtol} of the (known) global optimum f_min")
+        assert res.message == message
+
+    def circle_with_args(self, x, a, b):
+        return np.square(x[0] - a) + np.square(x[1] - b).sum()
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_f_circle_with_args(self, locally_biased):
+        bounds = 2*[(-2.0, 2.0)]
+
+        res = direct(self.circle_with_args, bounds, args=(1, 1), maxfun=1250,
+                     locally_biased=locally_biased)
+        assert_allclose(res.x, np.array([1., 1.]), rtol=1e-5)
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_failure_maxfun(self, locally_biased):
+        # test that if optimization runs for the maximal number of
+        # evaluations, success = False is returned
+
+        maxfun = 100
+        result = direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                        maxfun=maxfun, locally_biased=locally_biased)
+        assert result.success is False
+        assert result.status == 1
+        assert result.nfev >= maxfun
+        message = ("Number of function evaluations done is "
+                   f"larger than maxfun={maxfun}")
+        assert result.message == message
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_failure_maxiter(self, locally_biased):
+        # test that if optimization runs for the maximal number of
+        # iterations, success = False is returned
+
+        maxiter = 10
+        result = direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                        maxiter=maxiter, locally_biased=locally_biased)
+        assert result.success is False
+        assert result.status == 2
+        assert result.nit >= maxiter
+        message = f"Number of iterations is larger than maxiter={maxiter}"
+        assert result.message == message
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_bounds_variants(self, locally_biased):
+        # test that new and old bounds yield same result
+
+        lb = [-6., 1., -5.]
+        ub = [-1., 3., 5.]
+        x_opt = np.array([-1., 1., 0.])
+        bounds_old = list(zip(lb, ub))
+        bounds_new = Bounds(lb, ub)
+
+        res_old_bounds = direct(self.sphere, bounds_old,
+                                locally_biased=locally_biased)
+        res_new_bounds = direct(self.sphere, bounds_new,
+                                locally_biased=locally_biased)
+
+        assert res_new_bounds.nfev == res_old_bounds.nfev
+        assert res_new_bounds.message == res_old_bounds.message
+        assert res_new_bounds.success == res_old_bounds.success
+        assert res_new_bounds.nit == res_old_bounds.nit
+        assert_allclose(res_new_bounds.x, res_old_bounds.x)
+        assert_allclose(res_new_bounds.x, x_opt, rtol=1e-2)
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    @pytest.mark.parametrize("eps", [1e-5, 1e-4, 1e-3])
+    def test_epsilon(self, eps, locally_biased):
+        result = direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                        eps=eps, vol_tol=1e-6,
+                        locally_biased=locally_biased)
+        assert result.status == 4
+        assert result.success
+
+    @pytest.mark.xslow
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_no_segmentation_fault(self, locally_biased):
+        # test that an excessive number of function evaluations
+        # does not result in segmentation fault
+        bounds = [(-5., 20.)] * 100
+        result = direct(self.sphere, bounds, maxfun=10000000,
+                        maxiter=1000000, locally_biased=locally_biased)
+        assert result is not None
+
+    @pytest.mark.parametrize("locally_biased", [True, False])
+    def test_inf_fun(self, locally_biased):
+        # test that an objective value of infinity does not crash DIRECT
+        bounds = [(-5., 5.)] * 2
+        result = direct(self.inf_fun, bounds,
+                        locally_biased=locally_biased)
+        assert result is not None
+
+    @pytest.mark.parametrize("len_tol", [-1, 2])
+    def test_len_tol_validation(self, len_tol):
+        error_msg = "len_tol must be between 0 and 1."
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                   len_tol=len_tol)
+
+    @pytest.mark.parametrize("vol_tol", [-1, 2])
+    def test_vol_tol_validation(self, vol_tol):
+        error_msg = "vol_tol must be between 0 and 1."
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                   vol_tol=vol_tol)
+
+    @pytest.mark.parametrize("f_min_rtol", [-1, 2])
+    def test_fmin_rtol_validation(self, f_min_rtol):
+        error_msg = "f_min_rtol must be between 0 and 1."
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                   f_min_rtol=f_min_rtol, f_min=0.)
+
+    @pytest.mark.parametrize("maxfun", [1.5, "string", (1, 2)])
+    def test_maxfun_wrong_type(self, maxfun):
+        error_msg = "maxfun must be of type int."
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                   maxfun=maxfun)
+
+    @pytest.mark.parametrize("maxiter", [1.5, "string", (1, 2)])
+    def test_maxiter_wrong_type(self, maxiter):
+        error_msg = "maxiter must be of type int."
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                   maxiter=maxiter)
+
+    def test_negative_maxiter(self):
+        error_msg = "maxiter must be > 0."
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                   maxiter=-1)
+
+    def test_negative_maxfun(self):
+        error_msg = "maxfun must be > 0."
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                   maxfun=-1)
+
+    @pytest.mark.parametrize("bounds", ["bounds", 2., 0])
+    def test_invalid_bounds_type(self, bounds):
+        error_msg = ("bounds must be a sequence or "
+                     "instance of Bounds class")
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, bounds)
+
+    @pytest.mark.parametrize("bounds",
+                             [Bounds([-1., -1], [-2, 1]),
+                              Bounds([-np.nan, -1], [-2, np.nan]),
+                              ]
+                             )
+    def test_incorrect_bounds(self, bounds):
+        error_msg = 'Bounds are not consistent min < max'
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, bounds)
+
+    def test_inf_bounds(self):
+        error_msg = 'Bounds must not be inf.'
+        bounds = Bounds([-np.inf, -1], [-2, np.inf])
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, bounds)
+
+    @pytest.mark.parametrize("locally_biased", ["bias", [0, 0], 2.])
+    def test_locally_biased_validation(self, locally_biased):
+        error_msg = 'locally_biased must be True or False.'
+        with pytest.raises(ValueError, match=error_msg):
+            direct(self.styblinski_tang, self.bounds_stylinski_tang,
+                   locally_biased=locally_biased)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_extending.py

@@ -0,0 +1,28 @@
+import os
+import platform
+import sysconfig
+
+import pytest
+
+from scipy._lib._testutils import IS_EDITABLE, _test_cython_extension, cython
+
+
+@pytest.mark.fail_slow(40)
+# essential per https://github.com/scipy/scipy/pull/20487#discussion_r1567057247
+@pytest.mark.skipif(IS_EDITABLE,
+                    reason='Editable install cannot find .pxd headers.')
+@pytest.mark.skipif((platform.system() == 'Windows' and
+                     sysconfig.get_config_var('Py_GIL_DISABLED')),
+                    reason='gh-22039')
+@pytest.mark.skipif(platform.machine() in ["wasm32", "wasm64"],
+                    reason="Can't start subprocess")
+@pytest.mark.skipif(cython is None, reason="requires cython")
+def test_cython(tmp_path):
+    srcdir = os.path.dirname(os.path.dirname(__file__))
+    extensions, extensions_cpp = _test_cython_extension(tmp_path, srcdir)
+    # actually test the cython c-extensions
+    # From docstring for scipy.optimize.cython_optimize module
+    x = extensions.brentq_example()
+    assert x == 0.6999942848231314
+    x = extensions_cpp.brentq_example()
+    assert x == 0.6999942848231314

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_hessian_update_strategy.py

@@ -0,0 +1,300 @@
+import re
+from copy import deepcopy
+
+import numpy as np
+import pytest
+from numpy.linalg import norm
+from numpy.testing import (TestCase, assert_array_almost_equal,
+                           assert_array_equal, assert_array_less)
+from scipy.optimize import (BFGS, SR1)
+
+
+class Rosenbrock:
+    """Rosenbrock function.
+
+    The following optimization problem:
+        minimize sum(100.0*(x[1:] - x[:-1]**2.0)**2.0 + (1 - x[:-1])**2.0)
+    """
+
+    def __init__(self, n=2, random_state=0):
+        rng = np.random.RandomState(random_state)
+        self.x0 = rng.uniform(-1, 1, n)
+        self.x_opt = np.ones(n)
+
+    def fun(self, x):
+        x = np.asarray(x)
+        r = np.sum(100.0 * (x[1:] - x[:-1]**2.0)**2.0 + (1 - x[:-1])**2.0,
+                   axis=0)
+        return r
+
+    def grad(self, x):
+        x = np.asarray(x)
+        xm = x[1:-1]
+        xm_m1 = x[:-2]
+        xm_p1 = x[2:]
+        der = np.zeros_like(x)
+        der[1:-1] = (200 * (xm - xm_m1**2) -
+                     400 * (xm_p1 - xm**2) * xm - 2 * (1 - xm))
+        der[0] = -400 * x[0] * (x[1] - x[0]**2) - 2 * (1 - x[0])
+        der[-1] = 200 * (x[-1] - x[-2]**2)
+        return der
+
+    def hess(self, x):
+        x = np.atleast_1d(x)
+        H = np.diag(-400 * x[:-1], 1) - np.diag(400 * x[:-1], -1)
+        diagonal = np.zeros(len(x), dtype=x.dtype)
+        diagonal[0] = 1200 * x[0]**2 - 400 * x[1] + 2
+        diagonal[-1] = 200
+        diagonal[1:-1] = 202 + 1200 * x[1:-1]**2 - 400 * x[2:]
+        H = H + np.diag(diagonal)
+        return H
+
+
+class TestHessianUpdateStrategy(TestCase):
+
+
+    def test_hessian_initialization(self):
+
+        ndims = 5
+        symmetric_matrix = np.array([[43, 24, 33, 34, 49],
+                                     [24, 36, 44, 15, 44],
+                                     [33, 44, 37, 1, 30],
+                                     [34, 15, 1, 5, 46],
+                                     [49, 44, 30, 46, 22]])
+        init_scales = (
+            ('auto', np.eye(ndims)),
+            (2, np.eye(ndims) * 2),
+            (np.arange(1, ndims + 1) * np.eye(ndims),
+             np.arange(1, ndims + 1) * np.eye(ndims)),
+            (symmetric_matrix, symmetric_matrix),)
+        for approx_type in ['hess', 'inv_hess']:
+            for init_scale, true_matrix in init_scales:
+                # large min_{denominator,curvatur} makes them skip an update,
+                # so we can have our initial matrix
+                quasi_newton = (BFGS(init_scale=init_scale,
+                                     min_curvature=1e50,
+                                     exception_strategy='skip_update'),
+                                SR1(init_scale=init_scale,
+                                    min_denominator=1e50))
+
+                for qn in quasi_newton:
+                    qn.initialize(ndims, approx_type)
+                    B = qn.get_matrix()
+
+                    assert_array_equal(B, np.eye(ndims))
+                    # don't test the auto init scale
+                    if isinstance(init_scale, str) and init_scale == 'auto':
+                        continue
+
+                    qn.update(np.ones(ndims) * 1e-5, np.arange(ndims) + 0.2)
+                    B = qn.get_matrix()
+                    assert_array_equal(B, true_matrix)
+
+    # For this list of points, it is known
+    # that no exception occur during the
+    # Hessian update. Hence no update is
+    # skiped or damped.
+
+
+    def test_initialize_catch_illegal(self):
+        ndims = 3
+        # no complex allowed
+        inits_msg_errtype = ((complex(3.14),
+                              r"float\(\) argument must be a string or a "
+                              r"(real )?number, not 'complex'",
+                              TypeError),
+
+                             (np.array([3.2, 2.3, 1.2]).astype(np.complex128),
+                              "init_scale contains complex elements, "
+                              "must be real.",
+                              TypeError),
+
+                             (np.array([[43, 24, 33],
+                                        [24, 36, 44, ],
+                                        [33, 44, 37, ]]).astype(np.complex128),
+                              "init_scale contains complex elements, "
+                              "must be real.",
+                              TypeError),
+
+                             # not square
+                             (np.array([[43, 55, 66]]),
+                              re.escape(
+                                  "If init_scale is an array, it must have the "
+                                  "dimensions of the hess/inv_hess: (3, 3)."
+                                  " Got (1, 3)."),
+                              ValueError),
+
+                             # not symmetric
+                             (np.array([[43, 24, 33],
+                                        [24.1, 36, 44, ],
+                                        [33, 44, 37, ]]),
+                              re.escape("If init_scale is an array, it must be"
+                                        " symmetric (passing scipy.linalg.issymmetric)"
+                                        " to be an approximation of a hess/inv_hess."),
+                              ValueError),
+                             )
+        for approx_type in ['hess', 'inv_hess']:
+            for init_scale, message, errortype in inits_msg_errtype:
+                # large min_{denominator,curvatur} makes it skip an update,
+                # so we can retrieve our initial matrix
+                quasi_newton = (BFGS(init_scale=init_scale),
+                                SR1(init_scale=init_scale))
+
+                for qn in quasi_newton:
+                    qn.initialize(ndims, approx_type)
+                    with pytest.raises(errortype, match=message):
+                        qn.update(np.ones(ndims), np.arange(ndims))
+
+    def test_rosenbrock_with_no_exception(self):
+        # Define auxiliary problem
+        prob = Rosenbrock(n=5)
+        # Define iteration points
+        x_list = [[0.0976270, 0.4303787, 0.2055267, 0.0897663, -0.15269040],
+                  [0.1847239, 0.0505757, 0.2123832, 0.0255081, 0.00083286],
+                  [0.2142498, -0.0188480, 0.0503822, 0.0347033, 0.03323606],
+                  [0.2071680, -0.0185071, 0.0341337, -0.0139298, 0.02881750],
+                  [0.1533055, -0.0322935, 0.0280418, -0.0083592, 0.01503699],
+                  [0.1382378, -0.0276671, 0.0266161, -0.0074060, 0.02801610],
+                  [0.1651957, -0.0049124, 0.0269665, -0.0040025, 0.02138184],
+                  [0.2354930, 0.0443711, 0.0173959, 0.0041872, 0.00794563],
+                  [0.4168118, 0.1433867, 0.0111714, 0.0126265, -0.00658537],
+                  [0.4681972, 0.2153273, 0.0225249, 0.0152704, -0.00463809],
+                  [0.6023068, 0.3346815, 0.0731108, 0.0186618, -0.00371541],
+                  [0.6415743, 0.3985468, 0.1324422, 0.0214160, -0.00062401],
+                  [0.7503690, 0.5447616, 0.2804541, 0.0539851, 0.00242230],
+                  [0.7452626, 0.5644594, 0.3324679, 0.0865153, 0.00454960],
+                  [0.8059782, 0.6586838, 0.4229577, 0.1452990, 0.00976702],
+                  [0.8549542, 0.7226562, 0.4991309, 0.2420093, 0.02772661],
+                  [0.8571332, 0.7285741, 0.5279076, 0.2824549, 0.06030276],
+                  [0.8835633, 0.7727077, 0.5957984, 0.3411303, 0.09652185],
+                  [0.9071558, 0.8299587, 0.6771400, 0.4402896, 0.17469338],
+                  [0.9190793, 0.8486480, 0.7163332, 0.5083780, 0.26107691],
+                  [0.9371223, 0.8762177, 0.7653702, 0.5773109, 0.32181041],
+                  [0.9554613, 0.9119893, 0.8282687, 0.6776178, 0.43162744],
+                  [0.9545744, 0.9099264, 0.8270244, 0.6822220, 0.45237623],
+                  [0.9688112, 0.9351710, 0.8730961, 0.7546601, 0.56622448],
+                  [0.9743227, 0.9491953, 0.9005150, 0.8086497, 0.64505437],
+                  [0.9807345, 0.9638853, 0.9283012, 0.8631675, 0.73812581],
+                  [0.9886746, 0.9777760, 0.9558950, 0.9123417, 0.82726553],
+                  [0.9899096, 0.9803828, 0.9615592, 0.9255600, 0.85822149],
+                  [0.9969510, 0.9935441, 0.9864657, 0.9726775, 0.94358663],
+                  [0.9979533, 0.9960274, 0.9921724, 0.9837415, 0.96626288],
+                  [0.9995981, 0.9989171, 0.9974178, 0.9949954, 0.99023356],
+                  [1.0002640, 1.0005088, 1.0010594, 1.0021161, 1.00386912],
+                  [0.9998903, 0.9998459, 0.9997795, 0.9995484, 0.99916305],
+                  [1.0000008, 0.9999905, 0.9999481, 0.9998903, 0.99978047],
+                  [1.0000004, 0.9999983, 1.0000001, 1.0000031, 1.00000297],
+                  [0.9999995, 1.0000003, 1.0000005, 1.0000001, 1.00000032],
+                  [0.9999999, 0.9999997, 0.9999994, 0.9999989, 0.99999786],
+                  [0.9999999, 0.9999999, 0.9999999, 0.9999999, 0.99999991]]
+        # Get iteration points
+        grad_list = [prob.grad(x) for x in x_list]
+        delta_x = [np.array(x_list[i+1])-np.array(x_list[i])
+                   for i in range(len(x_list)-1)]
+        delta_grad = [grad_list[i+1]-grad_list[i]
+                      for i in range(len(grad_list)-1)]
+        # Check curvature condition
+        for s, y in zip(delta_x, delta_grad):
+            if np.dot(s, y) <= 0:
+                raise ArithmeticError()
+        # Define QuasiNewton update
+        for quasi_newton in (BFGS(init_scale=1, min_curvature=1e-4),
+                             SR1(init_scale=1)):
+            hess = deepcopy(quasi_newton)
+            inv_hess = deepcopy(quasi_newton)
+            hess.initialize(len(x_list[0]), 'hess')
+            inv_hess.initialize(len(x_list[0]), 'inv_hess')
+            # Compare the hessian and its inverse
+            for s, y in zip(delta_x, delta_grad):
+                hess.update(s, y)
+                inv_hess.update(s, y)
+                B = hess.get_matrix()
+                H = inv_hess.get_matrix()
+                assert_array_almost_equal(np.linalg.inv(B), H, decimal=10)
+            B_true = prob.hess(x_list[len(delta_x)])
+            assert_array_less(norm(B - B_true)/norm(B_true), 0.1)
+
+    def test_SR1_skip_update(self):
+        # Define auxiliary problem
+        prob = Rosenbrock(n=5)
+        # Define iteration points
+        x_list = [[0.0976270, 0.4303787, 0.2055267, 0.0897663, -0.15269040],
+                  [0.1847239, 0.0505757, 0.2123832, 0.0255081, 0.00083286],
+                  [0.2142498, -0.0188480, 0.0503822, 0.0347033, 0.03323606],
+                  [0.2071680, -0.0185071, 0.0341337, -0.0139298, 0.02881750],
+                  [0.1533055, -0.0322935, 0.0280418, -0.0083592, 0.01503699],
+                  [0.1382378, -0.0276671, 0.0266161, -0.0074060, 0.02801610],
+                  [0.1651957, -0.0049124, 0.0269665, -0.0040025, 0.02138184],
+                  [0.2354930, 0.0443711, 0.0173959, 0.0041872, 0.00794563],
+                  [0.4168118, 0.1433867, 0.0111714, 0.0126265, -0.00658537],
+                  [0.4681972, 0.2153273, 0.0225249, 0.0152704, -0.00463809],
+                  [0.6023068, 0.3346815, 0.0731108, 0.0186618, -0.00371541],
+                  [0.6415743, 0.3985468, 0.1324422, 0.0214160, -0.00062401],
+                  [0.7503690, 0.5447616, 0.2804541, 0.0539851, 0.00242230],
+                  [0.7452626, 0.5644594, 0.3324679, 0.0865153, 0.00454960],
+                  [0.8059782, 0.6586838, 0.4229577, 0.1452990, 0.00976702],
+                  [0.8549542, 0.7226562, 0.4991309, 0.2420093, 0.02772661],
+                  [0.8571332, 0.7285741, 0.5279076, 0.2824549, 0.06030276],
+                  [0.8835633, 0.7727077, 0.5957984, 0.3411303, 0.09652185],
+                  [0.9071558, 0.8299587, 0.6771400, 0.4402896, 0.17469338]]
+        # Get iteration points
+        grad_list = [prob.grad(x) for x in x_list]
+        delta_x = [np.array(x_list[i+1])-np.array(x_list[i])
+                   for i in range(len(x_list)-1)]
+        delta_grad = [grad_list[i+1]-grad_list[i]
+                      for i in range(len(grad_list)-1)]
+        hess = SR1(init_scale=1, min_denominator=1e-2)
+        hess.initialize(len(x_list[0]), 'hess')
+        # Compare the Hessian and its inverse
+        for i in range(len(delta_x)-1):
+            s = delta_x[i]
+            y = delta_grad[i]
+            hess.update(s, y)
+        # Test skip update
+        B = np.copy(hess.get_matrix())
+        s = delta_x[17]
+        y = delta_grad[17]
+        hess.update(s, y)
+        B_updated = np.copy(hess.get_matrix())
+        assert_array_equal(B, B_updated)
+
+    def test_BFGS_skip_update(self):
+        # Define auxiliary problem
+        prob = Rosenbrock(n=5)
+        # Define iteration points
+        x_list = [[0.0976270, 0.4303787, 0.2055267, 0.0897663, -0.15269040],
+                  [0.1847239, 0.0505757, 0.2123832, 0.0255081, 0.00083286],
+                  [0.2142498, -0.0188480, 0.0503822, 0.0347033, 0.03323606],
+                  [0.2071680, -0.0185071, 0.0341337, -0.0139298, 0.02881750],
+                  [0.1533055, -0.0322935, 0.0280418, -0.0083592, 0.01503699],
+                  [0.1382378, -0.0276671, 0.0266161, -0.0074060, 0.02801610],
+                  [0.1651957, -0.0049124, 0.0269665, -0.0040025, 0.02138184]]
+        # Get iteration points
+        grad_list = [prob.grad(x) for x in x_list]
+        delta_x = [np.array(x_list[i+1])-np.array(x_list[i])
+                   for i in range(len(x_list)-1)]
+        delta_grad = [grad_list[i+1]-grad_list[i]
+                      for i in range(len(grad_list)-1)]
+        hess = BFGS(init_scale=1, min_curvature=10)
+        hess.initialize(len(x_list[0]), 'hess')
+        # Compare the Hessian and its inverse
+        for i in range(len(delta_x)-1):
+            s = delta_x[i]
+            y = delta_grad[i]
+            hess.update(s, y)
+        # Test skip update
+        B = np.copy(hess.get_matrix())
+        s = delta_x[5]
+        y = delta_grad[5]
+        hess.update(s, y)
+        B_updated = np.copy(hess.get_matrix())
+        assert_array_equal(B, B_updated)
+
+
+@pytest.mark.parametrize('strategy', [BFGS, SR1])
+@pytest.mark.parametrize('approx_type', ['hess', 'inv_hess'])
+def test_matmul_equals_dot(strategy, approx_type):
+    H = strategy(init_scale=1)
+    H.initialize(2, approx_type)
+    v = np.array([1, 2])
+    assert_array_equal(H @ v, H.dot(v))

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_isotonic_regression.py

@@ -0,0 +1,167 @@
+import numpy as np
+from numpy.testing import assert_allclose, assert_equal
+import pytest
+
+from scipy.optimize._pava_pybind import pava
+from scipy.optimize import isotonic_regression
+
+
+class TestIsotonicRegression:
+    @pytest.mark.parametrize(
+        ("y", "w", "msg"),
+        [
+            ([[0, 1]], None,
+             "array has incorrect number of dimensions: 2; expected 1"),
+            ([0, 1], [[1, 2]],
+             "Input arrays y and w must have one dimension of equal length"),
+            ([0, 1], [1],
+             "Input arrays y and w must have one dimension of equal length"),
+            (1, [1, 2],
+             "Input arrays y and w must have one dimension of equal length"),
+            ([1, 2], 1,
+             "Input arrays y and w must have one dimension of equal length"),
+            ([0, 1], [0, 1],
+             "Weights w must be strictly positive"),
+        ]
+    )
+    def test_raise_error(self, y, w, msg):
+        with pytest.raises(ValueError, match=msg):
+            isotonic_regression(y=y, weights=w)
+
+    def test_simple_pava(self):
+        # Test case of Busing 2020
+        # https://doi.org/10.18637/jss.v102.c01
+        y = np.array([8, 4, 8, 2, 2, 0, 8], dtype=np.float64)
+        w = np.ones_like(y)
+        r = np.full(shape=y.shape[0] + 1, fill_value=-1, dtype=np.intp)
+        pava(y, w, r)
+        assert_allclose(y, [4, 4, 4, 4, 4, 4, 8])
+        # Only first 2 elements of w are changed.
+        assert_allclose(w, [6, 1, 1, 1, 1, 1, 1])
+        # Only first 3 elements of r are changed.
+        assert_allclose(r, [0, 6, 7, -1, -1, -1, -1, -1])
+
+    @pytest.mark.parametrize("y_dtype", [np.float64, np.float32, np.int64, np.int32])
+    @pytest.mark.parametrize("w_dtype", [np.float64, np.float32, np.int64, np.int32])
+    @pytest.mark.parametrize("w", [None, "ones"])
+    def test_simple_isotonic_regression(self, w, w_dtype, y_dtype):
+        # Test case of Busing 2020
+        # https://doi.org/10.18637/jss.v102.c01
+        y = np.array([8, 4, 8, 2, 2, 0, 8], dtype=y_dtype)
+        if w is not None:
+            w = np.ones_like(y, dtype=w_dtype)
+        res = isotonic_regression(y, weights=w)
+        assert res.x.dtype == np.float64
+        assert res.weights.dtype == np.float64
+        assert_allclose(res.x, [4, 4, 4, 4, 4, 4, 8])
+        assert_allclose(res.weights, [6, 1])
+        assert_allclose(res.blocks, [0, 6, 7])
+        # Assert that y was not overwritten
+        assert_equal(y, np.array([8, 4, 8, 2, 2, 0, 8], dtype=np.float64))
+
+    @pytest.mark.parametrize("increasing", [True, False])
+    def test_linspace(self, increasing):
+        n = 10
+        y = np.linspace(0, 1, n) if increasing else np.linspace(1, 0, n)
+        res = isotonic_regression(y, increasing=increasing)
+        assert_allclose(res.x, y)
+        assert_allclose(res.blocks, np.arange(n + 1))
+
+    def test_weights(self):
+        w = np.array([1, 2, 5, 0.5, 0.5, 0.5, 1, 3])
+        y = np.array([3, 2, 1, 10, 9, 8, 20, 10])
+        res = isotonic_regression(y, weights=w)
+        assert_allclose(res.x, [12/8, 12/8, 12/8, 9, 9, 9, 50/4, 50/4])
+        assert_allclose(res.weights, [8, 1.5, 4])
+        assert_allclose(res.blocks, [0, 3, 6, 8])
+
+        # weights are like repeated observations, we repeat the 3rd element 5
+        # times.
+        w2 = np.array([1, 2, 1, 1, 1, 1, 1, 0.5, 0.5, 0.5, 1, 3])
+        y2 = np.array([3, 2, 1, 1, 1, 1, 1, 10, 9, 8, 20, 10])
+        res2 = isotonic_regression(y2, weights=w2)
+        assert_allclose(np.diff(res2.x[0:7]), 0)
+        assert_allclose(res2.x[4:], res.x)
+        assert_allclose(res2.weights, res.weights)
+        assert_allclose(res2.blocks[1:] - 4, res.blocks[1:])
+
+    def test_against_R_monotone(self):
+        y = [0, 6, 8, 3, 5, 2, 1, 7, 9, 4]
+        res = isotonic_regression(y)
+        # R code
+        # library(monotone)
+        # options(digits=8)
+        # monotone(c(0, 6, 8, 3, 5, 2, 1, 7, 9, 4))
+        x_R = [
+            0, 4.1666667, 4.1666667, 4.1666667, 4.1666667, 4.1666667,
+            4.1666667, 6.6666667, 6.6666667, 6.6666667,
+        ]
+        assert_allclose(res.x, x_R)
+        assert_equal(res.blocks, [0, 1, 7, 10])
+
+        n = 100
+        y = np.linspace(0, 1, num=n, endpoint=False)
+        y = 5 * y + np.sin(10 * y)
+        res = isotonic_regression(y)
+        # R code
+        # library(monotone)
+        # n <- 100
+        # y <- 5 * ((1:n)-1)/n + sin(10 * ((1:n)-1)/n)
+        # options(digits=8)
+        # monotone(y)
+        x_R = [
+            0.00000000, 0.14983342, 0.29866933, 0.44552021, 0.58941834, 0.72942554,
+            0.86464247, 0.99421769, 1.11735609, 1.23332691, 1.34147098, 1.44120736,
+            1.53203909, 1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100,
+            1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100,
+            1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100,
+            1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100,
+            1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100,
+            1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100, 1.57081100,
+            1.57081100, 1.57081100, 1.57081100, 1.62418532, 1.71654534, 1.81773256,
+            1.92723551, 2.04445967, 2.16873336, 2.29931446, 2.43539782, 2.57612334,
+            2.72058450, 2.86783750, 3.01691060, 3.16681390, 3.31654920, 3.46511999,
+            3.61154136, 3.75484992, 3.89411335, 4.02843976, 4.15698660, 4.27896904,
+            4.39366786, 4.50043662, 4.59870810, 4.68799998, 4.76791967, 4.83816823,
+            4.86564130, 4.86564130, 4.86564130, 4.86564130, 4.86564130, 4.86564130,
+            4.86564130, 4.86564130, 4.86564130, 4.86564130, 4.86564130, 4.86564130,
+            4.86564130, 4.86564130, 4.86564130, 4.86564130, 4.86564130, 4.86564130,
+            4.86564130, 4.86564130, 4.86564130, 4.86564130,
+        ]
+        assert_allclose(res.x, x_R)
+
+        # Test increasing
+        assert np.all(np.diff(res.x) >= 0)
+
+        # Test balance property: sum(y) == sum(x)
+        assert_allclose(np.sum(res.x), np.sum(y))
+
+        # Reverse order
+        res_inv = isotonic_regression(-y, increasing=False)
+        assert_allclose(-res_inv.x, res.x)
+        assert_equal(res_inv.blocks, res.blocks)
+
+    def test_readonly(self):
+        x = np.arange(3, dtype=float)
+        w = np.ones(3, dtype=float)
+
+        x.flags.writeable = False
+        w.flags.writeable = False
+
+        res = isotonic_regression(x, weights=w)
+        assert np.all(np.isfinite(res.x))
+        assert np.all(np.isfinite(res.weights))
+        assert np.all(np.isfinite(res.blocks))
+
+    def test_non_contiguous_arrays(self):
+        x = np.arange(10, dtype=float)[::3]
+        w = np.ones(10, dtype=float)[::3]
+        assert not x.flags.c_contiguous
+        assert not x.flags.f_contiguous
+        assert not w.flags.c_contiguous
+        assert not w.flags.f_contiguous
+
+        res = isotonic_regression(x, weights=w)
+        assert np.all(np.isfinite(res.x))
+        assert np.all(np.isfinite(res.weights))
+        assert np.all(np.isfinite(res.blocks))

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_lbfgsb_hessinv.py

@@ -0,0 +1,65 @@
+import numpy as np
+from numpy.testing import assert_allclose
+import scipy.linalg
+from scipy.optimize import minimize
+
+
+def test_1():
+    def f(x):
+        return x**4, 4*x**3
+
+    for gtol in [1e-8, 1e-12, 1e-20]:
+        for maxcor in range(20, 35):
+            result = minimize(fun=f, jac=True, method='L-BFGS-B', x0=20,
+                options={'gtol': gtol, 'maxcor': maxcor})
+
+            H1 = result.hess_inv(np.array([1])).reshape(1,1)
+            H2 = result.hess_inv.todense()
+
+            assert_allclose(H1, H2)
+
+
+def test_2():
+    H0 = [[3, 0], [1, 2]]
+
+    def f(x):
+        return np.dot(x, np.dot(scipy.linalg.inv(H0), x))
+
+    result1 = minimize(fun=f, method='L-BFGS-B', x0=[10, 20])
+    result2 = minimize(fun=f, method='BFGS', x0=[10, 20])
+
+    H1 = result1.hess_inv.todense()
+
+    H2 = np.vstack((
+        result1.hess_inv(np.array([1, 0])),
+        result1.hess_inv(np.array([0, 1]))))
+
+    assert_allclose(
+        result1.hess_inv(np.array([1, 0]).reshape(2,1)).reshape(-1),
+        result1.hess_inv(np.array([1, 0])))
+    assert_allclose(H1, H2)
+    assert_allclose(H1, result2.hess_inv, rtol=1e-2, atol=0.03)
+
+
+def test_3():
+
+    def todense_old_impl(self):
+        s, y, n_corrs, rho = self.sk, self.yk, self.n_corrs, self.rho
+        I_arr = np.eye(*self.shape, dtype=self.dtype)
+        Hk = I_arr
+
+        for i in range(n_corrs):
+            A1 = I_arr - s[i][:, np.newaxis] * y[i][np.newaxis, :] * rho[i]
+            A2 = I_arr - y[i][:, np.newaxis] * s[i][np.newaxis, :] * rho[i]
+
+            Hk = np.dot(A1, np.dot(Hk, A2)) + (rho[i] * s[i][:, np.newaxis] *
+                                                        s[i][np.newaxis, :])
+        return Hk
+
+    H0 = [[3, 0], [1, 2]]
+
+    def f(x):
+        return np.dot(x, np.dot(scipy.linalg.inv(H0), x))
+
+    result1 = minimize(fun=f, method='L-BFGS-B', x0=[10, 20])
+    assert_allclose(result1.hess_inv.todense(), todense_old_impl(result1.hess_inv))

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_lbfgsb_setulb.py

@@ -0,0 +1,122 @@
+import numpy as np
+from scipy.optimize import _lbfgsb, minimize
+
+
+def objfun(x):
+    """simplified objective func to test lbfgsb bound violation"""
+    x0 = [0.8750000000000278,
+          0.7500000000000153,
+          0.9499999999999722,
+          0.8214285714285992,
+          0.6363636363636085]
+    x1 = [1.0, 0.0, 1.0, 0.0, 0.0]
+    x2 = [1.0,
+          0.0,
+          0.9889733043149325,
+          0.0,
+          0.026353554421041155]
+    x3 = [1.0,
+          0.0,
+          0.9889917442915558,
+          0.0,
+          0.020341986743231205]
+
+    f0 = 5163.647901211178
+    f1 = 5149.8181642072905
+    f2 = 5149.379332309634
+    f3 = 5149.374490771297
+
+    g0 = np.array([-0.5934820547965749,
+                   1.6251549718258351,
+                   -71.99168459202559,
+                   5.346636965797545,
+                   37.10732723092604])
+    g1 = np.array([-0.43295349282641515,
+                   1.008607936794592,
+                   18.223666726602975,
+                   31.927010036981997,
+                   -19.667512518739386])
+    g2 = np.array([-0.4699874455100256,
+                   0.9466285353668347,
+                   -0.016874360242016825,
+                   48.44999161133457,
+                   5.819631620590712])
+    g3 = np.array([-0.46970678696829116,
+                   0.9612719312174818,
+                   0.006129809488833699,
+                   48.43557729419473,
+                   6.005481418498221])
+
+    if np.allclose(x, x0):
+        f = f0
+        g = g0
+    elif np.allclose(x, x1):
+        f = f1
+        g = g1
+    elif np.allclose(x, x2):
+        f = f2
+        g = g2
+    elif np.allclose(x, x3):
+        f = f3
+        g = g3
+    else:
+        raise ValueError(
+            'Simplified objective function not defined '
+            'at requested point')
+    return (np.copy(f), np.copy(g))
+
+
+def test_setulb_floatround():
+    """test if setulb() violates bounds
+
+    checks for violation due to floating point rounding error
+    """
+
+    n = 5
+    m = 10
+    factr = 1e7
+    pgtol = 1e-5
+    maxls = 20
+    nbd = np.full(shape=(n,), fill_value=2, dtype=np.int32)
+    low_bnd = np.zeros(n, dtype=np.float64)
+    upper_bnd = np.ones(n, dtype=np.float64)
+
+    x0 = np.array(
+        [0.8750000000000278,
+         0.7500000000000153,
+         0.9499999999999722,
+         0.8214285714285992,
+         0.6363636363636085])
+    x = np.copy(x0)
+
+    f = np.array(0.0, dtype=np.float64)
+    g = np.zeros(n, dtype=np.float64)
+
+    wa = np.zeros(2*m*n + 5*n + 11*m*m + 8*m, dtype=np.float64)
+    iwa = np.zeros(3*n, dtype=np.int32)
+    task = np.zeros(2, dtype=np.int32)
+    ln_task = np.zeros(2, dtype=np.int32)
+    lsave = np.zeros(4, dtype=np.int32)
+    isave = np.zeros(44, dtype=np.int32)
+    dsave = np.zeros(29, dtype=np.float64)
+
+    for n_iter in range(7):  # 7 steps required to reproduce error
+        f, g = objfun(x)
+
+        _lbfgsb.setulb(m, x, low_bnd, upper_bnd, nbd, f, g, factr, pgtol, wa,
+                       iwa, task, lsave, isave, dsave, maxls, ln_task)
+
+        assert (x <= upper_bnd).all() and (x >= low_bnd).all(), (
+            "_lbfgsb.setulb() stepped to a point outside of the bounds")
+
+
+def test_gh_issue18730():
+    # issue 18730 reported that l-bfgs-b did not work with objectives
+    # returning single precision gradient arrays
+    def fun_single_precision(x):
+        x = x.astype(np.float32)
+        return np.sum(x**2), (2*x)
+
+    res = minimize(fun_single_precision, x0=np.array([1., 1.]), jac=True,
+                   method="l-bfgs-b")
+    np.testing.assert_allclose(res.fun, 0., atol=1e-15)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_least_squares.py

@@ -0,0 +1,986 @@
+from itertools import product
+from multiprocessing import Pool
+
+import numpy as np
+from numpy.linalg import norm
+from numpy.testing import (assert_, assert_allclose,
+                           assert_equal, suppress_warnings)
+import pytest
+from pytest import raises as assert_raises
+from scipy.sparse import issparse, lil_array
+from scipy.sparse.linalg import aslinearoperator
+
+from scipy.optimize import least_squares, Bounds
+from scipy.optimize._lsq.least_squares import IMPLEMENTED_LOSSES
+from scipy.optimize._lsq.common import EPS, make_strictly_feasible, CL_scaling_vector
+
+from scipy.optimize import OptimizeResult
+
+def fun_trivial(x, a=0):
+    return (x - a)**2 + 5.0
+
+
+def jac_trivial(x, a=0.0):
+    return 2 * (x - a)
+
+
+def fun_2d_trivial(x):
+    return np.array([x[0], x[1]])
+
+
+def jac_2d_trivial(x):
+    return np.identity(2)
+
+
+def fun_rosenbrock(x):
+    return np.array([10 * (x[1] - x[0]**2), (1 - x[0])])
+
+
+class Fun_Rosenbrock:
+    def __init__(self):
+        self.nfev = 0
+
+    def __call__(self, x, a=0):
+        self.nfev += 1
+        return fun_rosenbrock(x)
+
+
+def jac_rosenbrock(x):
+    return np.array([
+        [-20 * x[0], 10],
+        [-1, 0]
+    ])
+
+
+def jac_rosenbrock_bad_dim(x):
+    return np.array([
+        [-20 * x[0], 10],
+        [-1, 0],
+        [0.0, 0.0]
+    ])
+
+
+def fun_rosenbrock_cropped(x):
+    return fun_rosenbrock(x)[0]
+
+
+def jac_rosenbrock_cropped(x):
+    return jac_rosenbrock(x)[0]
+
+
+# When x is 1-D array, return is 2-D array.
+def fun_wrong_dimensions(x):
+    return np.array([x, x**2, x**3])
+
+
+def jac_wrong_dimensions(x, a=0.0):
+    return np.atleast_3d(jac_trivial(x, a=a))
+
+
+def fun_bvp(x):
+    n = int(np.sqrt(x.shape[0]))
+    u = np.zeros((n + 2, n + 2))
+    x = x.reshape((n, n))
+    u[1:-1, 1:-1] = x
+    y = u[:-2, 1:-1] + u[2:, 1:-1] + u[1:-1, :-2] + u[1:-1, 2:] - 4 * x + x**3
+    return y.ravel()
+
+
+class BroydenTridiagonal:
+    def __init__(self, n=100, mode='sparse'):
+        rng = np.random.RandomState(0)
+
+        self.n = n
+
+        self.x0 = -np.ones(n)
+        self.lb = np.linspace(-2, -1.5, n)
+        self.ub = np.linspace(-0.8, 0.0, n)
+
+        self.lb += 0.1 * rng.randn(n)
+        self.ub += 0.1 * rng.randn(n)
+
+        self.x0 += 0.1 * rng.randn(n)
+        self.x0 = make_strictly_feasible(self.x0, self.lb, self.ub)
+
+        if mode == 'sparse':
+            self.sparsity = lil_array((n, n), dtype=int)
+            i = np.arange(n)
+            self.sparsity[i, i] = 1
+            i = np.arange(1, n)
+            self.sparsity[i, i - 1] = 1
+            i = np.arange(n - 1)
+            self.sparsity[i, i + 1] = 1
+
+            self.jac = self._jac
+        elif mode == 'operator':
+            self.jac = lambda x: aslinearoperator(self._jac(x))
+        elif mode == 'dense':
+            self.sparsity = None
+            self.jac = lambda x: self._jac(x).toarray()
+        else:
+            assert_(False)
+
+    def fun(self, x):
+        f = (3 - x) * x + 1
+        f[1:] -= x[:-1]
+        f[:-1] -= 2 * x[1:]
+        return f
+
+    def _jac(self, x):
+        J = lil_array((self.n, self.n))
+        i = np.arange(self.n)
+        J[i, i] = 3 - 2 * x
+        i = np.arange(1, self.n)
+        J[i, i - 1] = -1
+        i = np.arange(self.n - 1)
+        J[i, i + 1] = -2
+        return J
+
+
+class ExponentialFittingProblem:
+    """Provide data and function for exponential fitting in the form
+    y = a + exp(b * x) + noise."""
+
+    def __init__(self, a, b, noise, n_outliers=1, x_range=(-1, 1),
+                 n_points=11, random_seed=None):
+        rng = np.random.RandomState(random_seed)
+        self.m = n_points
+        self.n = 2
+
+        self.p0 = np.zeros(2)
+        self.x = np.linspace(x_range[0], x_range[1], n_points)
+
+        self.y = a + np.exp(b * self.x)
+        self.y += noise * rng.randn(self.m)
+
+        outliers = rng.randint(0, self.m, n_outliers)
+        self.y[outliers] += 50 * noise * rng.rand(n_outliers)
+
+        self.p_opt = np.array([a, b])
+
+    def fun(self, p):
+        return p[0] + np.exp(p[1] * self.x) - self.y
+
+    def jac(self, p):
+        J = np.empty((self.m, self.n))
+        J[:, 0] = 1
+        J[:, 1] = self.x * np.exp(p[1] * self.x)
+        return J
+
+
+def cubic_soft_l1(z):
+    rho = np.empty((3, z.size))
+
+    t = 1 + z
+    rho[0] = 3 * (t**(1/3) - 1)
+    rho[1] = t ** (-2/3)
+    rho[2] = -2/3 * t**(-5/3)
+
+    return rho
+
+
+LOSSES = list(IMPLEMENTED_LOSSES.keys()) + [cubic_soft_l1]
+
+
+class BaseMixin:
+    def test_basic(self):
+        # Test that the basic calling sequence works.
+        res = least_squares(fun_trivial, 2., method=self.method)
+        assert_allclose(res.x, 0, atol=1e-4)
+        assert_allclose(res.fun, fun_trivial(res.x))
+
+    def test_args_kwargs(self):
+        # Test that args and kwargs are passed correctly to the functions.
+        a = 3.0
+        for jac in ['2-point', '3-point', 'cs', jac_trivial]:
+            with suppress_warnings() as sup:
+                sup.filter(
+                    UserWarning,
+                    "jac='(3-point|cs)' works equivalently to '2-point' for method='lm'"
+                )
+                res = least_squares(fun_trivial, 2.0, jac, args=(a,),
+                                    method=self.method)
+                res1 = least_squares(fun_trivial, 2.0, jac, kwargs={'a': a},
+                                    method=self.method)
+
+            assert_allclose(res.x, a, rtol=1e-4)
+            assert_allclose(res1.x, a, rtol=1e-4)
+
+            assert_raises(TypeError, least_squares, fun_trivial, 2.0,
+                          args=(3, 4,), method=self.method)
+            assert_raises(TypeError, least_squares, fun_trivial, 2.0,
+                          kwargs={'kaboom': 3}, method=self.method)
+
+    def test_jac_options(self):
+        for jac in ['2-point', '3-point', 'cs', jac_trivial]:
+            with suppress_warnings() as sup:
+                sup.filter(
+                    UserWarning,
+                    "jac='(3-point|cs)' works equivalently to '2-point' for method='lm'"
+                )
+                res = least_squares(fun_trivial, 2.0, jac, method=self.method)
+            assert_allclose(res.x, 0, atol=1e-4)
+
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0, jac='oops',
+                      method=self.method)
+
+    def test_nfev_options(self):
+        for max_nfev in [None, 20]:
+            res = least_squares(fun_trivial, 2.0, max_nfev=max_nfev,
+                                method=self.method)
+            assert_allclose(res.x, 0, atol=1e-4)
+
+    def test_x_scale_options(self):
+        for x_scale in [1.0, np.array([0.5]), 'jac']:
+            res = least_squares(fun_trivial, 2.0, x_scale=x_scale)
+            assert_allclose(res.x, 0)
+        assert_raises(ValueError, least_squares, fun_trivial,
+                      2.0, x_scale='auto', method=self.method)
+        assert_raises(ValueError, least_squares, fun_trivial,
+                      2.0, x_scale=-1.0, method=self.method)
+        assert_raises(ValueError, least_squares, fun_trivial,
+                      2.0, x_scale=1.0+2.0j, method=self.method)
+
+    def test_diff_step(self):
+        res1 = least_squares(fun_trivial, 2.0, diff_step=1e-1,
+                             method=self.method)
+        res3 = least_squares(fun_trivial, 2.0,
+                             diff_step=None, method=self.method)
+        assert_allclose(res1.x, 0, atol=1e-4)
+        assert_allclose(res3.x, 0, atol=1e-4)
+
+
+    def test_incorrect_options_usage(self):
+        assert_raises(TypeError, least_squares, fun_trivial, 2.0,
+                      method=self.method, options={'no_such_option': 100})
+        assert_raises(TypeError, least_squares, fun_trivial, 2.0,
+                      method=self.method, options={'max_nfev': 100})
+
+    def test_full_result(self):
+        # MINPACK doesn't work very well with factor=100 on this problem,
+        # thus using low 'atol'.
+        res = least_squares(fun_trivial, 2.0, method=self.method)
+        assert_allclose(res.x, 0, atol=1e-4)
+        assert_allclose(res.cost, 12.5)
+        assert_allclose(res.fun, 5)
+        assert_allclose(res.jac, 0, atol=1e-4)
+        assert_allclose(res.grad, 0, atol=1e-2)
+        assert_allclose(res.optimality, 0, atol=1e-2)
+        assert_equal(res.active_mask, 0)
+        if self.method == 'lm':
+            assert_(res.njev is None)
+        else:
+            assert_(res.nfev < 10)
+            assert_(res.njev < 10)
+        assert_(res.status > 0)
+        assert_(res.success)
+
+    def test_full_result_single_fev(self):
+        # MINPACK checks the number of nfev after the iteration,
+        # so it's hard to tell what he is going to compute.
+        if self.method == 'lm':
+            return
+
+        res = least_squares(fun_trivial, 2.0, method=self.method,
+                            max_nfev=1)
+        assert_equal(res.x, np.array([2]))
+        assert_equal(res.cost, 40.5)
+        assert_equal(res.fun, np.array([9]))
+        assert_equal(res.jac, np.array([[4]]))
+        assert_equal(res.grad, np.array([36]))
+        assert_equal(res.optimality, 36)
+        assert_equal(res.active_mask, np.array([0]))
+        assert_equal(res.nfev, 1)
+        assert_equal(res.njev, 1)
+        assert_equal(res.status, 0)
+        assert_equal(res.success, 0)
+
+    def test_nfev(self):
+        # checks that the true number of nfev are being consumed
+        for i in range(1, 3):
+            rng = np.random.default_rng(128908)
+            x0 = rng.uniform(size=2) * 10
+            ftrivial = Fun_Rosenbrock()
+            res = least_squares(
+               ftrivial, x0, jac=jac_rosenbrock, method=self.method, max_nfev=i
+            )
+            assert res.nfev == ftrivial.nfev
+
+    def test_rosenbrock(self):
+        x0 = [-2, 1]
+        x_opt = [1, 1]
+        for jac, x_scale, tr_solver in product(
+                ['2-point', '3-point', 'cs', jac_rosenbrock],
+                [1.0, np.array([1.0, 0.2]), 'jac'],
+                ['exact', 'lsmr']):
+            with suppress_warnings() as sup:
+                sup.filter(
+                    UserWarning,
+                    "jac='(3-point|cs)' works equivalently to '2-point' for method='lm'"
+                )
+                res = least_squares(fun_rosenbrock, x0, jac, x_scale=x_scale,
+                                    tr_solver=tr_solver, method=self.method)
+            assert_allclose(res.x, x_opt)
+
+    def test_rosenbrock_cropped(self):
+        x0 = [-2, 1]
+        if self.method == 'lm':
+            assert_raises(ValueError, least_squares, fun_rosenbrock_cropped,
+                          x0, method='lm')
+        else:
+            for jac, x_scale, tr_solver in product(
+                    ['2-point', '3-point', 'cs', jac_rosenbrock_cropped],
+                    [1.0, np.array([1.0, 0.2]), 'jac'],
+                    ['exact', 'lsmr']):
+                res = least_squares(
+                    fun_rosenbrock_cropped, x0, jac, x_scale=x_scale,
+                    tr_solver=tr_solver, method=self.method)
+                assert_allclose(res.cost, 0, atol=1e-14)
+
+    def test_fun_wrong_dimensions(self):
+        assert_raises(ValueError, least_squares, fun_wrong_dimensions,
+                      2.0, method=self.method)
+
+    def test_jac_wrong_dimensions(self):
+        assert_raises(ValueError, least_squares, fun_trivial,
+                      2.0, jac_wrong_dimensions, method=self.method)
+
+    def test_fun_and_jac_inconsistent_dimensions(self):
+        x0 = [1, 2]
+        assert_raises(ValueError, least_squares, fun_rosenbrock, x0,
+                      jac_rosenbrock_bad_dim, method=self.method)
+
+    def test_x0_multidimensional(self):
+        x0 = np.ones(4).reshape(2, 2)
+        assert_raises(ValueError, least_squares, fun_trivial, x0,
+                      method=self.method)
+
+    def test_x0_complex_scalar(self):
+        x0 = 2.0 + 0.0*1j
+        assert_raises(ValueError, least_squares, fun_trivial, x0,
+                      method=self.method)
+
+    def test_x0_complex_array(self):
+        x0 = [1.0, 2.0 + 0.0*1j]
+        assert_raises(ValueError, least_squares, fun_trivial, x0,
+                      method=self.method)
+
+    def test_bvp(self):
+        # This test was introduced with fix #5556. It turned out that
+        # dogbox solver had a bug with trust-region radius update, which
+        # could block its progress and create an infinite loop. And this
+        # discrete boundary value problem is the one which triggers it.
+        n = 10
+        x0 = np.ones(n**2)
+        if self.method == 'lm':
+            max_nfev = 5000  # To account for Jacobian estimation.
+        else:
+            max_nfev = 100
+        res = least_squares(fun_bvp, x0, ftol=1e-2, method=self.method,
+                            max_nfev=max_nfev)
+
+        assert_(res.nfev < max_nfev)
+        assert_(res.cost < 0.5)
+
+    def test_error_raised_when_all_tolerances_below_eps(self):
+        # Test that all 0 tolerances are not allowed.
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0,
+                      method=self.method, ftol=None, xtol=None, gtol=None)
+
+    def test_convergence_with_only_one_tolerance_enabled(self):
+        if self.method == 'lm':
+            return  # should not do test
+        x0 = [-2, 1]
+        x_opt = [1, 1]
+        for ftol, xtol, gtol in [(1e-8, None, None),
+                                  (None, 1e-8, None),
+                                  (None, None, 1e-8)]:
+            res = least_squares(fun_rosenbrock, x0, jac=jac_rosenbrock,
+                                ftol=ftol, gtol=gtol, xtol=xtol,
+                                method=self.method)
+            assert_allclose(res.x, x_opt)
+
+    @pytest.mark.fail_slow(5.0)
+    def test_workers(self):
+        serial = least_squares(fun_trivial, 2.0, method=self.method)
+
+        reses = []
+        for workers in [None, 2]:
+            res = least_squares(
+                fun_trivial, 2.0, method=self.method, workers=workers
+            )
+            reses.append(res)
+        with Pool() as workers:
+            res = least_squares(
+                fun_trivial, 2.0, method=self.method, workers=workers.map
+            )
+            reses.append(res)
+        for res in reses:
+            assert res.success
+            assert_equal(res.x, serial.x)
+            assert_equal(res.nfev, serial.nfev)
+            assert_equal(res.njev, serial.njev)
+
+
+class BoundsMixin:
+    def test_inconsistent(self):
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0,
+                      bounds=(10.0, 0.0), method=self.method)
+
+    def test_infeasible(self):
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0,
+                      bounds=(3., 4), method=self.method)
+
+    def test_wrong_number(self):
+        assert_raises(ValueError, least_squares, fun_trivial, 2.,
+                      bounds=(1., 2, 3), method=self.method)
+
+    def test_inconsistent_shape(self):
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0,
+                      bounds=(1.0, [2.0, 3.0]), method=self.method)
+        # 1-D array won't be broadcast
+        assert_raises(ValueError, least_squares, fun_rosenbrock, [1.0, 2.0],
+                      bounds=([0.0], [3.0, 4.0]), method=self.method)
+
+    def test_in_bounds(self):
+        for jac in ['2-point', '3-point', 'cs', jac_trivial]:
+            res = least_squares(fun_trivial, 2.0, jac=jac,
+                                bounds=(-1.0, 3.0), method=self.method)
+            assert_allclose(res.x, 0.0, atol=1e-4)
+            assert_equal(res.active_mask, [0])
+            assert_(-1 <= res.x <= 3)
+            res = least_squares(fun_trivial, 2.0, jac=jac,
+                                bounds=(0.5, 3.0), method=self.method)
+            assert_allclose(res.x, 0.5, atol=1e-4)
+            assert_equal(res.active_mask, [-1])
+            assert_(0.5 <= res.x <= 3)
+
+    def test_bounds_shape(self):
+        def get_bounds_direct(lb, ub):
+            return lb, ub
+
+        def get_bounds_instances(lb, ub):
+            return Bounds(lb, ub)
+
+        for jac in ['2-point', '3-point', 'cs', jac_2d_trivial]:
+            for bounds_func in [get_bounds_direct, get_bounds_instances]:
+                x0 = [1.0, 1.0]
+                res = least_squares(fun_2d_trivial, x0, jac=jac)
+                assert_allclose(res.x, [0.0, 0.0])
+                res = least_squares(fun_2d_trivial, x0, jac=jac,
+                                    bounds=bounds_func(0.5, [2.0, 2.0]),
+                                    method=self.method)
+                assert_allclose(res.x, [0.5, 0.5])
+                res = least_squares(fun_2d_trivial, x0, jac=jac,
+                                    bounds=bounds_func([0.3, 0.2], 3.0),
+                                    method=self.method)
+                assert_allclose(res.x, [0.3, 0.2])
+                res = least_squares(
+                    fun_2d_trivial, x0, jac=jac,
+                    bounds=bounds_func([-1, 0.5], [1.0, 3.0]),
+                    method=self.method)
+                assert_allclose(res.x, [0.0, 0.5], atol=1e-5)
+
+    def test_bounds_instances(self):
+        res = least_squares(fun_trivial, 0.5, bounds=Bounds())
+        assert_allclose(res.x, 0.0, atol=1e-4)
+
+        res = least_squares(fun_trivial, 3.0, bounds=Bounds(lb=1.0))
+        assert_allclose(res.x, 1.0, atol=1e-4)
+
+        res = least_squares(fun_trivial, 0.5, bounds=Bounds(lb=-1.0, ub=1.0))
+        assert_allclose(res.x, 0.0, atol=1e-4)
+
+        res = least_squares(fun_trivial, -3.0, bounds=Bounds(ub=-1.0))
+        assert_allclose(res.x, -1.0, atol=1e-4)
+
+        res = least_squares(fun_2d_trivial, [0.5, 0.5],
+                            bounds=Bounds(lb=[-1.0, -1.0], ub=1.0))
+        assert_allclose(res.x, [0.0, 0.0], atol=1e-5)
+
+        res = least_squares(fun_2d_trivial, [0.5, 0.5],
+                            bounds=Bounds(lb=[0.1, 0.1]))
+        assert_allclose(res.x, [0.1, 0.1], atol=1e-5)
+
+    @pytest.mark.fail_slow(10)
+    def test_rosenbrock_bounds(self):
+        x0_1 = np.array([-2.0, 1.0])
+        x0_2 = np.array([2.0, 2.0])
+        x0_3 = np.array([-2.0, 2.0])
+        x0_4 = np.array([0.0, 2.0])
+        x0_5 = np.array([-1.2, 1.0])
+        problems = [
+            (x0_1, ([-np.inf, -1.5], np.inf)),
+            (x0_2, ([-np.inf, 1.5], np.inf)),
+            (x0_3, ([-np.inf, 1.5], np.inf)),
+            (x0_4, ([-np.inf, 1.5], [1.0, np.inf])),
+            (x0_2, ([1.0, 1.5], [3.0, 3.0])),
+            (x0_5, ([-50.0, 0.0], [0.5, 100]))
+        ]
+        for x0, bounds in problems:
+            for jac, x_scale, tr_solver in product(
+                    ['2-point', '3-point', 'cs', jac_rosenbrock],
+                    [1.0, [1.0, 0.5], 'jac'],
+                    ['exact', 'lsmr']):
+                res = least_squares(fun_rosenbrock, x0, jac, bounds,
+                                    x_scale=x_scale, tr_solver=tr_solver,
+                                    method=self.method)
+                assert_allclose(res.optimality, 0.0, atol=1e-5)
+
+
+class SparseMixin:
+    def test_exact_tr_solver(self):
+        p = BroydenTridiagonal()
+        assert_raises(ValueError, least_squares, p.fun, p.x0, p.jac,
+                      tr_solver='exact', method=self.method)
+        assert_raises(ValueError, least_squares, p.fun, p.x0,
+                      tr_solver='exact', jac_sparsity=p.sparsity,
+                      method=self.method)
+
+    def test_equivalence(self):
+        sparse = BroydenTridiagonal(mode='sparse')
+        dense = BroydenTridiagonal(mode='dense')
+        res_sparse = least_squares(
+            sparse.fun, sparse.x0, jac=sparse.jac,
+            method=self.method)
+        res_dense = least_squares(
+            dense.fun, dense.x0, jac=sparse.jac,
+            method=self.method)
+        assert_equal(res_sparse.nfev, res_dense.nfev)
+        assert_allclose(res_sparse.x, res_dense.x, atol=1e-20)
+        assert_allclose(res_sparse.cost, 0, atol=1e-20)
+        assert_allclose(res_dense.cost, 0, atol=1e-20)
+
+    def test_tr_options(self):
+        p = BroydenTridiagonal()
+        res = least_squares(p.fun, p.x0, p.jac, method=self.method,
+                            tr_options={'btol': 1e-10})
+        assert_allclose(res.cost, 0, atol=1e-20)
+
+    def test_wrong_parameters(self):
+        p = BroydenTridiagonal()
+        assert_raises(ValueError, least_squares, p.fun, p.x0, p.jac,
+                      tr_solver='best', method=self.method)
+        assert_raises(TypeError, least_squares, p.fun, p.x0, p.jac,
+                      tr_solver='lsmr', tr_options={'tol': 1e-10})
+
+    def test_solver_selection(self):
+        sparse = BroydenTridiagonal(mode='sparse')
+        dense = BroydenTridiagonal(mode='dense')
+        res_sparse = least_squares(sparse.fun, sparse.x0, jac=sparse.jac,
+                                   method=self.method)
+        res_dense = least_squares(dense.fun, dense.x0, jac=dense.jac,
+                                  method=self.method)
+        assert_allclose(res_sparse.cost, 0, atol=1e-20)
+        assert_allclose(res_dense.cost, 0, atol=1e-20)
+        assert_(issparse(res_sparse.jac))
+        assert_(isinstance(res_dense.jac, np.ndarray))
+
+    def test_numerical_jac(self):
+        p = BroydenTridiagonal()
+        for jac in ['2-point', '3-point', 'cs']:
+            res_dense = least_squares(p.fun, p.x0, jac, method=self.method)
+            res_sparse = least_squares(
+                p.fun, p.x0, jac,method=self.method,
+                jac_sparsity=p.sparsity)
+            assert_equal(res_dense.nfev, res_sparse.nfev)
+            assert_allclose(res_dense.x, res_sparse.x, atol=1e-20)
+            assert_allclose(res_dense.cost, 0, atol=1e-20)
+            assert_allclose(res_sparse.cost, 0, atol=1e-20)
+
+    @pytest.mark.fail_slow(10)
+    def test_with_bounds(self):
+        p = BroydenTridiagonal()
+        for jac, jac_sparsity in product(
+                [p.jac, '2-point', '3-point', 'cs'], [None, p.sparsity]):
+            res_1 = least_squares(
+                p.fun, p.x0, jac, bounds=(p.lb, np.inf),
+                method=self.method,jac_sparsity=jac_sparsity)
+            res_2 = least_squares(
+                p.fun, p.x0, jac, bounds=(-np.inf, p.ub),
+                method=self.method, jac_sparsity=jac_sparsity)
+            res_3 = least_squares(
+                p.fun, p.x0, jac, bounds=(p.lb, p.ub),
+                method=self.method, jac_sparsity=jac_sparsity)
+            assert_allclose(res_1.optimality, 0, atol=1e-10)
+            assert_allclose(res_2.optimality, 0, atol=1e-10)
+            assert_allclose(res_3.optimality, 0, atol=1e-10)
+
+    def test_wrong_jac_sparsity(self):
+        p = BroydenTridiagonal()
+        sparsity = p.sparsity[:-1]
+        assert_raises(ValueError, least_squares, p.fun, p.x0,
+                      jac_sparsity=sparsity, method=self.method)
+
+    def test_linear_operator(self):
+        p = BroydenTridiagonal(mode='operator')
+        res = least_squares(p.fun, p.x0, p.jac, method=self.method)
+        assert_allclose(res.cost, 0.0, atol=1e-20)
+        assert_raises(ValueError, least_squares, p.fun, p.x0, p.jac,
+                      method=self.method, tr_solver='exact')
+
+    def test_x_scale_jac_scale(self):
+        p = BroydenTridiagonal()
+        res = least_squares(p.fun, p.x0, p.jac, method=self.method,
+                            x_scale='jac')
+        assert_allclose(res.cost, 0.0, atol=1e-20)
+
+        p = BroydenTridiagonal(mode='operator')
+        assert_raises(ValueError, least_squares, p.fun, p.x0, p.jac,
+                      method=self.method, x_scale='jac')
+
+
+class LossFunctionMixin:
+    def test_options(self):
+        for loss in LOSSES:
+            res = least_squares(fun_trivial, 2.0, loss=loss,
+                                method=self.method)
+            assert_allclose(res.x, 0, atol=1e-15)
+
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0,
+                      loss='hinge', method=self.method)
+
+    def test_fun(self):
+        # Test that res.fun is actual residuals, and not modified by loss
+        # function stuff.
+        for loss in LOSSES:
+            res = least_squares(fun_trivial, 2.0, loss=loss,
+                                method=self.method)
+            assert_equal(res.fun, fun_trivial(res.x))
+
+    def test_grad(self):
+        # Test that res.grad is true gradient of loss function at the
+        # solution. Use max_nfev = 1, to avoid reaching minimum.
+        x = np.array([2.0])  # res.x will be this.
+
+        res = least_squares(fun_trivial, x, jac_trivial, loss='linear',
+                            max_nfev=1, method=self.method)
+        assert_equal(res.grad, 2 * x * (x**2 + 5))
+
+        res = least_squares(fun_trivial, x, jac_trivial, loss='huber',
+                            max_nfev=1, method=self.method)
+        assert_equal(res.grad, 2 * x)
+
+        res = least_squares(fun_trivial, x, jac_trivial, loss='soft_l1',
+                            max_nfev=1, method=self.method)
+        assert_allclose(res.grad,
+                        2 * x * (x**2 + 5) / (1 + (x**2 + 5)**2)**0.5)
+
+        res = least_squares(fun_trivial, x, jac_trivial, loss='cauchy',
+                            max_nfev=1, method=self.method)
+        assert_allclose(res.grad, 2 * x * (x**2 + 5) / (1 + (x**2 + 5)**2))
+
+        res = least_squares(fun_trivial, x, jac_trivial, loss='arctan',
+                            max_nfev=1, method=self.method)
+        assert_allclose(res.grad, 2 * x * (x**2 + 5) / (1 + (x**2 + 5)**4))
+
+        res = least_squares(fun_trivial, x, jac_trivial, loss=cubic_soft_l1,
+                            max_nfev=1, method=self.method)
+        assert_allclose(res.grad,
+                        2 * x * (x**2 + 5) / (1 + (x**2 + 5)**2)**(2/3))
+
+    def test_jac(self):
+        # Test that res.jac.T.dot(res.jac) gives Gauss-Newton approximation
+        # of Hessian. This approximation is computed by doubly differentiating
+        # the cost function and dropping the part containing second derivative
+        # of f. For a scalar function it is computed as
+        # H = (rho' + 2 * rho'' * f**2) * f'**2, if the expression inside the
+        # brackets is less than EPS it is replaced by EPS. Here, we check
+        # against the root of H.
+
+        x = 2.0  # res.x will be this.
+        f = x**2 + 5  # res.fun will be this.
+
+        res = least_squares(fun_trivial, x, jac_trivial, loss='linear',
+                            max_nfev=1, method=self.method)
+        assert_equal(res.jac, 2 * x)
+
+        # For `huber` loss the Jacobian correction is identically zero
+        # in outlier region, in such cases it is modified to be equal EPS**0.5.
+        res = least_squares(fun_trivial, x, jac_trivial, loss='huber',
+                            max_nfev=1, method=self.method)
+        assert_equal(res.jac, 2 * x * EPS**0.5)
+
+        # Now, let's apply `loss_scale` to turn the residual into an inlier.
+        # The loss function becomes linear.
+        res = least_squares(fun_trivial, x, jac_trivial, loss='huber',
+                            f_scale=10, max_nfev=1)
+        assert_equal(res.jac, 2 * x)
+
+        # 'soft_l1' always gives a positive scaling.
+        res = least_squares(fun_trivial, x, jac_trivial, loss='soft_l1',
+                            max_nfev=1, method=self.method)
+        assert_allclose(res.jac, 2 * x * (1 + f**2)**-0.75)
+
+        # For 'cauchy' the correction term turns out to be negative, and it
+        # replaced by EPS**0.5.
+        res = least_squares(fun_trivial, x, jac_trivial, loss='cauchy',
+                            max_nfev=1, method=self.method)
+        assert_allclose(res.jac, 2 * x * EPS**0.5)
+
+        # Now use scaling to turn the residual to inlier.
+        res = least_squares(fun_trivial, x, jac_trivial, loss='cauchy',
+                            f_scale=10, max_nfev=1, method=self.method)
+        fs = f / 10
+        assert_allclose(res.jac, 2 * x * (1 - fs**2)**0.5 / (1 + fs**2))
+
+        # 'arctan' gives an outlier.
+        res = least_squares(fun_trivial, x, jac_trivial, loss='arctan',
+                            max_nfev=1, method=self.method)
+        assert_allclose(res.jac, 2 * x * EPS**0.5)
+
+        # Turn to inlier.
+        res = least_squares(fun_trivial, x, jac_trivial, loss='arctan',
+                            f_scale=20.0, max_nfev=1, method=self.method)
+        fs = f / 20
+        assert_allclose(res.jac, 2 * x * (1 - 3 * fs**4)**0.5 / (1 + fs**4))
+
+        # cubic_soft_l1 will give an outlier.
+        res = least_squares(fun_trivial, x, jac_trivial, loss=cubic_soft_l1,
+                            max_nfev=1)
+        assert_allclose(res.jac, 2 * x * EPS**0.5)
+
+        # Turn to inlier.
+        res = least_squares(fun_trivial, x, jac_trivial,
+                            loss=cubic_soft_l1, f_scale=6, max_nfev=1)
+        fs = f / 6
+        assert_allclose(res.jac,
+                        2 * x * (1 - fs**2 / 3)**0.5 * (1 + fs**2)**(-5/6))
+
+    def test_robustness(self):
+        for noise in [0.1, 1.0]:
+            p = ExponentialFittingProblem(1, 0.1, noise, random_seed=0)
+
+            for jac in ['2-point', '3-point', 'cs', p.jac]:
+                res_lsq = least_squares(p.fun, p.p0, jac=jac,
+                                        method=self.method)
+                assert_allclose(res_lsq.optimality, 0, atol=1e-2)
+                for loss in LOSSES:
+                    if loss == 'linear':
+                        continue
+                    res_robust = least_squares(
+                        p.fun, p.p0, jac=jac, loss=loss, f_scale=noise,
+                        method=self.method)
+                    assert_allclose(res_robust.optimality, 0, atol=1e-2)
+                    assert_(norm(res_robust.x - p.p_opt) <
+                            norm(res_lsq.x - p.p_opt))
+
+
+class TestDogbox(BaseMixin, BoundsMixin, SparseMixin, LossFunctionMixin):
+    method = 'dogbox'
+
+
+class TestTRF(BaseMixin, BoundsMixin, SparseMixin, LossFunctionMixin):
+    method = 'trf'
+
+    def test_lsmr_regularization(self):
+        p = BroydenTridiagonal()
+        for regularize in [True, False]:
+            res = least_squares(p.fun, p.x0, p.jac, method='trf',
+                                tr_options={'regularize': regularize})
+            assert_allclose(res.cost, 0, atol=1e-20)
+
+
+class TestLM(BaseMixin):
+    method = 'lm'
+
+    def test_bounds_not_supported(self):
+        assert_raises(ValueError, least_squares, fun_trivial,
+                      2.0, bounds=(-3.0, 3.0), method='lm')
+
+    def test_m_less_n_not_supported(self):
+        x0 = [-2, 1]
+        assert_raises(ValueError, least_squares, fun_rosenbrock_cropped, x0,
+                      method='lm')
+
+    def test_sparse_not_supported(self):
+        p = BroydenTridiagonal()
+        assert_raises(ValueError, least_squares, p.fun, p.x0, p.jac,
+                      method='lm')
+
+    def test_jac_sparsity_not_supported(self):
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0,
+                      jac_sparsity=[1], method='lm')
+
+    def test_LinearOperator_not_supported(self):
+        p = BroydenTridiagonal(mode="operator")
+        assert_raises(ValueError, least_squares, p.fun, p.x0, p.jac,
+                      method='lm')
+
+    def test_loss(self):
+        res = least_squares(fun_trivial, 2.0, loss='linear', method='lm')
+        assert_allclose(res.x, 0.0, atol=1e-4)
+
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0,
+                      method='lm', loss='huber')
+    
+    def test_callback_with_lm_method(self):
+        def callback(x):
+            assert(False)  # Dummy callback function
+        
+        with suppress_warnings() as sup:
+            sup.filter(
+                UserWarning,
+                "Callback function specified, but not supported with `lm` method."
+            )
+            least_squares(fun_trivial, x0=[0], method='lm', callback=callback)
+
+
+def test_basic():
+    # test that 'method' arg is really optional
+    res = least_squares(fun_trivial, 2.0)
+    assert_allclose(res.x, 0, atol=1e-10)
+
+
+def test_callback():
+    # test that callback function works as expected
+
+    results = []
+    
+    def my_callback_optimresult(intermediate_result: OptimizeResult):
+        results.append(intermediate_result)
+        
+    def my_callback_x(x):
+        r = OptimizeResult()
+        r.nit = 1
+        r.x = x
+        results.append(r)
+        return False
+        
+    def my_callback_optimresult_stop_exception(
+        intermediate_result: OptimizeResult):
+        results.append(intermediate_result)
+        raise StopIteration
+
+    def my_callback_x_stop_exception(x):
+        r = OptimizeResult()
+        r.nit = 1
+        r.x = x
+        results.append(r)
+        raise StopIteration
+
+    # Try for different function signatures and stop methods
+    callbacks_nostop = [my_callback_optimresult, my_callback_x]
+    callbacks_stop = [my_callback_optimresult_stop_exception,
+                      my_callback_x_stop_exception]
+    
+    # Try for all the implemented methods: trf, trf_bounds and dogbox
+    calls = [
+        lambda callback: least_squares(fun_trivial, 5.0, method='trf', 
+                                       callback=callback),
+        lambda callback: least_squares(fun_trivial, 5.0, method='trf', 
+                                       bounds=(-8.0, 8.0), callback=callback),
+        lambda callback: least_squares(fun_trivial, 5.0, method='dogbox', 
+                                       callback=callback)
+    ]
+
+    for mycallback, call in product(callbacks_nostop, calls):
+        results.clear()
+        # Call the different implemented methods
+        res = call(mycallback)
+        # Check that callback was called
+        assert len(results) > 0
+        # Check that results data makes sense
+        assert results[-1].nit > 0
+        # Check that it didn't stop because of the callback
+        assert res.status != -2
+        # final callback x should be same as final result
+        assert_allclose(results[-1].x, res.x)
+
+    for mycallback, call in product(callbacks_stop, calls):
+        results.clear()
+        # Call the different implemented methods
+        res = call(mycallback)
+        # Check that callback was called
+        assert len(results) > 0
+        # Check that only one iteration was run
+        assert results[-1].nit == 1
+        # Check that it stopped because of the callback
+        assert res.status == -2
+
+
+def test_small_tolerances_for_lm():
+    for ftol, xtol, gtol in [(None, 1e-13, 1e-13),
+                             (1e-13, None, 1e-13),
+                             (1e-13, 1e-13, None)]:
+        assert_raises(ValueError, least_squares, fun_trivial, 2.0, xtol=xtol,
+                      ftol=ftol, gtol=gtol, method='lm')
+
+
+def test_fp32_gh12991():
+    # checks that smaller FP sizes can be used in least_squares
+    # this is the minimum working example reported for gh12991
+    rng = np.random.RandomState(1)
+
+    x = np.linspace(0, 1, 100).astype("float32")
+    y = rng.random(100).astype("float32")
+
+    def func(p, x):
+        return p[0] + p[1] * x
+
+    def err(p, x, y):
+        return func(p, x) - y
+
+    res = least_squares(err, [-1.0, -1.0], args=(x, y))
+    # previously the initial jacobian calculated for this would be all 0
+    # and the minimize would terminate immediately, with nfev=1, would
+    # report a successful minimization (it shouldn't have done), but be
+    # unchanged from the initial solution.
+    # It was terminating early because the underlying approx_derivative
+    # used a step size for FP64 when the working space was FP32.
+    assert res.nfev > 2
+    assert_allclose(res.x, np.array([0.4082241, 0.15530563]), atol=5e-5)
+
+
+def test_gh_18793_and_19351():
+    answer = 1e-12
+    initial_guess = 1.1e-12
+
+    def chi2(x):
+        return (x-answer)**2
+
+    gtol = 1e-15
+    res = least_squares(chi2, x0=initial_guess, gtol=1e-15, bounds=(0, np.inf))
+    # Original motivation: gh-18793
+    # if we choose an initial condition that is close to the solution
+    # we shouldn't return an answer that is further away from the solution
+
+    # Update: gh-19351
+    # However this requirement does not go well with 'trf' algorithm logic.
+    # Some regressions were reported after the presumed fix.
+    # The returned solution is good as long as it satisfies the convergence
+    # conditions.
+    # Specifically in this case the scaled gradient will be sufficiently low.
+
+    scaling, _ = CL_scaling_vector(res.x, res.grad,
+                                   np.atleast_1d(0), np.atleast_1d(np.inf))
+    assert res.status == 1  # Converged by gradient
+    assert np.linalg.norm(res.grad * scaling, ord=np.inf) < gtol
+
+
+def test_gh_19103():
+    # Checks that least_squares trf method selects a strictly feasible point,
+    # and thus succeeds instead of failing,
+    # when the initial guess is reported exactly at a boundary point.
+    # This is a reduced example from gh191303
+
+    ydata = np.array([0.] * 66 + [
+        1., 0., 0., 0., 0., 0., 1., 1., 0., 0., 1.,
+        1., 1., 1., 0., 0., 0., 1., 0., 0., 2., 1.,
+        0., 3., 1., 6., 5., 0., 0., 2., 8., 4., 4.,
+        6., 9., 7., 2., 7., 8., 2., 13., 9., 8., 11.,
+        10., 13., 14., 19., 11., 15., 18., 26., 19., 32., 29.,
+        28., 36., 32., 35., 36., 43., 52., 32., 58., 56., 52.,
+        67., 53., 72., 88., 77., 95., 94., 84., 86., 101., 107.,
+        108., 118., 96., 115., 138., 137.,
+    ])
+    xdata = np.arange(0, ydata.size) * 0.1
+
+    def exponential_wrapped(params):
+        A, B, x0 = params
+        return A * np.exp(B * (xdata - x0)) - ydata
+
+    x0 = [0.01, 1., 5.]
+    bounds = ((0.01, 0, 0), (np.inf, 10, 20.9))
+    res = least_squares(exponential_wrapped, x0, method='trf', bounds=bounds)
+    assert res.success

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_linear_assignment.py

@@ -0,0 +1,116 @@
+# Author: Brian M. Clapper, G. Varoquaux, Lars Buitinck
+# License: BSD
+
+from numpy.testing import assert_array_equal
+import pytest
+
+import numpy as np
+
+from scipy.optimize import linear_sum_assignment
+from scipy.sparse import random_array
+from scipy.sparse._sputils import matrix
+from scipy.sparse.csgraph import min_weight_full_bipartite_matching
+from scipy.sparse.csgraph.tests.test_matching import (
+    linear_sum_assignment_assertions, linear_sum_assignment_test_cases
+)
+
+
+def test_linear_sum_assignment_input_shape():
+    with pytest.raises(ValueError, match="expected a matrix"):
+        linear_sum_assignment([1, 2, 3])
+
+
+def test_linear_sum_assignment_input_object():
+    C = [[1, 2, 3], [4, 5, 6]]
+    assert_array_equal(linear_sum_assignment(C),
+                       linear_sum_assignment(np.asarray(C)))
+    assert_array_equal(linear_sum_assignment(C),
+                       linear_sum_assignment(matrix(C)))
+
+
+def test_linear_sum_assignment_input_bool():
+    I = np.identity(3)
+    assert_array_equal(linear_sum_assignment(I.astype(np.bool_)),
+                       linear_sum_assignment(I))
+
+
+def test_linear_sum_assignment_input_string():
+    I = np.identity(3)
+    with pytest.raises(TypeError, match="Cannot cast array data"):
+        linear_sum_assignment(I.astype(str))
+
+
+def test_linear_sum_assignment_input_nan():
+    I = np.diag([np.nan, 1, 1])
+    with pytest.raises(ValueError, match="contains invalid numeric entries"):
+        linear_sum_assignment(I)
+
+
+def test_linear_sum_assignment_input_neginf():
+    I = np.diag([1, -np.inf, 1])
+    with pytest.raises(ValueError, match="contains invalid numeric entries"):
+        linear_sum_assignment(I)
+
+
+def test_linear_sum_assignment_input_inf():
+    I = np.identity(3)
+    I[:, 0] = np.inf
+    with pytest.raises(ValueError, match="cost matrix is infeasible"):
+        linear_sum_assignment(I)
+
+
+def test_constant_cost_matrix():
+    # Fixes #11602
+    n = 8
+    C = np.ones((n, n))
+    row_ind, col_ind = linear_sum_assignment(C)
+    assert_array_equal(row_ind, np.arange(n))
+    assert_array_equal(col_ind, np.arange(n))
+
+
+@pytest.mark.parametrize('num_rows,num_cols', [(0, 0), (2, 0), (0, 3)])
+def test_linear_sum_assignment_trivial_cost(num_rows, num_cols):
+    C = np.empty(shape=(num_cols, num_rows))
+    row_ind, col_ind = linear_sum_assignment(C)
+    assert len(row_ind) == 0
+    assert len(col_ind) == 0
+
+
+@pytest.mark.parametrize('sign,test_case', linear_sum_assignment_test_cases)
+def test_linear_sum_assignment_small_inputs(sign, test_case):
+    linear_sum_assignment_assertions(
+        linear_sum_assignment, np.array, sign, test_case)
+
+
+# Tests that combine scipy.optimize.linear_sum_assignment and
+# scipy.sparse.csgraph.min_weight_full_bipartite_matching
+def test_two_methods_give_same_result_on_many_sparse_inputs():
+    # As opposed to the test above, here we do not spell out the expected
+    # output; only assert that the two methods give the same result.
+    # Concretely, the below tests 100 cases of size 100x100, out of which
+    # 36 are infeasible.
+    np.random.seed(1234)
+    for _ in range(100):
+        lsa_raises = False
+        mwfbm_raises = False
+        sparse = random_array((100, 100), density=0.06,
+                              data_sampler=lambda size: np.random.randint(1, 100, size))
+        # In csgraph, zeros correspond to missing edges, so we explicitly
+        # replace those with infinities
+        dense = np.full(sparse.shape, np.inf)
+        dense[sparse.row, sparse.col] = sparse.data
+        sparse = sparse.tocsr()
+        try:
+            row_ind, col_ind = linear_sum_assignment(dense)
+            lsa_cost = dense[row_ind, col_ind].sum()
+        except ValueError:
+            lsa_raises = True
+        try:
+            row_ind, col_ind = min_weight_full_bipartite_matching(sparse)
+            mwfbm_cost = sparse[row_ind, col_ind].sum()
+        except ValueError:
+            mwfbm_raises = True
+        # Ensure that if one method raises, so does the other one.
+        assert lsa_raises == mwfbm_raises
+        if not lsa_raises:
+            assert lsa_cost == mwfbm_cost

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_linesearch.py

@@ -0,0 +1,328 @@
+"""
+Tests for line search routines
+"""
+from numpy.testing import (assert_equal, assert_array_almost_equal,
+                           assert_array_almost_equal_nulp, assert_warns,
+                           suppress_warnings)
+import scipy.optimize._linesearch as ls
+from scipy.optimize._linesearch import LineSearchWarning
+import numpy as np
+import pytest
+import threading
+
+
+def assert_wolfe(s, phi, derphi, c1=1e-4, c2=0.9, err_msg=""):
+    """
+    Check that strong Wolfe conditions apply
+    """
+    phi1 = phi(s)
+    phi0 = phi(0)
+    derphi0 = derphi(0)
+    derphi1 = derphi(s)
+    msg = (f"s = {s}; phi(0) = {phi0}; phi(s) = {phi1}; phi'(0) = {derphi0};"
+           f" phi'(s) = {derphi1}; {err_msg}")
+
+    assert phi1 <= phi0 + c1*s*derphi0, "Wolfe 1 failed: " + msg
+    assert abs(derphi1) <= abs(c2*derphi0), "Wolfe 2 failed: " + msg
+
+
+def assert_armijo(s, phi, c1=1e-4, err_msg=""):
+    """
+    Check that Armijo condition applies
+    """
+    phi1 = phi(s)
+    phi0 = phi(0)
+    msg = f"s = {s}; phi(0) = {phi0}; phi(s) = {phi1}; {err_msg}"
+    assert phi1 <= (1 - c1*s)*phi0, msg
+
+
+def assert_line_wolfe(x, p, s, f, fprime, **kw):
+    assert_wolfe(s, phi=lambda sp: f(x + p*sp),
+                 derphi=lambda sp: np.dot(fprime(x + p*sp), p), **kw)
+
+
+def assert_line_armijo(x, p, s, f, **kw):
+    assert_armijo(s, phi=lambda sp: f(x + p*sp), **kw)
+
+
+def assert_fp_equal(x, y, err_msg="", nulp=50):
+    """Assert two arrays are equal, up to some floating-point rounding error"""
+    try:
+        assert_array_almost_equal_nulp(x, y, nulp)
+    except AssertionError as e:
+        raise AssertionError(f"{e}\n{err_msg}") from e
+
+
+class TestLineSearch:
+    # -- scalar functions; must have dphi(0.) < 0
+    def _scalar_func_1(self, s):  # skip name check
+        if not hasattr(self.fcount, 'c'):
+            self.fcount.c = 0
+        self.fcount.c += 1
+        p = -s - s**3 + s**4
+        dp = -1 - 3*s**2 + 4*s**3
+        return p, dp
+
+    def _scalar_func_2(self, s):  # skip name check
+        if not hasattr(self.fcount, 'c'):
+            self.fcount.c = 0
+        self.fcount.c += 1
+        p = np.exp(-4*s) + s**2
+        dp = -4*np.exp(-4*s) + 2*s
+        return p, dp
+
+    def _scalar_func_3(self, s):  # skip name check
+        if not hasattr(self.fcount, 'c'):
+            self.fcount.c = 0
+        self.fcount.c += 1
+        p = -np.sin(10*s)
+        dp = -10*np.cos(10*s)
+        return p, dp
+
+    # -- n-d functions
+
+    def _line_func_1(self, x):  # skip name check
+        if not hasattr(self.fcount, 'c'):
+            self.fcount.c = 0
+        self.fcount.c += 1
+        f = np.dot(x, x)
+        df = 2*x
+        return f, df
+
+    def _line_func_2(self, x):  # skip name check
+        if not hasattr(self.fcount, 'c'):
+            self.fcount.c = 0
+        self.fcount.c += 1
+        f = np.dot(x, np.dot(self.A, x)) + 1
+        df = np.dot(self.A + self.A.T, x)
+        return f, df
+
+    # --
+
+    def setup_method(self):
+        self.scalar_funcs = []
+        self.line_funcs = []
+        self.N = 20
+        self.fcount = threading.local()
+
+        def bind_index(func, idx):
+            # Remember Python's closure semantics!
+            return lambda *a, **kw: func(*a, **kw)[idx]
+
+        for name in sorted(dir(self)):
+            if name.startswith('_scalar_func_'):
+                value = getattr(self, name)
+                self.scalar_funcs.append(
+                    (name, bind_index(value, 0), bind_index(value, 1)))
+            elif name.startswith('_line_func_'):
+                value = getattr(self, name)
+                self.line_funcs.append(
+                    (name, bind_index(value, 0), bind_index(value, 1)))
+
+        np.random.seed(1234)
+        self.A = np.random.randn(self.N, self.N)
+
+    def scalar_iter(self):
+        for name, phi, derphi in self.scalar_funcs:
+            for old_phi0 in np.random.randn(3):
+                yield name, phi, derphi, old_phi0
+
+    def line_iter(self):
+        rng = np.random.RandomState(1234)
+        for name, f, fprime in self.line_funcs:
+            k = 0
+            while k < 9:
+                x = rng.randn(self.N)
+                p = rng.randn(self.N)
+                if np.dot(p, fprime(x)) >= 0:
+                    # always pick a descent direction
+                    continue
+                k += 1
+                old_fv = float(rng.randn())
+                yield name, f, fprime, x, p, old_fv
+
+    # -- Generic scalar searches
+
+    def test_scalar_search_wolfe1(self):
+        c = 0
+        for name, phi, derphi, old_phi0 in self.scalar_iter():
+            c += 1
+            s, phi1, phi0 = ls.scalar_search_wolfe1(phi, derphi, phi(0),
+                                                    old_phi0, derphi(0))
+            assert_fp_equal(phi0, phi(0), name)
+            assert_fp_equal(phi1, phi(s), name)
+            assert_wolfe(s, phi, derphi, err_msg=name)
+
+        assert c > 3  # check that the iterator really works...
+
+    def test_scalar_search_wolfe2(self):
+        for name, phi, derphi, old_phi0 in self.scalar_iter():
+            s, phi1, phi0, derphi1 = ls.scalar_search_wolfe2(
+                phi, derphi, phi(0), old_phi0, derphi(0))
+            assert_fp_equal(phi0, phi(0), name)
+            assert_fp_equal(phi1, phi(s), name)
+            if derphi1 is not None:
+                assert_fp_equal(derphi1, derphi(s), name)
+            assert_wolfe(s, phi, derphi, err_msg=f"{name} {old_phi0:g}")
+
+    def test_scalar_search_wolfe2_with_low_amax(self):
+        def phi(alpha):
+            return (alpha - 5) ** 2
+
+        def derphi(alpha):
+            return 2 * (alpha - 5)
+
+        alpha_star, _, _, derphi_star = ls.scalar_search_wolfe2(phi, derphi, amax=0.001)
+        assert alpha_star is None  # Not converged
+        assert derphi_star is None  # Not converged
+
+    def test_scalar_search_wolfe2_regression(self):
+        # Regression test for gh-12157
+        # This phi has its minimum at alpha=4/3 ~ 1.333.
+        def phi(alpha):
+            if alpha < 1:
+                return - 3*np.pi/2 * (alpha - 1)
+            else:
+                return np.cos(3*np.pi/2 * alpha - np.pi)
+
+        def derphi(alpha):
+            if alpha < 1:
+                return - 3*np.pi/2
+            else:
+                return - 3*np.pi/2 * np.sin(3*np.pi/2 * alpha - np.pi)
+
+        s, _, _, _ = ls.scalar_search_wolfe2(phi, derphi)
+        # Without the fix in gh-13073, the scalar_search_wolfe2
+        # returned s=2.0 instead.
+        assert s < 1.5
+
+    def test_scalar_search_armijo(self):
+        for name, phi, derphi, old_phi0 in self.scalar_iter():
+            s, phi1 = ls.scalar_search_armijo(phi, phi(0), derphi(0))
+            assert_fp_equal(phi1, phi(s), name)
+            assert_armijo(s, phi, err_msg=f"{name} {old_phi0:g}")
+
+    # -- Generic line searches
+
+    def test_line_search_wolfe1(self):
+        c = 0
+        smax = 100
+        for name, f, fprime, x, p, old_f in self.line_iter():
+            f0 = f(x)
+            g0 = fprime(x)
+            self.fcount.c = 0
+            s, fc, gc, fv, ofv, gv = ls.line_search_wolfe1(f, fprime, x, p,
+                                                           g0, f0, old_f,
+                                                           amax=smax)
+            assert_equal(self.fcount.c, fc+gc)
+            assert_fp_equal(ofv, f(x))
+            if s is None:
+                continue
+            assert_fp_equal(fv, f(x + s*p))
+            assert_array_almost_equal(gv, fprime(x + s*p), decimal=14)
+            if s < smax:
+                c += 1
+                assert_line_wolfe(x, p, s, f, fprime, err_msg=name)
+
+        assert c > 3  # check that the iterator really works...
+
+    def test_line_search_wolfe2(self):
+        c = 0
+        smax = 512
+        for name, f, fprime, x, p, old_f in self.line_iter():
+            f0 = f(x)
+            g0 = fprime(x)
+            self.fcount.c = 0
+            with suppress_warnings() as sup:
+                sup.filter(LineSearchWarning,
+                           "The line search algorithm could not find a solution")
+                sup.filter(LineSearchWarning,
+                           "The line search algorithm did not converge")
+                s, fc, gc, fv, ofv, gv = ls.line_search_wolfe2(f, fprime, x, p,
+                                                               g0, f0, old_f,
+                                                               amax=smax)
+            assert_equal(self.fcount.c, fc+gc)
+            assert_fp_equal(ofv, f(x))
+            assert_fp_equal(fv, f(x + s*p))
+            if gv is not None:
+                assert_array_almost_equal(gv, fprime(x + s*p), decimal=14)
+            if s < smax:
+                c += 1
+                assert_line_wolfe(x, p, s, f, fprime, err_msg=name)
+        assert c > 3  # check that the iterator really works...
+
+    @pytest.mark.thread_unsafe
+    def test_line_search_wolfe2_bounds(self):
+        # See gh-7475
+
+        # For this f and p, starting at a point on axis 0, the strong Wolfe
+        # condition 2 is met if and only if the step length s satisfies
+        # |x + s| <= c2 * |x|
+        def f(x):
+            return np.dot(x, x)
+        def fp(x):
+            return 2 * x
+        p = np.array([1, 0])
+
+        # Smallest s satisfying strong Wolfe conditions for these arguments is 30
+        x = -60 * p
+        c2 = 0.5
+
+        s, _, _, _, _, _ = ls.line_search_wolfe2(f, fp, x, p, amax=30, c2=c2)
+        assert_line_wolfe(x, p, s, f, fp)
+
+        s, _, _, _, _, _ = assert_warns(LineSearchWarning,
+                                        ls.line_search_wolfe2, f, fp, x, p,
+                                        amax=29, c2=c2)
+        assert s is None
+
+        # s=30 will only be tried on the 6th iteration, so this won't converge
+        assert_warns(LineSearchWarning, ls.line_search_wolfe2, f, fp, x, p,
+                     c2=c2, maxiter=5)
+
+    def test_line_search_armijo(self):
+        c = 0
+        for name, f, fprime, x, p, old_f in self.line_iter():
+            f0 = f(x)
+            g0 = fprime(x)
+            self.fcount.c = 0
+            s, fc, fv = ls.line_search_armijo(f, x, p, g0, f0)
+            c += 1
+            assert_equal(self.fcount.c, fc)
+            assert_fp_equal(fv, f(x + s*p))
+            assert_line_armijo(x, p, s, f, err_msg=name)
+        assert c >= 9
+
+    # -- More specific tests
+
+    def test_armijo_terminate_1(self):
+        # Armijo should evaluate the function only once if the trial step
+        # is already suitable
+        count = [0]
+
+        def phi(s):
+            count[0] += 1
+            return -s + 0.01*s**2
+        s, phi1 = ls.scalar_search_armijo(phi, phi(0), -1, alpha0=1)
+        assert_equal(s, 1)
+        assert_equal(count[0], 2)
+        assert_armijo(s, phi)
+
+    def test_wolfe_terminate(self):
+        # wolfe1 and wolfe2 should also evaluate the function only a few
+        # times if the trial step is already suitable
+
+        def phi(s):
+            count[0] += 1
+            return -s + 0.05*s**2
+
+        def derphi(s):
+            count[0] += 1
+            return -1 + 0.05*2*s
+
+        for func in [ls.scalar_search_wolfe1, ls.scalar_search_wolfe2]:
+            count = [0]
+            r = func(phi, derphi, phi(0), None, derphi(0))
+            assert r[0] is not None, (r, func)
+            assert count[0] <= 2 + 2, (count, func)
+            assert_wolfe(r[0], phi, derphi, err_msg=str(func))

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_lsq_common.py

@@ -0,0 +1,297 @@
+from numpy.testing import assert_, assert_allclose, assert_equal
+from pytest import raises as assert_raises
+import numpy as np
+
+from scipy.optimize._lsq.common import (
+    step_size_to_bound, find_active_constraints, make_strictly_feasible,
+    CL_scaling_vector, intersect_trust_region, build_quadratic_1d,
+    minimize_quadratic_1d, evaluate_quadratic, reflective_transformation,
+    left_multiplied_operator, right_multiplied_operator)
+
+
+class TestBounds:
+    def test_step_size_to_bounds(self):
+        lb = np.array([-1.0, 2.5, 10.0])
+        ub = np.array([1.0, 5.0, 100.0])
+        x = np.array([0.0, 2.5, 12.0])
+
+        s = np.array([0.1, 0.0, 0.0])
+        step, hits = step_size_to_bound(x, s, lb, ub)
+        assert_equal(step, 10)
+        assert_equal(hits, [1, 0, 0])
+
+        s = np.array([0.01, 0.05, -1.0])
+        step, hits = step_size_to_bound(x, s, lb, ub)
+        assert_equal(step, 2)
+        assert_equal(hits, [0, 0, -1])
+
+        s = np.array([10.0, -0.0001, 100.0])
+        step, hits = step_size_to_bound(x, s, lb, ub)
+        assert_equal(step, np.array(-0))
+        assert_equal(hits, [0, -1, 0])
+
+        s = np.array([1.0, 0.5, -2.0])
+        step, hits = step_size_to_bound(x, s, lb, ub)
+        assert_equal(step, 1.0)
+        assert_equal(hits, [1, 0, -1])
+
+        s = np.zeros(3)
+        step, hits = step_size_to_bound(x, s, lb, ub)
+        assert_equal(step, np.inf)
+        assert_equal(hits, [0, 0, 0])
+
+    def test_find_active_constraints(self):
+        lb = np.array([0.0, -10.0, 1.0])
+        ub = np.array([1.0, 0.0, 100.0])
+
+        x = np.array([0.5, -5.0, 2.0])
+        active = find_active_constraints(x, lb, ub)
+        assert_equal(active, [0, 0, 0])
+
+        x = np.array([0.0, 0.0, 10.0])
+        active = find_active_constraints(x, lb, ub)
+        assert_equal(active, [-1, 1, 0])
+
+        active = find_active_constraints(x, lb, ub, rtol=0)
+        assert_equal(active, [-1, 1, 0])
+
+        x = np.array([1e-9, -1e-8, 100 - 1e-9])
+        active = find_active_constraints(x, lb, ub)
+        assert_equal(active, [0, 0, 1])
+
+        active = find_active_constraints(x, lb, ub, rtol=1.5e-9)
+        assert_equal(active, [-1, 0, 1])
+
+        lb = np.array([1.0, -np.inf, -np.inf])
+        ub = np.array([np.inf, 10.0, np.inf])
+
+        x = np.ones(3)
+        active = find_active_constraints(x, lb, ub)
+        assert_equal(active, [-1, 0, 0])
+
+        # Handles out-of-bound cases.
+        x = np.array([0.0, 11.0, 0.0])
+        active = find_active_constraints(x, lb, ub)
+        assert_equal(active, [-1, 1, 0])
+
+        active = find_active_constraints(x, lb, ub, rtol=0)
+        assert_equal(active, [-1, 1, 0])
+
+    def test_make_strictly_feasible(self):
+        lb = np.array([-0.5, -0.8, 2.0])
+        ub = np.array([0.8, 1.0, 3.0])
+
+        x = np.array([-0.5, 0.0, 2 + 1e-10])
+
+        x_new = make_strictly_feasible(x, lb, ub, rstep=0)
+        assert_(x_new[0] > -0.5)
+        assert_equal(x_new[1:], x[1:])
+
+        x_new = make_strictly_feasible(x, lb, ub, rstep=1e-4)
+        assert_equal(x_new, [-0.5 + 1e-4, 0.0, 2 * (1 + 1e-4)])
+
+        x = np.array([-0.5, -1, 3.1])
+        x_new = make_strictly_feasible(x, lb, ub)
+        assert_(np.all((x_new >= lb) & (x_new <= ub)))
+
+        x_new = make_strictly_feasible(x, lb, ub, rstep=0)
+        assert_(np.all((x_new >= lb) & (x_new <= ub)))
+
+        lb = np.array([-1, 100.0])
+        ub = np.array([1, 100.0 + 1e-10])
+        x = np.array([0, 100.0])
+        x_new = make_strictly_feasible(x, lb, ub, rstep=1e-8)
+        assert_equal(x_new, [0, 100.0 + 0.5e-10])
+
+    def test_scaling_vector(self):
+        lb = np.array([-np.inf, -5.0, 1.0, -np.inf])
+        ub = np.array([1.0, np.inf, 10.0, np.inf])
+        x = np.array([0.5, 2.0, 5.0, 0.0])
+        g = np.array([1.0, 0.1, -10.0, 0.0])
+        v, dv = CL_scaling_vector(x, g, lb, ub)
+        assert_equal(v, [1.0, 7.0, 5.0, 1.0])
+        assert_equal(dv, [0.0, 1.0, -1.0, 0.0])
+
+
+class TestQuadraticFunction:
+    def setup_method(self):
+        self.J = np.array([
+            [0.1, 0.2],
+            [-1.0, 1.0],
+            [0.5, 0.2]])
+        self.g = np.array([0.8, -2.0])
+        self.diag = np.array([1.0, 2.0])
+
+    def test_build_quadratic_1d(self):
+        s = np.zeros(2)
+        a, b = build_quadratic_1d(self.J, self.g, s)
+        assert_equal(a, 0)
+        assert_equal(b, 0)
+
+        a, b = build_quadratic_1d(self.J, self.g, s, diag=self.diag)
+        assert_equal(a, 0)
+        assert_equal(b, 0)
+
+        s = np.array([1.0, -1.0])
+        a, b = build_quadratic_1d(self.J, self.g, s)
+        assert_equal(a, 2.05)
+        assert_equal(b, 2.8)
+
+        a, b = build_quadratic_1d(self.J, self.g, s, diag=self.diag)
+        assert_equal(a, 3.55)
+        assert_equal(b, 2.8)
+
+        s0 = np.array([0.5, 0.5])
+        a, b, c = build_quadratic_1d(self.J, self.g, s, diag=self.diag, s0=s0)
+        assert_equal(a, 3.55)
+        assert_allclose(b, 2.39)
+        assert_allclose(c, -0.1525)
+
+    def test_minimize_quadratic_1d(self):
+        a = 5
+        b = -1
+
+        t, y = minimize_quadratic_1d(a, b, 1, 2)
+        assert_equal(t, 1)
+        assert_allclose(y, a * t**2 + b * t, rtol=1e-15)
+
+        t, y = minimize_quadratic_1d(a, b, -2, -1)
+        assert_equal(t, -1)
+        assert_allclose(y, a * t**2 + b * t, rtol=1e-15)
+
+        t, y = minimize_quadratic_1d(a, b, -1, 1)
+        assert_equal(t, 0.1)
+        assert_allclose(y, a * t**2 + b * t, rtol=1e-15)
+
+        c = 10
+        t, y = minimize_quadratic_1d(a, b, -1, 1, c=c)
+        assert_equal(t, 0.1)
+        assert_allclose(y, a * t**2 + b * t + c, rtol=1e-15)
+
+        t, y = minimize_quadratic_1d(a, b, -np.inf, np.inf, c=c)
+        assert_equal(t, 0.1)
+        assert_allclose(y, a * t ** 2 + b * t + c, rtol=1e-15)
+
+        t, y = minimize_quadratic_1d(a, b, 0, np.inf, c=c)
+        assert_equal(t, 0.1)
+        assert_allclose(y, a * t ** 2 + b * t + c, rtol=1e-15)
+
+        t, y = minimize_quadratic_1d(a, b, -np.inf, 0, c=c)
+        assert_equal(t, 0)
+        assert_allclose(y, a * t ** 2 + b * t + c, rtol=1e-15)
+
+        a = -1
+        b = 0.2
+        t, y = minimize_quadratic_1d(a, b, -np.inf, np.inf)
+        assert_equal(y, -np.inf)
+
+        t, y = minimize_quadratic_1d(a, b, 0, np.inf)
+        assert_equal(t, np.inf)
+        assert_equal(y, -np.inf)
+
+        t, y = minimize_quadratic_1d(a, b, -np.inf, 0)
+        assert_equal(t, -np.inf)
+        assert_equal(y, -np.inf)
+
+    def test_evaluate_quadratic(self):
+        s = np.array([1.0, -1.0])
+
+        value = evaluate_quadratic(self.J, self.g, s)
+        assert_equal(value, 4.85)
+
+        value = evaluate_quadratic(self.J, self.g, s, diag=self.diag)
+        assert_equal(value, 6.35)
+
+        s = np.array([[1.0, -1.0],
+                     [1.0, 1.0],
+                     [0.0, 0.0]])
+
+        values = evaluate_quadratic(self.J, self.g, s)
+        assert_allclose(values, [4.85, -0.91, 0.0])
+
+        values = evaluate_quadratic(self.J, self.g, s, diag=self.diag)
+        assert_allclose(values, [6.35, 0.59, 0.0])
+
+
+class TestTrustRegion:
+    def test_intersect(self):
+        Delta = 1.0
+
+        x = np.zeros(3)
+        s = np.array([1.0, 0.0, 0.0])
+        t_neg, t_pos = intersect_trust_region(x, s, Delta)
+        assert_equal(t_neg, -1)
+        assert_equal(t_pos, 1)
+
+        s = np.array([-1.0, 1.0, -1.0])
+        t_neg, t_pos = intersect_trust_region(x, s, Delta)
+        assert_allclose(t_neg, -3**-0.5)
+        assert_allclose(t_pos, 3**-0.5)
+
+        x = np.array([0.5, -0.5, 0])
+        s = np.array([0, 0, 1.0])
+        t_neg, t_pos = intersect_trust_region(x, s, Delta)
+        assert_allclose(t_neg, -2**-0.5)
+        assert_allclose(t_pos, 2**-0.5)
+
+        x = np.ones(3)
+        assert_raises(ValueError, intersect_trust_region, x, s, Delta)
+
+        x = np.zeros(3)
+        s = np.zeros(3)
+        assert_raises(ValueError, intersect_trust_region, x, s, Delta)
+
+
+def test_reflective_transformation():
+    lb = np.array([-1, -2], dtype=float)
+    ub = np.array([5, 3], dtype=float)
+
+    y = np.array([0, 0])
+    x, g = reflective_transformation(y, lb, ub)
+    assert_equal(x, y)
+    assert_equal(g, np.ones(2))
+
+    y = np.array([-4, 4], dtype=float)
+
+    x, g = reflective_transformation(y, lb, np.array([np.inf, np.inf]))
+    assert_equal(x, [2, 4])
+    assert_equal(g, [-1, 1])
+
+    x, g = reflective_transformation(y, np.array([-np.inf, -np.inf]), ub)
+    assert_equal(x, [-4, 2])
+    assert_equal(g, [1, -1])
+
+    x, g = reflective_transformation(y, lb, ub)
+    assert_equal(x, [2, 2])
+    assert_equal(g, [-1, -1])
+
+    lb = np.array([-np.inf, -2])
+    ub = np.array([5, np.inf])
+    y = np.array([10, 10], dtype=float)
+    x, g = reflective_transformation(y, lb, ub)
+    assert_equal(x, [0, 10])
+    assert_equal(g, [-1, 1])
+
+
+def test_linear_operators():
+    A = np.arange(6).reshape((3, 2))
+
+    d_left = np.array([-1, 2, 5])
+    DA = np.diag(d_left).dot(A)
+    J_left = left_multiplied_operator(A, d_left)
+
+    d_right = np.array([5, 10])
+    AD = A.dot(np.diag(d_right))
+    J_right = right_multiplied_operator(A, d_right)
+
+    x = np.array([-2, 3])
+    X = -2 * np.arange(2, 8).reshape((2, 3))
+    xt = np.array([0, -2, 15])
+
+    assert_allclose(DA.dot(x), J_left.matvec(x))
+    assert_allclose(DA.dot(X), J_left.matmat(X))
+    assert_allclose(DA.T.dot(xt), J_left.rmatvec(xt))
+
+    assert_allclose(AD.dot(x), J_right.matvec(x))
+    assert_allclose(AD.dot(X), J_right.matmat(X))
+    assert_allclose(AD.T.dot(xt), J_right.rmatvec(xt))

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_lsq_linear.py

@@ -0,0 +1,287 @@
+import pytest
+
+import numpy as np
+from numpy.linalg import lstsq
+from numpy.testing import assert_allclose, assert_equal, assert_
+
+from scipy.sparse import random_array, coo_array
+from scipy.sparse.linalg import aslinearoperator
+from scipy.optimize import lsq_linear
+from scipy.optimize._minimize import Bounds
+
+
+A = np.array([
+    [0.171, -0.057],
+    [-0.049, -0.248],
+    [-0.166, 0.054],
+])
+b = np.array([0.074, 1.014, -0.383])
+
+
+class BaseMixin:
+    def setup_method(self):
+        self.rnd = np.random.RandomState(0)
+
+    def test_dense_no_bounds(self):
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, method=self.method, lsq_solver=lsq_solver)
+            assert_allclose(res.x, lstsq(A, b, rcond=-1)[0])
+            assert_allclose(res.x, res.unbounded_sol[0])
+
+    def test_dense_bounds(self):
+        # Solutions for comparison are taken from MATLAB.
+        lb = np.array([-1, -10])
+        ub = np.array([1, 0])
+        unbounded_sol = lstsq(A, b, rcond=-1)[0]
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, (lb, ub), method=self.method,
+                             lsq_solver=lsq_solver)
+            assert_allclose(res.x, lstsq(A, b, rcond=-1)[0])
+            assert_allclose(res.unbounded_sol[0], unbounded_sol)
+
+        lb = np.array([0.0, -np.inf])
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, (lb, np.inf), method=self.method,
+                             lsq_solver=lsq_solver)
+            assert_allclose(res.x, np.array([0.0, -4.084174437334673]),
+                            atol=1e-6)
+            assert_allclose(res.unbounded_sol[0], unbounded_sol)
+
+        lb = np.array([-1, 0])
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, (lb, np.inf), method=self.method,
+                             lsq_solver=lsq_solver)
+            assert_allclose(res.x, np.array([0.448427311733504, 0]),
+                            atol=1e-15)
+            assert_allclose(res.unbounded_sol[0], unbounded_sol)
+
+        ub = np.array([np.inf, -5])
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, (-np.inf, ub), method=self.method,
+                             lsq_solver=lsq_solver)
+            assert_allclose(res.x, np.array([-0.105560998682388, -5]))
+            assert_allclose(res.unbounded_sol[0], unbounded_sol)
+
+        ub = np.array([-1, np.inf])
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, (-np.inf, ub), method=self.method,
+                             lsq_solver=lsq_solver)
+            assert_allclose(res.x, np.array([-1, -4.181102129483254]))
+            assert_allclose(res.unbounded_sol[0], unbounded_sol)
+
+        lb = np.array([0, -4])
+        ub = np.array([1, 0])
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, (lb, ub), method=self.method,
+                             lsq_solver=lsq_solver)
+            assert_allclose(res.x, np.array([0.005236663400791, -4]))
+            assert_allclose(res.unbounded_sol[0], unbounded_sol)
+
+    def test_bounds_variants(self):
+        x = np.array([1, 3])
+        A = self.rnd.uniform(size=(2, 2))
+        b = A@x
+        lb = np.array([1, 1])
+        ub = np.array([2, 2])
+        bounds_old = (lb, ub)
+        bounds_new = Bounds(lb, ub)
+        res_old = lsq_linear(A, b, bounds_old)
+        res_new = lsq_linear(A, b, bounds_new)
+        assert not np.allclose(res_new.x, res_new.unbounded_sol[0])
+        assert_allclose(res_old.x, res_new.x)
+
+    def test_np_matrix(self):
+        # gh-10711
+        with np.testing.suppress_warnings() as sup:
+            sup.filter(PendingDeprecationWarning)
+            A = np.matrix([[20, -4, 0, 2, 3], [10, -2, 1, 0, -1]])
+        k = np.array([20, 15])
+        lsq_linear(A, k)
+
+    def test_dense_rank_deficient(self):
+        A = np.array([[-0.307, -0.184]])
+        b = np.array([0.773])
+        lb = [-0.1, -0.1]
+        ub = [0.1, 0.1]
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, (lb, ub), method=self.method,
+                             lsq_solver=lsq_solver)
+            assert_allclose(res.x, [-0.1, -0.1])
+            assert_allclose(res.unbounded_sol[0], lstsq(A, b, rcond=-1)[0])
+
+        A = np.array([
+            [0.334, 0.668],
+            [-0.516, -1.032],
+            [0.192, 0.384],
+        ])
+        b = np.array([-1.436, 0.135, 0.909])
+        lb = [0, -1]
+        ub = [1, -0.5]
+        for lsq_solver in self.lsq_solvers:
+            res = lsq_linear(A, b, (lb, ub), method=self.method,
+                             lsq_solver=lsq_solver)
+            assert_allclose(res.optimality, 0, atol=1e-11)
+            assert_allclose(res.unbounded_sol[0], lstsq(A, b, rcond=-1)[0])
+
+    def test_full_result(self):
+        lb = np.array([0, -4])
+        ub = np.array([1, 0])
+        res = lsq_linear(A, b, (lb, ub), method=self.method)
+
+        assert_allclose(res.x, [0.005236663400791, -4])
+        assert_allclose(res.unbounded_sol[0], lstsq(A, b, rcond=-1)[0])
+
+        r = A.dot(res.x) - b
+        assert_allclose(res.cost, 0.5 * np.dot(r, r))
+        assert_allclose(res.fun, r)
+
+        assert_allclose(res.optimality, 0.0, atol=1e-12)
+        assert_equal(res.active_mask, [0, -1])
+        assert_(res.nit < 15)
+        assert_(res.status == 1 or res.status == 3)
+        assert_(isinstance(res.message, str))
+        assert_(res.success)
+
+    # This is a test for issue #9982.
+    def test_almost_singular(self):
+        A = np.array(
+            [[0.8854232310355122, 0.0365312146937765, 0.0365312146836789],
+             [0.3742460132129041, 0.0130523214078376, 0.0130523214077873],
+             [0.9680633871281361, 0.0319366128718639, 0.0319366128718388]])
+
+        b = np.array(
+            [0.0055029366538097, 0.0026677442422208, 0.0066612514782381])
+
+        result = lsq_linear(A, b, method=self.method)
+        assert_(result.cost < 1.1e-8)
+
+    @pytest.mark.xslow
+    def test_large_rank_deficient(self):
+        np.random.seed(0)
+        n, m = np.sort(np.random.randint(2, 1000, size=2))
+        m *= 2   # make m >> n
+        A = 1.0 * np.random.randint(-99, 99, size=[m, n])
+        b = 1.0 * np.random.randint(-99, 99, size=[m])
+        bounds = 1.0 * np.sort(np.random.randint(-99, 99, size=(2, n)), axis=0)
+        bounds[1, :] += 1.0  # ensure up > lb
+
+        # Make the A matrix strongly rank deficient by replicating some columns
+        w = np.random.choice(n, n)  # Select random columns with duplicates
+        A = A[:, w]
+
+        x_bvls = lsq_linear(A, b, bounds=bounds, method='bvls').x
+        x_trf = lsq_linear(A, b, bounds=bounds, method='trf').x
+
+        cost_bvls = np.sum((A @ x_bvls - b)**2)
+        cost_trf = np.sum((A @ x_trf - b)**2)
+
+        assert_(abs(cost_bvls - cost_trf) < cost_trf*1e-10)
+
+    def test_convergence_small_array(self):
+        A = np.array([[49.0, 41.0, -32.0],
+                      [-19.0, -32.0, -8.0],
+                      [-13.0, 10.0, 69.0]])
+        b = np.array([-41.0, -90.0, 47.0])
+        bounds = np.array([[31.0, -44.0, 26.0],
+                           [54.0, -32.0, 28.0]])
+
+        x_bvls = lsq_linear(A, b, bounds=bounds, method='bvls').x
+        x_trf = lsq_linear(A, b, bounds=bounds, method='trf').x
+
+        cost_bvls = np.sum((A @ x_bvls - b)**2)
+        cost_trf = np.sum((A @ x_trf - b)**2)
+
+        assert_(abs(cost_bvls - cost_trf) < cost_trf*1e-10)
+
+
+class SparseMixin:
+    def test_sparse_and_LinearOperator(self):
+        m = 5000
+        n = 1000
+        rng = np.random.RandomState(0)
+        A = random_array((m, n), random_state=rng)
+        b = rng.randn(m)
+        res = lsq_linear(A, b)
+        assert_allclose(res.optimality, 0, atol=1e-6)
+
+        A = aslinearoperator(A)
+        res = lsq_linear(A, b)
+        assert_allclose(res.optimality, 0, atol=1e-6)
+
+    @pytest.mark.fail_slow(10)
+    def test_sparse_bounds(self):
+        m = 5000
+        n = 1000
+        rng = np.random.RandomState(0)
+        A = random_array((m, n), random_state=rng)
+        b = rng.randn(m)
+        lb = rng.randn(n)
+        ub = lb + 1
+        res = lsq_linear(A, b, (lb, ub))
+        assert_allclose(res.optimality, 0.0, atol=1e-6)
+
+        res = lsq_linear(A, b, (lb, ub), lsmr_tol=1e-13,
+                         lsmr_maxiter=1500)
+        assert_allclose(res.optimality, 0.0, atol=1e-6)
+
+        res = lsq_linear(A, b, (lb, ub), lsmr_tol='auto')
+        assert_allclose(res.optimality, 0.0, atol=1e-6)
+
+    def test_sparse_ill_conditioned(self):
+        # Sparse matrix with condition number of ~4 million
+        data = np.array([1., 1., 1., 1. + 1e-6, 1.])
+        row = np.array([0, 0, 1, 2, 2])
+        col = np.array([0, 2, 1, 0, 2])
+        A = coo_array((data, (row, col)), shape=(3, 3))
+
+        # Get the exact solution
+        exact_sol = lsq_linear(A.toarray(), b, lsq_solver='exact')
+
+        # Default lsmr arguments should not fully converge the solution
+        default_lsmr_sol = lsq_linear(A, b, lsq_solver='lsmr')
+        with pytest.raises(AssertionError):
+            assert_allclose(exact_sol.x, default_lsmr_sol.x)
+
+        # By increasing the maximum lsmr iters, it will converge
+        conv_lsmr = lsq_linear(A, b, lsq_solver='lsmr', lsmr_maxiter=10)
+        assert_allclose(exact_sol.x, conv_lsmr.x)
+
+
+class TestTRF(BaseMixin, SparseMixin):
+    method = 'trf'
+    lsq_solvers = ['exact', 'lsmr']
+
+
+class TestBVLS(BaseMixin):
+    method = 'bvls'
+    lsq_solvers = ['exact']
+
+
+class TestErrorChecking:
+    def test_option_lsmr_tol(self):
+        # Should work with a positive float, string equal to 'auto', or None
+        _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_tol=1e-2)
+        _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_tol='auto')
+        _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_tol=None)
+
+        # Should raise error with negative float, strings
+        # other than 'auto', and integers
+        err_message = "`lsmr_tol` must be None, 'auto', or positive float."
+        with pytest.raises(ValueError, match=err_message):
+            _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_tol=-0.1)
+        with pytest.raises(ValueError, match=err_message):
+            _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_tol='foo')
+        with pytest.raises(ValueError, match=err_message):
+            _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_tol=1)
+
+    def test_option_lsmr_maxiter(self):
+        # Should work with positive integers or None
+        _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_maxiter=1)
+        _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_maxiter=None)
+
+        # Should raise error with 0 or negative max iter
+        err_message = "`lsmr_maxiter` must be None or positive integer."
+        with pytest.raises(ValueError, match=err_message):
+            _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_maxiter=0)
+        with pytest.raises(ValueError, match=err_message):
+            _ = lsq_linear(A, b, lsq_solver='lsmr', lsmr_maxiter=-1)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_milp.py

@@ -0,0 +1,459 @@
+"""
+Unit test for Mixed Integer Linear Programming
+"""
+import re
+import sys
+
+import numpy as np
+from numpy.testing import assert_allclose, assert_array_equal
+import pytest
+
+from .test_linprog import magic_square
+from scipy.optimize import milp, Bounds, LinearConstraint
+from scipy import sparse
+
+
+_IS_32BIT = (sys.maxsize < 2**32)
+
+def test_milp_iv():
+
+    message = "`c` must be a dense array"
+    with pytest.raises(ValueError, match=message):
+        milp(sparse.coo_array([0, 0]))
+
+    message = "`c` must be a one-dimensional array of finite numbers with"
+    with pytest.raises(ValueError, match=message):
+        milp(np.zeros((3, 4)))
+    with pytest.raises(ValueError, match=message):
+        milp([])
+    with pytest.raises(ValueError, match=message):
+        milp(None)
+
+    message = "`bounds` must be convertible into an instance of..."
+    with pytest.raises(ValueError, match=message):
+        milp(1, bounds=10)
+
+    message = "`constraints` (or each element within `constraints`) must be"
+    with pytest.raises(ValueError, match=re.escape(message)):
+        milp(1, constraints=10)
+    with pytest.raises(ValueError, match=re.escape(message)):
+        milp(np.zeros(3), constraints=([[1, 2, 3]], [2, 3], [2, 3]))
+    with pytest.raises(ValueError, match=re.escape(message)):
+        milp(np.zeros(2), constraints=([[1, 2]], [2], sparse.coo_array([2])))
+
+    message = "The shape of `A` must be (len(b_l), len(c))."
+    with pytest.raises(ValueError, match=re.escape(message)):
+        milp(np.zeros(3), constraints=([[1, 2]], [2], [2]))
+
+    message = "`integrality` must be a dense array"
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2], integrality=sparse.coo_array([1, 2]))
+
+    message = ("`integrality` must contain integers 0-3 and be broadcastable "
+               "to `c.shape`.")
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2, 3], integrality=[1, 2])
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2, 3], integrality=[1, 5, 3])
+
+    message = "Lower and upper bounds must be dense arrays."
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2, 3], bounds=([1, 2], sparse.coo_array([3, 4])))
+
+    message = "`lb`, `ub`, and `keep_feasible` must be broadcastable."
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2, 3], bounds=([1, 2], [3, 4, 5]))
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2, 3], bounds=([1, 2, 3], [4, 5]))
+
+    message = "`bounds.lb` and `bounds.ub` must contain reals and..."
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2, 3], bounds=([1, 2], [3, 4]))
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2, 3], bounds=([1, 2, 3], ["3+4", 4, 5]))
+    with pytest.raises(ValueError, match=message):
+        milp([1, 2, 3], bounds=([1, 2, 3], [set(), 4, 5]))
+
+
+@pytest.mark.xfail(run=False,
+                   reason="Needs to be fixed in `_highs_wrapper`")
+def test_milp_options(capsys):
+    # run=False now because of gh-16347
+    message = "Unrecognized options detected: {'ekki'}..."
+    options = {'ekki': True}
+    with pytest.warns(RuntimeWarning, match=message):
+        milp(1, options=options)
+
+    A, b, c, numbers, M = magic_square(3)
+    options = {"disp": True, "presolve": False, "time_limit": 0.05}
+    res = milp(c=c, constraints=(A, b, b), bounds=(0, 1), integrality=1,
+               options=options)
+
+    captured = capsys.readouterr()
+    assert "Presolve is switched off" in captured.out
+    assert "Time Limit Reached" in captured.out
+    assert not res.success
+
+
+def test_result():
+    A, b, c, numbers, M = magic_square(3)
+    res = milp(c=c, constraints=(A, b, b), bounds=(0, 1), integrality=1)
+    assert res.status == 0
+    assert res.success
+    msg = "Optimization terminated successfully. (HiGHS Status 7:"
+    assert res.message.startswith(msg)
+    assert isinstance(res.x, np.ndarray)
+    assert isinstance(res.fun, float)
+    assert isinstance(res.mip_node_count, int)
+    assert isinstance(res.mip_dual_bound, float)
+    assert isinstance(res.mip_gap, float)
+
+    A, b, c, numbers, M = magic_square(6)
+    res = milp(c=c*0, constraints=(A, b, b), bounds=(0, 1), integrality=1,
+               options={'time_limit': 0.05})
+    assert res.status == 1
+    assert not res.success
+    msg = "Time limit reached. (HiGHS Status 13:"
+    assert res.message.startswith(msg)
+    assert (res.fun is res.mip_dual_bound is res.mip_gap
+            is res.mip_node_count is res.x is None)
+
+    res = milp(1, bounds=(1, -1))
+    assert res.status == 2
+    assert not res.success
+    msg = "The problem is infeasible. (HiGHS Status 8:"
+    assert res.message.startswith(msg)
+    assert (res.fun is res.mip_dual_bound is res.mip_gap
+            is res.mip_node_count is res.x is None)
+
+    res = milp(-1)
+    assert res.status == 3
+    assert not res.success
+    msg = "The problem is unbounded. (HiGHS Status 10:"
+    assert res.message.startswith(msg)
+    assert (res.fun is res.mip_dual_bound is res.mip_gap
+            is res.mip_node_count is res.x is None)
+
+
+def test_milp_optional_args():
+    # check that arguments other than `c` are indeed optional
+    res = milp(1)
+    assert res.fun == 0
+    assert_array_equal(res.x, [0])
+
+
+def test_milp_1():
+    # solve magic square problem
+    n = 3
+    A, b, c, numbers, M = magic_square(n)
+    A = sparse.csc_array(A)  # confirm that sparse arrays are accepted
+    res = milp(c=c*0, constraints=(A, b, b), bounds=(0, 1), integrality=1)
+
+    # check that solution is a magic square
+    x = np.round(res.x)
+    s = (numbers.flatten() * x).reshape(n**2, n, n)
+    square = np.sum(s, axis=0)
+    np.testing.assert_allclose(square.sum(axis=0), M)
+    np.testing.assert_allclose(square.sum(axis=1), M)
+    np.testing.assert_allclose(np.diag(square).sum(), M)
+    np.testing.assert_allclose(np.diag(square[:, ::-1]).sum(), M)
+
+
+def test_milp_2():
+    # solve MIP with inequality constraints and all integer constraints
+    # source: slide 5,
+    # https://www.cs.upc.edu/~erodri/webpage/cps/theory/lp/milp/slides.pdf
+    # also check that `milp` accepts all valid ways of specifying constraints
+    c = -np.ones(2)
+    A = [[-2, 2], [-8, 10]]
+    b_l = [1, -np.inf]
+    b_u = [np.inf, 13]
+    linear_constraint = LinearConstraint(A, b_l, b_u)
+
+    # solve original problem
+    res1 = milp(c=c, constraints=(A, b_l, b_u), integrality=True)
+    res2 = milp(c=c, constraints=linear_constraint, integrality=True)
+    res3 = milp(c=c, constraints=[(A, b_l, b_u)], integrality=True)
+    res4 = milp(c=c, constraints=[linear_constraint], integrality=True)
+    res5 = milp(c=c, integrality=True,
+                constraints=[(A[:1], b_l[:1], b_u[:1]),
+                             (A[1:], b_l[1:], b_u[1:])])
+    res6 = milp(c=c, integrality=True,
+                constraints=[LinearConstraint(A[:1], b_l[:1], b_u[:1]),
+                             LinearConstraint(A[1:], b_l[1:], b_u[1:])])
+    res7 = milp(c=c, integrality=True,
+                constraints=[(A[:1], b_l[:1], b_u[:1]),
+                             LinearConstraint(A[1:], b_l[1:], b_u[1:])])
+    xs = np.array([res1.x, res2.x, res3.x, res4.x, res5.x, res6.x, res7.x])
+    funs = np.array([res1.fun, res2.fun, res3.fun,
+                     res4.fun, res5.fun, res6.fun, res7.fun])
+    np.testing.assert_allclose(xs, np.broadcast_to([1, 2], xs.shape))
+    np.testing.assert_allclose(funs, -3)
+
+    # solve relaxed problem
+    res = milp(c=c, constraints=(A, b_l, b_u))
+    np.testing.assert_allclose(res.x, [4, 4.5])
+    np.testing.assert_allclose(res.fun, -8.5)
+
+
+def test_milp_3():
+    # solve MIP with inequality constraints and all integer constraints
+    # source: https://en.wikipedia.org/wiki/Integer_programming#Example
+    c = [0, -1]
+    A = [[-1, 1], [3, 2], [2, 3]]
+    b_u = [1, 12, 12]
+    b_l = np.full_like(b_u, -np.inf, dtype=np.float64)
+    constraints = LinearConstraint(A, b_l, b_u)
+
+    integrality = np.ones_like(c)
+
+    # solve original problem
+    res = milp(c=c, constraints=constraints, integrality=integrality)
+    assert_allclose(res.fun, -2)
+    # two optimal solutions possible, just need one of them
+    assert np.allclose(res.x, [1, 2]) or np.allclose(res.x, [2, 2])
+
+    # solve relaxed problem
+    res = milp(c=c, constraints=constraints)
+    assert_allclose(res.fun, -2.8)
+    assert_allclose(res.x, [1.8, 2.8])
+
+
+def test_milp_4():
+    # solve MIP with inequality constraints and only one integer constraint
+    # source: https://www.mathworks.com/help/optim/ug/intlinprog.html
+    c = [8, 1]
+    integrality = [0, 1]
+    A = [[1, 2], [-4, -1], [2, 1]]
+    b_l = [-14, -np.inf, -np.inf]
+    b_u = [np.inf, -33, 20]
+    constraints = LinearConstraint(A, b_l, b_u)
+    bounds = Bounds(-np.inf, np.inf)
+
+    res = milp(c, integrality=integrality, bounds=bounds,
+               constraints=constraints)
+    assert_allclose(res.fun, 59)
+    assert_allclose(res.x, [6.5, 7])
+
+
+def test_milp_5():
+    # solve MIP with inequality and equality constraints
+    # source: https://www.mathworks.com/help/optim/ug/intlinprog.html
+    c = [-3, -2, -1]
+    integrality = [0, 0, 1]
+    lb = [0, 0, 0]
+    ub = [np.inf, np.inf, 1]
+    bounds = Bounds(lb, ub)
+    A = [[1, 1, 1], [4, 2, 1]]
+    b_l = [-np.inf, 12]
+    b_u = [7, 12]
+    constraints = LinearConstraint(A, b_l, b_u)
+
+    res = milp(c, integrality=integrality, bounds=bounds,
+               constraints=constraints)
+    # there are multiple solutions
+    assert_allclose(res.fun, -12)
+
+
+@pytest.mark.xslow
+def test_milp_6():
+    # solve a larger MIP with only equality constraints
+    # source: https://www.mathworks.com/help/optim/ug/intlinprog.html
+    integrality = 1
+    A_eq = np.array([[22, 13, 26, 33, 21, 3, 14, 26],
+                     [39, 16, 22, 28, 26, 30, 23, 24],
+                     [18, 14, 29, 27, 30, 38, 26, 26],
+                     [41, 26, 28, 36, 18, 38, 16, 26]])
+    b_eq = np.array([7872, 10466, 11322, 12058])
+    c = np.array([2, 10, 13, 17, 7, 5, 7, 3])
+
+    res = milp(c=c, constraints=(A_eq, b_eq, b_eq), integrality=integrality)
+
+    np.testing.assert_allclose(res.fun, 1854)
+
+
+def test_infeasible_prob_16609():
+    # Ensure presolve does not mark trivially infeasible problems
+    # as Optimal -- see gh-16609
+    c = [1.0, 0.0]
+    integrality = [0, 1]
+
+    lb = [0, -np.inf]
+    ub = [np.inf, np.inf]
+    bounds = Bounds(lb, ub)
+
+    A_eq = [[0.0, 1.0]]
+    b_eq = [0.5]
+    constraints = LinearConstraint(A_eq, b_eq, b_eq)
+
+    res = milp(c, integrality=integrality, bounds=bounds,
+               constraints=constraints)
+    np.testing.assert_equal(res.status, 2)
+
+
+_msg_time = "Time limit reached. (HiGHS Status 13:"
+_msg_iter = "Iteration limit reached. (HiGHS Status 14:"
+
+@pytest.mark.thread_unsafe
+# See https://github.com/scipy/scipy/pull/19255#issuecomment-1778438888
+@pytest.mark.xfail(reason="Often buggy, revisit with callbacks, gh-19255")
+@pytest.mark.skipif(np.intp(0).itemsize < 8,
+                    reason="Unhandled 32-bit GCC FP bug")
+@pytest.mark.slow
+@pytest.mark.parametrize(["options", "msg"], [({"time_limit": 0.1}, _msg_time),
+                                              ({"node_limit": 1}, _msg_iter)])
+def test_milp_timeout_16545(options, msg):
+    # Ensure solution is not thrown away if MILP solver times out
+    # -- see gh-16545
+    rng = np.random.default_rng(5123833489170494244)
+    A = rng.integers(0, 5, size=(100, 100))
+    b_lb = np.full(100, fill_value=-np.inf)
+    b_ub = np.full(100, fill_value=25)
+    constraints = LinearConstraint(A, b_lb, b_ub)
+    variable_lb = np.zeros(100)
+    variable_ub = np.ones(100)
+    variable_bounds = Bounds(variable_lb, variable_ub)
+    integrality = np.ones(100)
+    c_vector = -np.ones(100)
+    res = milp(
+        c_vector,
+        integrality=integrality,
+        bounds=variable_bounds,
+        constraints=constraints,
+        options=options,
+    )
+
+    assert res.message.startswith(msg)
+    assert res["x"] is not None
+
+    # ensure solution is feasible
+    x = res["x"]
+    tol = 1e-8  # sometimes needed due to finite numerical precision
+    assert np.all(b_lb - tol <= A @ x) and np.all(A @ x <= b_ub + tol)
+    assert np.all(variable_lb - tol <= x) and np.all(x <= variable_ub + tol)
+    assert np.allclose(x, np.round(x))
+
+
+def test_three_constraints_16878():
+    # `milp` failed when exactly three constraints were passed
+    # Ensure that this is no longer the case.
+    rng = np.random.default_rng(5123833489170494244)
+    A = rng.integers(0, 5, size=(6, 6))
+    bl = np.full(6, fill_value=-np.inf)
+    bu = np.full(6, fill_value=10)
+    constraints = [LinearConstraint(A[:2], bl[:2], bu[:2]),
+                   LinearConstraint(A[2:4], bl[2:4], bu[2:4]),
+                   LinearConstraint(A[4:], bl[4:], bu[4:])]
+    constraints2 = [(A[:2], bl[:2], bu[:2]),
+                    (A[2:4], bl[2:4], bu[2:4]),
+                    (A[4:], bl[4:], bu[4:])]
+    lb = np.zeros(6)
+    ub = np.ones(6)
+    variable_bounds = Bounds(lb, ub)
+    c = -np.ones(6)
+    res1 = milp(c, bounds=variable_bounds, constraints=constraints)
+    res2 = milp(c, bounds=variable_bounds, constraints=constraints2)
+    ref = milp(c, bounds=variable_bounds, constraints=(A, bl, bu))
+    assert res1.success and res2.success
+    assert_allclose(res1.x, ref.x)
+    assert_allclose(res2.x, ref.x)
+
+
+@pytest.mark.xslow
+def test_mip_rel_gap_passdown():
+    # Solve problem with decreasing mip_gap to make sure mip_rel_gap decreases
+    # Adapted from test_linprog::TestLinprogHiGHSMIP::test_mip_rel_gap_passdown
+    # MIP taken from test_mip_6 above
+    A_eq = np.array([[22, 13, 26, 33, 21, 3, 14, 26],
+                     [39, 16, 22, 28, 26, 30, 23, 24],
+                     [18, 14, 29, 27, 30, 38, 26, 26],
+                     [41, 26, 28, 36, 18, 38, 16, 26]])
+    b_eq = np.array([7872, 10466, 11322, 12058])
+    c = np.array([2, 10, 13, 17, 7, 5, 7, 3])
+
+    mip_rel_gaps = [0.25, 0.01, 0.001]
+    sol_mip_gaps = []
+    for mip_rel_gap in mip_rel_gaps:
+        res = milp(c=c, bounds=(0, np.inf), constraints=(A_eq, b_eq, b_eq),
+                   integrality=True, options={"mip_rel_gap": mip_rel_gap})
+        # assert that the solution actually has mip_gap lower than the
+        # required mip_rel_gap supplied
+        assert res.mip_gap <= mip_rel_gap
+        # check that `res.mip_gap` is as defined in the documentation
+        assert res.mip_gap == (res.fun - res.mip_dual_bound)/res.fun
+        sol_mip_gaps.append(res.mip_gap)
+
+    # make sure that the mip_rel_gap parameter is actually doing something
+    # check that differences between solution gaps are declining
+    # monotonically with the mip_rel_gap parameter.
+    assert np.all(np.diff(sol_mip_gaps) < 0)
+
+@pytest.mark.xfail(reason='Upstream / Wrapper issue, see gh-20116')
+def test_large_numbers_gh20116():
+    h = 10 ** 12
+    A = np.array([[100.4534, h], [100.4534, -h]])
+    b = np.array([h, 0])
+    constraints = LinearConstraint(A=A, ub=b)
+    bounds = Bounds([0, 0], [1, 1])
+    c = np.array([0, 0])
+    res = milp(c=c, constraints=constraints, bounds=bounds, integrality=1)
+    assert res.status == 0
+    assert np.all(A @ res.x < b)
+
+
+def test_presolve_gh18907():
+    from scipy.optimize import milp
+    import numpy as np
+    inf = np.inf
+
+    # set up problem
+    c = np.array([-0.85850509, -0.82892676, -0.80026454, -0.63015535, -0.5099006,
+                  -0.50077193, -0.4894404, -0.47285865,  -0.39867774, -0.38069646,
+                  -0.36733012, -0.36733012, -0.35820411, -0.31576141, -0.20626091,
+                  -0.12466144, -0.10679516, -0.1061887, -0.1061887, -0.1061887,
+                  -0., -0., -0., -0., 0., 0., 0., 0.])
+
+    A = np.array([[1., 1., 1., 1., 1., 1., 1., 1., 1., 1., 1., 1., 1., 1.,
+                   1., 1., 1., 1., 1., 1., 1., 1., 1., 1., 0., 0., 0., 0.],
+                  [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
+                   1., 0., 0., 0., 0., 0., 1., 0., 0., 0., -25., -0., -0., -0.],
+                  [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
+                   -1., 0., 0., 0., 0., 0., -1., 0., 0., 0., 2., 0., 0., 0.],
+                  [0., 0., 0., 0., 1., 1., 1., 1., 0., 1., 0., 0., 0., 0., 0.,
+                   0., 0., 0., 0., 0., 0., 0., 0., 0., -0., -25., -0., -0.],
+                  [0., 0., 0., 0., -1., -1., -1., -1., 0., -1., 0., 0., 0.,
+                   0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 2., 0., 0.],
+                  [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
+                   0., 0., 1., 1., 1., 0., 0., 0., 0., -0., -0., -25., -0.],
+                  [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
+                   0., 0., -1., -1., -1., 0., 0., 0., 0., 0., 0., 2., 0.],
+                  [1., 1., 1., 1., 0., 0., 0., 0., 1., 0., 1., 1., 1., 1., 0.,
+                   1., 1., 0., 0., 0., 0., 1., 1., 1., -0., -0., -0., -25.],
+                  [-1., -1., -1., -1., 0., 0., 0., 0., -1., 0., -1., -1., -1., -1.,
+                   0., -1., -1., 0., 0., 0., 0., -1., -1., -1., 0., 0., 0., 2.]])
+    bl = np.array([-inf, -inf, -inf, -inf, -inf, -inf, -inf, -inf, -inf])
+    bu = np.array([100., 0., 0., 0., 0., 0., 0., 0., 0.])
+    constraints = LinearConstraint(A, bl, bu)
+    integrality = 1
+    bounds = (0, 1)
+    r1 = milp(c=c, constraints=constraints, integrality=integrality, bounds=bounds,
+              options={'presolve': True})
+    r2 = milp(c=c, constraints=constraints, integrality=integrality, bounds=bounds,
+              options={'presolve': False})
+    assert r1.status == r2.status
+    assert_allclose(r1.x, r2.x)
+
+    # another example from the same issue
+    bounds = Bounds(lb=0, ub=1)
+    integrality = [1, 1, 0, 0]
+    c = [10, 9.52380952, -1000, -952.38095238]
+    A = [[1, 1, 0, 0], [0, 0, 1, 1], [200, 0, 0, 0], [0, 200, 0, 0],
+         [0, 0, 2000, 0], [0, 0, 0, 2000], [-1, 0, 1, 0], [-1, -1, 0, 1]]
+    ub = [1, 1, 200, 200, 1000, 1000, 0, 0]
+    constraints = LinearConstraint(A, ub=ub)
+    r1 = milp(c=c, constraints=constraints,  bounds=bounds,
+              integrality=integrality, options={"presolve": False})
+    r2 = milp(c=c, constraints=constraints,  bounds=bounds,
+              integrality=integrality, options={"presolve": False})
+    assert r1.status == r2.status
+    assert_allclose(r1.x, r2.x)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_minimize_constrained.py

@@ -0,0 +1,845 @@
+import numpy as np
+import pytest
+from scipy.linalg import block_diag
+from scipy.sparse import csc_array
+from numpy.testing import (assert_array_almost_equal,
+                           assert_array_less, assert_,
+                           suppress_warnings)
+from scipy.optimize import (NonlinearConstraint,
+                            LinearConstraint,
+                            Bounds,
+                            minimize,
+                            BFGS,
+                            SR1,
+                            rosen)
+
+
+class Maratos:
+    """Problem 15.4 from Nocedal and Wright
+
+    The following optimization problem:
+        minimize 2*(x[0]**2 + x[1]**2 - 1) - x[0]
+        Subject to: x[0]**2 + x[1]**2 - 1 = 0
+    """
+
+    def __init__(self, degrees=60, constr_jac=None, constr_hess=None):
+        rads = degrees/180*np.pi
+        self.x0 = [np.cos(rads), np.sin(rads)]
+        self.x_opt = np.array([1.0, 0.0])
+        self.constr_jac = constr_jac
+        self.constr_hess = constr_hess
+        self.bounds = None
+
+    def fun(self, x):
+        return 2*(x[0]**2 + x[1]**2 - 1) - x[0]
+
+    def grad(self, x):
+        return np.array([4*x[0]-1, 4*x[1]])
+
+    def hess(self, x):
+        return 4*np.eye(2)
+
+    @property
+    def constr(self):
+        def fun(x):
+            return x[0]**2 + x[1]**2
+
+        if self.constr_jac is None:
+            def jac(x):
+                return [[2*x[0], 2*x[1]]]
+        else:
+            jac = self.constr_jac
+
+        if self.constr_hess is None:
+            def hess(x, v):
+                return 2*v[0]*np.eye(2)
+        else:
+            hess = self.constr_hess
+
+        return NonlinearConstraint(fun, 1, 1, jac, hess)
+
+
+class MaratosTestArgs:
+    """Problem 15.4 from Nocedal and Wright
+
+    The following optimization problem:
+        minimize 2*(x[0]**2 + x[1]**2 - 1) - x[0]
+        Subject to: x[0]**2 + x[1]**2 - 1 = 0
+    """
+
+    def __init__(self, a, b, degrees=60, constr_jac=None, constr_hess=None):
+        rads = degrees/180*np.pi
+        self.x0 = [np.cos(rads), np.sin(rads)]
+        self.x_opt = np.array([1.0, 0.0])
+        self.constr_jac = constr_jac
+        self.constr_hess = constr_hess
+        self.a = a
+        self.b = b
+        self.bounds = None
+
+    def _test_args(self, a, b):
+        if self.a != a or self.b != b:
+            raise ValueError()
+
+    def fun(self, x, a, b):
+        self._test_args(a, b)
+        return 2*(x[0]**2 + x[1]**2 - 1) - x[0]
+
+    def grad(self, x, a, b):
+        self._test_args(a, b)
+        return np.array([4*x[0]-1, 4*x[1]])
+
+    def hess(self, x, a, b):
+        self._test_args(a, b)
+        return 4*np.eye(2)
+
+    @property
+    def constr(self):
+        def fun(x):
+            return x[0]**2 + x[1]**2
+
+        if self.constr_jac is None:
+            def jac(x):
+                return [[4*x[0], 4*x[1]]]
+        else:
+            jac = self.constr_jac
+
+        if self.constr_hess is None:
+            def hess(x, v):
+                return 2*v[0]*np.eye(2)
+        else:
+            hess = self.constr_hess
+
+        return NonlinearConstraint(fun, 1, 1, jac, hess)
+
+
+class MaratosGradInFunc:
+    """Problem 15.4 from Nocedal and Wright
+
+    The following optimization problem:
+        minimize 2*(x[0]**2 + x[1]**2 - 1) - x[0]
+        Subject to: x[0]**2 + x[1]**2 - 1 = 0
+    """
+
+    def __init__(self, degrees=60, constr_jac=None, constr_hess=None):
+        rads = degrees/180*np.pi
+        self.x0 = [np.cos(rads), np.sin(rads)]
+        self.x_opt = np.array([1.0, 0.0])
+        self.constr_jac = constr_jac
+        self.constr_hess = constr_hess
+        self.bounds = None
+
+    def fun(self, x):
+        return (2*(x[0]**2 + x[1]**2 - 1) - x[0],
+                np.array([4*x[0]-1, 4*x[1]]))
+
+    @property
+    def grad(self):
+        return True
+
+    def hess(self, x):
+        return 4*np.eye(2)
+
+    @property
+    def constr(self):
+        def fun(x):
+            return x[0]**2 + x[1]**2
+
+        if self.constr_jac is None:
+            def jac(x):
+                return [[4*x[0], 4*x[1]]]
+        else:
+            jac = self.constr_jac
+
+        if self.constr_hess is None:
+            def hess(x, v):
+                return 2*v[0]*np.eye(2)
+        else:
+            hess = self.constr_hess
+
+        return NonlinearConstraint(fun, 1, 1, jac, hess)
+
+
+class HyperbolicIneq:
+    """Problem 15.1 from Nocedal and Wright
+
+    The following optimization problem:
+        minimize 1/2*(x[0] - 2)**2 + 1/2*(x[1] - 1/2)**2
+        Subject to: 1/(x[0] + 1) - x[1] >= 1/4
+                                   x[0] >= 0
+                                   x[1] >= 0
+    """
+    def __init__(self, constr_jac=None, constr_hess=None):
+        self.x0 = [0, 0]
+        self.x_opt = [1.952823, 0.088659]
+        self.constr_jac = constr_jac
+        self.constr_hess = constr_hess
+        self.bounds = Bounds(0, np.inf)
+
+    def fun(self, x):
+        return 1/2*(x[0] - 2)**2 + 1/2*(x[1] - 1/2)**2
+
+    def grad(self, x):
+        return [x[0] - 2, x[1] - 1/2]
+
+    def hess(self, x):
+        return np.eye(2)
+
+    @property
+    def constr(self):
+        def fun(x):
+            return 1/(x[0] + 1) - x[1]
+
+        if self.constr_jac is None:
+            def jac(x):
+                return [[-1/(x[0] + 1)**2, -1]]
+        else:
+            jac = self.constr_jac
+
+        if self.constr_hess is None:
+            def hess(x, v):
+                return 2*v[0]*np.array([[1/(x[0] + 1)**3, 0],
+                                        [0, 0]])
+        else:
+            hess = self.constr_hess
+
+        return NonlinearConstraint(fun, 0.25, np.inf, jac, hess)
+
+
+class Rosenbrock:
+    """Rosenbrock function.
+
+    The following optimization problem:
+        minimize sum(100.0*(x[1:] - x[:-1]**2.0)**2.0 + (1 - x[:-1])**2.0)
+    """
+
+    def __init__(self, n=2, random_state=0):
+        rng = np.random.RandomState(random_state)
+        self.x0 = rng.uniform(-1, 1, n)
+        self.x_opt = np.ones(n)
+        self.bounds = None
+
+    def fun(self, x):
+        x = np.asarray(x)
+        r = np.sum(100.0 * (x[1:] - x[:-1]**2.0)**2.0 + (1 - x[:-1])**2.0,
+                   axis=0)
+        return r
+
+    def grad(self, x):
+        x = np.asarray(x)
+        xm = x[1:-1]
+        xm_m1 = x[:-2]
+        xm_p1 = x[2:]
+        der = np.zeros_like(x)
+        der[1:-1] = (200 * (xm - xm_m1**2) -
+                     400 * (xm_p1 - xm**2) * xm - 2 * (1 - xm))
+        der[0] = -400 * x[0] * (x[1] - x[0]**2) - 2 * (1 - x[0])
+        der[-1] = 200 * (x[-1] - x[-2]**2)
+        return der
+
+    def hess(self, x):
+        x = np.atleast_1d(x)
+        H = np.diag(-400 * x[:-1], 1) - np.diag(400 * x[:-1], -1)
+        diagonal = np.zeros(len(x), dtype=x.dtype)
+        diagonal[0] = 1200 * x[0]**2 - 400 * x[1] + 2
+        diagonal[-1] = 200
+        diagonal[1:-1] = 202 + 1200 * x[1:-1]**2 - 400 * x[2:]
+        H = H + np.diag(diagonal)
+        return H
+
+    @property
+    def constr(self):
+        return ()
+
+
+class IneqRosenbrock(Rosenbrock):
+    """Rosenbrock subject to inequality constraints.
+
+    The following optimization problem:
+        minimize sum(100.0*(x[1] - x[0]**2)**2.0 + (1 - x[0])**2)
+        subject to: x[0] + 2 x[1] <= 1
+
+    Taken from matlab ``fmincon`` documentation.
+    """
+    def __init__(self, random_state=0):
+        Rosenbrock.__init__(self, 2, random_state)
+        self.x0 = [-1, -0.5]
+        self.x_opt = [0.5022, 0.2489]
+        self.bounds = None
+
+    @property
+    def constr(self):
+        A = [[1, 2]]
+        b = 1
+        return LinearConstraint(A, -np.inf, b)
+
+
+class BoundedRosenbrock(Rosenbrock):
+    """Rosenbrock subject to inequality constraints.
+
+    The following optimization problem:
+        minimize sum(100.0*(x[1] - x[0]**2)**2.0 + (1 - x[0])**2)
+        subject to:  -2 <= x[0] <= 0
+                      0 <= x[1] <= 2
+
+    Taken from matlab ``fmincon`` documentation.
+    """
+    def __init__(self, random_state=0):
+        Rosenbrock.__init__(self, 2, random_state)
+        self.x0 = [-0.2, 0.2]
+        self.x_opt = None
+        self.bounds = Bounds([-2, 0], [0, 2])
+
+
+class EqIneqRosenbrock(Rosenbrock):
+    """Rosenbrock subject to equality and inequality constraints.
+
+    The following optimization problem:
+        minimize sum(100.0*(x[1] - x[0]**2)**2.0 + (1 - x[0])**2)
+        subject to: x[0] + 2 x[1] <= 1
+                    2 x[0] + x[1] = 1
+
+    Taken from matlab ``fimincon`` documentation.
+    """
+    def __init__(self, random_state=0):
+        Rosenbrock.__init__(self, 2, random_state)
+        self.x0 = [-1, -0.5]
+        self.x_opt = [0.41494, 0.17011]
+        self.bounds = None
+
+    @property
+    def constr(self):
+        A_ineq = [[1, 2]]
+        b_ineq = 1
+        A_eq = [[2, 1]]
+        b_eq = 1
+        return (LinearConstraint(A_ineq, -np.inf, b_ineq),
+                LinearConstraint(A_eq, b_eq, b_eq))
+
+
+class Elec:
+    """Distribution of electrons on a sphere.
+
+    Problem no 2 from COPS collection [2]_. Find
+    the equilibrium state distribution (of minimal
+    potential) of the electrons positioned on a
+    conducting sphere.
+
+    References
+    ----------
+    .. [1] E. D. Dolan, J. J. Mor\'{e}, and T. S. Munson,
+           "Benchmarking optimization software with COPS 3.0.",
+            Argonne National Lab., Argonne, IL (US), 2004.
+    """
+    def __init__(self, n_electrons=200, random_state=0,
+                 constr_jac=None, constr_hess=None):
+        self.n_electrons = n_electrons
+        self.rng = np.random.RandomState(random_state)
+        # Initial Guess
+        phi = self.rng.uniform(0, 2 * np.pi, self.n_electrons)
+        theta = self.rng.uniform(-np.pi, np.pi, self.n_electrons)
+        x = np.cos(theta) * np.cos(phi)
+        y = np.cos(theta) * np.sin(phi)
+        z = np.sin(theta)
+        self.x0 = np.hstack((x, y, z))
+        self.x_opt = None
+        self.constr_jac = constr_jac
+        self.constr_hess = constr_hess
+        self.bounds = None
+
+    def _get_cordinates(self, x):
+        x_coord = x[:self.n_electrons]
+        y_coord = x[self.n_electrons:2 * self.n_electrons]
+        z_coord = x[2 * self.n_electrons:]
+        return x_coord, y_coord, z_coord
+
+    def _compute_coordinate_deltas(self, x):
+        x_coord, y_coord, z_coord = self._get_cordinates(x)
+        dx = x_coord[:, None] - x_coord
+        dy = y_coord[:, None] - y_coord
+        dz = z_coord[:, None] - z_coord
+        return dx, dy, dz
+
+    def fun(self, x):
+        dx, dy, dz = self._compute_coordinate_deltas(x)
+        with np.errstate(divide='ignore'):
+            dm1 = (dx**2 + dy**2 + dz**2) ** -0.5
+        dm1[np.diag_indices_from(dm1)] = 0
+        return 0.5 * np.sum(dm1)
+
+    def grad(self, x):
+        dx, dy, dz = self._compute_coordinate_deltas(x)
+
+        with np.errstate(divide='ignore'):
+            dm3 = (dx**2 + dy**2 + dz**2) ** -1.5
+        dm3[np.diag_indices_from(dm3)] = 0
+
+        grad_x = -np.sum(dx * dm3, axis=1)
+        grad_y = -np.sum(dy * dm3, axis=1)
+        grad_z = -np.sum(dz * dm3, axis=1)
+
+        return np.hstack((grad_x, grad_y, grad_z))
+
+    def hess(self, x):
+        dx, dy, dz = self._compute_coordinate_deltas(x)
+        d = (dx**2 + dy**2 + dz**2) ** 0.5
+
+        with np.errstate(divide='ignore'):
+            dm3 = d ** -3
+            dm5 = d ** -5
+
+        i = np.arange(self.n_electrons)
+        dm3[i, i] = 0
+        dm5[i, i] = 0
+
+        Hxx = dm3 - 3 * dx**2 * dm5
+        Hxx[i, i] = -np.sum(Hxx, axis=1)
+
+        Hxy = -3 * dx * dy * dm5
+        Hxy[i, i] = -np.sum(Hxy, axis=1)
+
+        Hxz = -3 * dx * dz * dm5
+        Hxz[i, i] = -np.sum(Hxz, axis=1)
+
+        Hyy = dm3 - 3 * dy**2 * dm5
+        Hyy[i, i] = -np.sum(Hyy, axis=1)
+
+        Hyz = -3 * dy * dz * dm5
+        Hyz[i, i] = -np.sum(Hyz, axis=1)
+
+        Hzz = dm3 - 3 * dz**2 * dm5
+        Hzz[i, i] = -np.sum(Hzz, axis=1)
+
+        H = np.vstack((
+            np.hstack((Hxx, Hxy, Hxz)),
+            np.hstack((Hxy, Hyy, Hyz)),
+            np.hstack((Hxz, Hyz, Hzz))
+        ))
+
+        return H
+
+    @property
+    def constr(self):
+        def fun(x):
+            x_coord, y_coord, z_coord = self._get_cordinates(x)
+            return x_coord**2 + y_coord**2 + z_coord**2 - 1
+
+        if self.constr_jac is None:
+            def jac(x):
+                x_coord, y_coord, z_coord = self._get_cordinates(x)
+                Jx = 2 * np.diag(x_coord)
+                Jy = 2 * np.diag(y_coord)
+                Jz = 2 * np.diag(z_coord)
+                return csc_array(np.hstack((Jx, Jy, Jz)))
+        else:
+            jac = self.constr_jac
+
+        if self.constr_hess is None:
+            def hess(x, v):
+                D = 2 * np.diag(v)
+                return block_diag(D, D, D)
+        else:
+            hess = self.constr_hess
+
+        return NonlinearConstraint(fun, -np.inf, 0, jac, hess)
+
+
+class TestTrustRegionConstr:
+    list_of_problems = [Maratos(),
+                        Maratos(constr_hess='2-point'),
+                        Maratos(constr_hess=SR1()),
+                        Maratos(constr_jac='2-point', constr_hess=SR1()),
+                        MaratosGradInFunc(),
+                        HyperbolicIneq(),
+                        HyperbolicIneq(constr_hess='3-point'),
+                        HyperbolicIneq(constr_hess=BFGS()),
+                        HyperbolicIneq(constr_jac='3-point',
+                                       constr_hess=BFGS()),
+                        Rosenbrock(),
+                        IneqRosenbrock(),
+                        EqIneqRosenbrock(),
+                        BoundedRosenbrock(),
+                        Elec(n_electrons=2),
+                        Elec(n_electrons=2, constr_hess='2-point'),
+                        Elec(n_electrons=2, constr_hess=SR1()),
+                        Elec(n_electrons=2, constr_jac='3-point',
+                             constr_hess=SR1())]
+
+    @pytest.mark.thread_unsafe
+    @pytest.mark.parametrize('prob', list_of_problems)
+    @pytest.mark.parametrize('grad', ('prob.grad', '3-point', False))
+    @pytest.mark.parametrize('hess', ("prob.hess", '3-point', SR1(),
+                                      BFGS(exception_strategy='damp_update'),
+                                      BFGS(exception_strategy='skip_update')))
+    def test_list_of_problems(self, prob, grad, hess):
+        grad = prob.grad if grad == "prob.grad" else grad
+        hess = prob.hess if hess == "prob.hess" else hess
+        # Remove exceptions
+        if (grad in {'2-point', '3-point', 'cs', False} and
+                hess in {'2-point', '3-point', 'cs'}):
+            pytest.skip("Numerical Hessian needs analytical gradient")
+        if prob.grad is True and grad in {'3-point', False}:
+            pytest.skip("prob.grad incompatible with grad in {'3-point', False}")
+        sensitive = (isinstance(prob, BoundedRosenbrock) and grad == '3-point'
+                     and isinstance(hess, BFGS))
+        if sensitive:
+            pytest.xfail("Seems sensitive to initial conditions w/ Accelerate")
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "delta_grad == 0.0")
+            result = minimize(prob.fun, prob.x0,
+                              method='trust-constr',
+                              jac=grad, hess=hess,
+                              bounds=prob.bounds,
+                              constraints=prob.constr)
+
+        if prob.x_opt is not None:
+            assert_array_almost_equal(result.x, prob.x_opt,
+                                      decimal=5)
+            # gtol
+            if result.status == 1:
+                assert_array_less(result.optimality, 1e-8)
+        # xtol
+        if result.status == 2:
+            assert_array_less(result.tr_radius, 1e-8)
+
+            if result.method == "tr_interior_point":
+                assert_array_less(result.barrier_parameter, 1e-8)
+
+        # check for max iter
+        message = f"Invalid termination condition: {result.status}."
+        assert result.status not in {0, 3}, message
+
+
+    def test_default_jac_and_hess(self):
+        def fun(x):
+            return (x - 1) ** 2
+        bounds = [(-2, 2)]
+        res = minimize(fun, x0=[-1.5], bounds=bounds, method='trust-constr')
+        assert_array_almost_equal(res.x, 1, decimal=5)
+
+    def test_default_hess(self):
+        def fun(x):
+            return (x - 1) ** 2
+        bounds = [(-2, 2)]
+        res = minimize(fun, x0=[-1.5], bounds=bounds, method='trust-constr',
+                       jac='2-point')
+        assert_array_almost_equal(res.x, 1, decimal=5)
+
+    def test_no_constraints(self):
+        prob = Rosenbrock()
+        result = minimize(prob.fun, prob.x0,
+                          method='trust-constr',
+                          jac=prob.grad, hess=prob.hess)
+        result1 = minimize(prob.fun, prob.x0,
+                           method='L-BFGS-B',
+                           jac='2-point')
+
+        result2 = minimize(prob.fun, prob.x0,
+                           method='L-BFGS-B',
+                           jac='3-point')
+        assert_array_almost_equal(result.x, prob.x_opt, decimal=5)
+        assert_array_almost_equal(result1.x, prob.x_opt, decimal=5)
+        assert_array_almost_equal(result2.x, prob.x_opt, decimal=5)
+
+    def test_hessp(self):
+        prob = Maratos()
+
+        def hessp(x, p):
+            H = prob.hess(x)
+            return H.dot(p)
+
+        result = minimize(prob.fun, prob.x0,
+                          method='trust-constr',
+                          jac=prob.grad, hessp=hessp,
+                          bounds=prob.bounds,
+                          constraints=prob.constr)
+
+        if prob.x_opt is not None:
+            assert_array_almost_equal(result.x, prob.x_opt, decimal=2)
+
+        # gtol
+        if result.status == 1:
+            assert_array_less(result.optimality, 1e-8)
+        # xtol
+        if result.status == 2:
+            assert_array_less(result.tr_radius, 1e-8)
+
+            if result.method == "tr_interior_point":
+                assert_array_less(result.barrier_parameter, 1e-8)
+        # max iter
+        if result.status in (0, 3):
+            raise RuntimeError("Invalid termination condition.")
+
+    def test_args(self):
+        prob = MaratosTestArgs("a", 234)
+
+        result = minimize(prob.fun, prob.x0, ("a", 234),
+                          method='trust-constr',
+                          jac=prob.grad, hess=prob.hess,
+                          bounds=prob.bounds,
+                          constraints=prob.constr)
+
+        if prob.x_opt is not None:
+            assert_array_almost_equal(result.x, prob.x_opt, decimal=2)
+
+        # gtol
+        if result.status == 1:
+            assert_array_less(result.optimality, 1e-8)
+        # xtol
+        if result.status == 2:
+            assert_array_less(result.tr_radius, 1e-8)
+            if result.method == "tr_interior_point":
+                assert_array_less(result.barrier_parameter, 1e-8)
+        # max iter
+        if result.status in (0, 3):
+            raise RuntimeError("Invalid termination condition.")
+
+    def test_raise_exception(self):
+        prob = Maratos()
+        message = "Whenever the gradient is estimated via finite-differences"
+        with pytest.raises(ValueError, match=message):
+            minimize(prob.fun, prob.x0, method='trust-constr', jac='2-point',
+                     hess='2-point', constraints=prob.constr)
+
+    def test_issue_9044(self):
+        # https://github.com/scipy/scipy/issues/9044
+        # Test the returned `OptimizeResult` contains keys consistent with
+        # other solvers.
+
+        def callback(x, info):
+            assert_('nit' in info)
+            assert_('niter' in info)
+
+        result = minimize(lambda x: x**2, [0], jac=lambda x: 2*x,
+                          hess=lambda x: 2, callback=callback,
+                          method='trust-constr')
+        assert_(result.get('success'))
+        assert_(result.get('nit', -1) == 1)
+
+        # Also check existence of the 'niter' attribute, for backward
+        # compatibility
+        assert_(result.get('niter', -1) == 1)
+
+    def test_issue_15093(self):
+        # scipy docs define bounds as inclusive, so it shouldn't be
+        # an issue to set x0 on the bounds even if keep_feasible is
+        # True. Previously, trust-constr would treat bounds as
+        # exclusive.
+
+        x0 = np.array([0., 0.5])
+
+        def obj(x):
+            x1 = x[0]
+            x2 = x[1]
+            return x1 ** 2 + x2 ** 2
+
+        bounds = Bounds(np.array([0., 0.]), np.array([1., 1.]),
+                        keep_feasible=True)
+
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "delta_grad == 0.0")
+            result = minimize(
+                method='trust-constr',
+                fun=obj,
+                x0=x0,
+                bounds=bounds)
+
+        assert result['success']
+
+class TestEmptyConstraint:
+    """
+    Here we minimize x^2+y^2 subject to x^2-y^2>1.
+    The actual minimum is at (0, 0) which fails the constraint.
+    Therefore we will find a minimum on the boundary at (+/-1, 0).
+
+    When minimizing on the boundary, optimize uses a set of
+    constraints that removes the constraint that sets that
+    boundary.  In our case, there's only one constraint, so
+    the result is an empty constraint.
+
+    This tests that the empty constraint works.
+    """
+    def test_empty_constraint(self):
+
+        def function(x):
+            return x[0]**2 + x[1]**2
+
+        def functionjacobian(x):
+            return np.array([2.*x[0], 2.*x[1]])
+
+        def functionhvp(x, v):
+            return 2.*v
+
+        def constraint(x):
+            return np.array([x[0]**2 - x[1]**2])
+
+        def constraintjacobian(x):
+            return np.array([[2*x[0], -2*x[1]]])
+
+        def constraintlcoh(x, v):
+            return np.array([[2., 0.], [0., -2.]]) * v[0]
+
+        constraint = NonlinearConstraint(constraint, 1., np.inf,
+                                         constraintjacobian, constraintlcoh)
+
+        startpoint = [1., 2.]
+
+        bounds = Bounds([-np.inf, -np.inf], [np.inf, np.inf])
+
+        result = minimize(
+          function,
+          startpoint,
+          method='trust-constr',
+          jac=functionjacobian,
+          hessp=functionhvp,
+          constraints=[constraint],
+          bounds=bounds,
+        )
+
+        assert_array_almost_equal(abs(result.x), np.array([1, 0]), decimal=4)
+
+
+def test_bug_11886():
+    def opt(x):
+        return x[0]**2+x[1]**2
+
+    with np.testing.suppress_warnings() as sup:
+        sup.filter(PendingDeprecationWarning)
+        A = np.matrix(np.diag([1, 1]))
+    lin_cons = LinearConstraint(A, -1, np.inf)
+    # just checking that there are no errors
+    minimize(opt, 2*[1], constraints = lin_cons)
+
+
+def test_gh11649():
+    # trust - constr error when attempting to keep bound constrained solutions
+    # feasible. Algorithm attempts to go outside bounds when evaluating finite
+    # differences. (don't give objective an analytic gradient)
+    bnds = Bounds(lb=[-1, -1], ub=[1, 1], keep_feasible=True)
+
+    def assert_inbounds(x):
+        assert np.all(x >= bnds.lb)
+        assert np.all(x <= bnds.ub)
+
+    def obj(x):
+        assert_inbounds(x)
+        return np.exp(x[0])*(4*x[0]**2 + 2*x[1]**2 + 4*x[0]*x[1] + 2*x[1] + 1)
+
+    def nce(x):
+        assert_inbounds(x)
+        return x[0]**2 + x[1]
+
+    def nce_jac(x):
+        return np.array([2*x[0], 1])
+
+    def nci(x):
+        assert_inbounds(x)
+        return x[0]*x[1]
+
+    x0 = np.array((0.99, -0.99))
+    nlcs = [NonlinearConstraint(nci, -10, np.inf),
+            NonlinearConstraint(nce, 1, 1, jac=nce_jac)]
+
+    res = minimize(fun=obj, x0=x0, method='trust-constr',
+                   bounds=bnds, constraints=nlcs)
+    assert_inbounds(res.x)
+    assert nlcs[0].lb < nlcs[0].fun(res.x) < nlcs[0].ub
+
+
+def test_gh20665_too_many_constraints():
+    # gh-20665 reports a confusing error message when there are more equality
+    # constraints than variables. Check that the error message is improved.
+    message = "...more equality constraints than independent variables..."
+    with pytest.raises(ValueError, match=message):
+        x0 = np.ones((2,))
+        A_eq, b_eq = np.arange(6).reshape((3, 2)), np.ones((3,))
+        g = NonlinearConstraint(lambda x:  A_eq @ x, lb=b_eq, ub=b_eq)
+        minimize(rosen, x0, method='trust-constr', constraints=[g])
+    # no error with `SVDFactorization`
+    with np.testing.suppress_warnings() as sup:
+        sup.filter(UserWarning)
+        minimize(rosen, x0, method='trust-constr', constraints=[g],
+                 options={'factorization_method': 'SVDFactorization'})
+
+def test_issue_18882():
+    def lsf(u):
+        u1, u2 = u
+        a, b = [3.0, 4.0]
+        return 1.0 + u1**2 / a**2 - u2**2 / b**2
+
+    def of(u):
+        return np.sum(u**2)
+
+    with suppress_warnings() as sup:
+        sup.filter(UserWarning, "delta_grad == 0.0")
+        sup.filter(UserWarning, "Singular Jacobian matrix.")
+        res = minimize(
+            of,
+            [0.0, 0.0],
+            method="trust-constr",
+            constraints=NonlinearConstraint(lsf, 0, 0),
+        )
+    assert (not res.success) and (res.constr_violation > 1e-8)
+
+class TestBoundedNelderMead:
+
+    @pytest.mark.parametrize('bounds, x_opt',
+                             [(Bounds(-np.inf, np.inf), Rosenbrock().x_opt),
+                              (Bounds(-np.inf, -0.8), [-0.8, -0.8]),
+                              (Bounds(3.0, np.inf), [3.0, 9.0]),
+                              (Bounds([3.0, 1.0], [4.0, 5.0]), [3., 5.]),
+                              ])
+    def test_rosen_brock_with_bounds(self, bounds, x_opt):
+        prob = Rosenbrock()
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "Initial guess is not within "
+                                    "the specified bounds")
+            result = minimize(prob.fun, [-10, -10],
+                              method='Nelder-Mead',
+                              bounds=bounds)
+            assert np.less_equal(bounds.lb, result.x).all()
+            assert np.less_equal(result.x, bounds.ub).all()
+            assert np.allclose(prob.fun(result.x), result.fun)
+            assert np.allclose(result.x, x_opt, atol=1.e-3)
+
+    def test_equal_all_bounds(self):
+        prob = Rosenbrock()
+        bounds = Bounds([4.0, 5.0], [4.0, 5.0])
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "Initial guess is not within "
+                                    "the specified bounds")
+            result = minimize(prob.fun, [-10, 8],
+                              method='Nelder-Mead',
+                              bounds=bounds)
+            assert np.allclose(result.x, [4.0, 5.0])
+
+    def test_equal_one_bounds(self):
+        prob = Rosenbrock()
+        bounds = Bounds([4.0, 5.0], [4.0, 20.0])
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning, "Initial guess is not within "
+                                    "the specified bounds")
+            result = minimize(prob.fun, [-10, 8],
+                              method='Nelder-Mead',
+                              bounds=bounds)
+            assert np.allclose(result.x, [4.0, 16.0])
+
+    def test_invalid_bounds(self):
+        prob = Rosenbrock()
+        message = 'An upper bound is less than the corresponding lower bound.'
+        with pytest.raises(ValueError, match=message):
+            bounds = Bounds([-np.inf, 1.0], [4.0, -5.0])
+            minimize(prob.fun, [-10, 3],
+                     method='Nelder-Mead',
+                     bounds=bounds)
+
+    @pytest.mark.xfail(reason="Failing on Azure Linux and macOS builds, "
+                              "see gh-13846")
+    def test_outside_bounds_warning(self):
+        prob = Rosenbrock()
+        message = "Initial guess is not within the specified bounds"
+        with pytest.warns(UserWarning, match=message):
+            bounds = Bounds([-np.inf, 1.0], [4.0, 5.0])
+            minimize(prob.fun, [-10, 8],
+                     method='Nelder-Mead',
+                     bounds=bounds)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_nnls.py

@@ -0,0 +1,469 @@
+import numpy as np
+from numpy.testing import assert_allclose
+from pytest import raises as assert_raises
+from scipy.optimize import nnls
+import pytest
+
+
+class TestNNLS:
+    def setup_method(self):
+        self.rng = np.random.default_rng(1685225766635251)
+
+    def test_nnls(self):
+        a = np.arange(25.0).reshape(-1, 5)
+        x = np.arange(5.0)
+        y = a @ x
+        x, res = nnls(a, y)
+        assert res < 1e-7
+        assert np.linalg.norm((a @ x) - y) < 1e-7
+
+    def test_nnls_tall(self):
+        a = self.rng.uniform(low=-10, high=10, size=[50, 10])
+        x = np.abs(self.rng.uniform(low=-2, high=2, size=[10]))
+        x[::2] = 0
+        b = a @ x
+        xact, rnorm = nnls(a, b)
+        assert_allclose(xact, x, rtol=0., atol=1e-10)
+        assert rnorm < 1e-12
+
+    def test_nnls_wide(self):
+        # If too wide then problem becomes too ill-conditioned ans starts
+        # emitting warnings, hence small m, n difference.
+        a = self.rng.uniform(low=-10, high=10, size=[100, 120])
+        x = np.abs(self.rng.uniform(low=-2, high=2, size=[120]))
+        x[::2] = 0
+        b = a @ x
+        xact, rnorm = nnls(a, b)
+        assert_allclose(xact, x, rtol=0., atol=1e-10)
+        assert rnorm < 1e-12
+
+    def test_maxiter(self):
+        # test that maxiter argument does stop iterations
+        a = self.rng.uniform(size=(5, 10))
+        b = self.rng.uniform(size=5)
+        with assert_raises(RuntimeError):
+            nnls(a, b, maxiter=1)
+
+    def test_nnls_inner_loop_case1(self):
+        # See gh-20168
+        n = np.array(
+            [3, 2, 0, 1, 1, 1, 3, 8, 14, 16, 29, 23, 41, 47, 53, 57, 67, 76,
+             103, 89, 97, 94, 85, 95, 78, 78, 78, 77, 73, 50, 50, 56, 68, 98,
+             95, 112, 134, 145, 158, 172, 213, 234, 222, 215, 216, 216, 206,
+             183, 135, 156, 110, 92, 63, 60, 52, 29, 20, 16, 12, 5, 5, 5, 1, 2,
+             3, 0, 2])
+        k = np.array(
+            [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
+             0., 0., 0., 0.7205812007860187, 0., 1.4411624015720375,
+             0.7205812007860187, 2.882324803144075, 5.76464960628815,
+             5.76464960628815, 12.249880413362318, 15.132205216506394,
+             20.176273622008523, 27.382085629868712, 48.27894045266326,
+             47.558359251877235, 68.45521407467177, 97.99904330689854,
+             108.0871801179028, 135.46926574777152, 140.51333415327366,
+             184.4687874012208, 171.49832578707245, 205.36564222401535,
+             244.27702706646033, 214.01261663344755, 228.42424064916793,
+             232.02714665309804, 205.36564222401535, 172.9394881886445,
+             191.67459940908097, 162.1307701768542, 153.48379576742198,
+             110.96950492104689, 103.04311171240067, 86.46974409432225,
+             60.528820866025576, 43.234872047161126, 23.779179625938617,
+             24.499760826724636, 17.29394881886445, 11.5292992125763,
+             5.76464960628815, 5.044068405502131, 3.6029060039300935, 0.,
+             2.882324803144075, 0., 0., 0.])
+        d = np.array(
+            [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
+             0., 0., 0., 0.003889242101538, 0., 0.007606268390096, 0.,
+             0.025457371599973, 0.036952882091577, 0., 0.08518359183449,
+             0.048201126400243, 0.196234990022205, 0.144116240157247,
+             0.171145134062442, 0., 0., 0.269555036538714, 0., 0., 0.,
+             0.010893241091872, 0., 0., 0., 0., 0., 0., 0., 0.,
+             0.048167058272886, 0.011238724891049, 0., 0., 0.055162603456078,
+             0., 0., 0., 0., 0.027753339088588, 0., 0., 0., 0., 0., 0., 0., 0.,
+             0., 0.])
+        # The following code sets up a system of equations such that
+        # $k_i-p_i*n_i$ is minimized for $p_i$ with weights $n_i$ and
+        # monotonicity constraints on $p_i$. This translates to a system of
+        # equations of the form $k_i - (d_1 + ... + d_i) * n_i$ and
+        # non-negativity constraints on the $d_i$. If $n_i$ is zero the
+        # system is modified such that $d_i - d_{i+1}$ is then minimized.
+        N = len(n)
+        A = np.diag(n) @ np.tril(np.ones((N, N)))
+        w = n ** 0.5
+
+        nz = (n == 0).nonzero()[0]
+        A[nz, nz] = 1
+        A[nz, np.minimum(nz + 1, N - 1)] = -1
+        w[nz] = 1
+        k[nz] = 0
+        W = np.diag(w)
+
+        # Small perturbations can already make the infinite loop go away (just
+        # uncomment the next line)
+        # k = k + 1e-10 * np.random.normal(size=N)
+        dact, _ = nnls(W @ A, W @ k)
+        assert_allclose(dact, d, rtol=0., atol=1e-10)
+
+    def test_nnls_inner_loop_case2(self):
+        # See gh-20168
+        n = np.array(
+            [1, 0, 1, 2, 2, 2, 3, 3, 5, 4, 14, 14, 19, 26, 36, 42, 36, 64, 64,
+             64, 81, 85, 85, 95, 95, 95, 75, 76, 69, 81, 62, 59, 68, 64, 71, 67,
+             74, 78, 118, 135, 153, 159, 210, 195, 218, 243, 236, 215, 196, 175,
+             185, 149, 144, 103, 104, 75, 56, 40, 32, 26, 17, 9, 12, 8, 2, 1, 1,
+             1])
+        k = np.array(
+            [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
+             0., 0., 0., 0., 0., 0.7064355064917867, 0., 0., 2.11930651947536,
+             0.7064355064917867, 0., 3.5321775324589333, 7.064355064917867,
+             11.302968103868587, 16.95445215580288, 20.486629688261814,
+             20.486629688261814, 37.44108184406469, 55.808405012851146,
+             78.41434122058831, 103.13958394780086, 105.965325973768,
+             125.74552015553803, 149.057891869767, 176.60887662294667,
+             197.09550631120848, 211.930651947536, 204.86629688261814,
+             233.8301526487814, 221.1143135319292, 195.6826352982249,
+             197.80194181770025, 191.4440222592742, 187.91184472681525,
+             144.11284332432447, 131.39700420747232, 116.5618585711448,
+             93.24948685691584, 89.01087381796512, 53.68909849337579,
+             45.211872415474346, 31.083162285638615, 24.72524272721253,
+             16.95445215580288, 9.890097090885014, 9.890097090885014,
+             2.8257420259671466, 2.8257420259671466, 1.4128710129835733,
+             0.7064355064917867, 1.4128710129835733])
+        d = np.array(
+            [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
+             0., 0., 0., 0., 0., 0.0021916146355674473, 0., 0.,
+             0.011252740799789484, 0., 0., 0.037746623295934395,
+             0.03602328132946222, 0.09509167709829734, 0.10505765870204821,
+             0.01391037014274718, 0.0188296228752321, 0.20723559202324254,
+             0.3056220879462608, 0.13304643490426477, 0., 0., 0., 0., 0., 0.,
+             0., 0., 0., 0., 0., 0.043185876949706214, 0.0037266261379722554,
+             0., 0., 0., 0., 0., 0.094797899357143, 0., 0., 0., 0., 0., 0., 0.,
+             0., 0.23450935613672663, 0., 0., 0.07064355064917871])
+        # The following code sets up a system of equations such that
+        # $k_i-p_i*n_i$ is minimized for $p_i$ with weights $n_i$ and
+        # monotonicity constraints on $p_i$. This translates to a system of
+        # equations of the form $k_i - (d_1 + ... + d_i) * n_i$ and
+        # non-negativity constraints on the $d_i$. If $n_i$ is zero the
+        # system is modified such that $d_i - d_{i+1}$ is then minimized.
+        N = len(n)
+        A = np.diag(n) @ np.tril(np.ones((N, N)))
+        w = n ** 0.5
+
+        nz = (n == 0).nonzero()[0]
+        A[nz, nz] = 1
+        A[nz, np.minimum(nz + 1, N - 1)] = -1
+        w[nz] = 1
+        k[nz] = 0
+        W = np.diag(w)
+
+        dact, _ = nnls(W @ A, W @ k)
+
+        p = np.cumsum(dact)
+        assert np.all(dact >= 0)
+        assert np.linalg.norm(k - n * p, ord=np.inf) < 28
+        assert_allclose(dact, d, rtol=0., atol=1e-10)
+
+    def test_nnls_gh20302(self):
+        # See gh-20302
+        A = np.array(
+            [0.33408569134321575, 0.11136189711440525, 0.049140798007949286,
+             0.03712063237146841, 0.055680948557202625, 0.16642814595936478,
+             0.11095209730624318, 0.09791993030943345, 0.14793612974165757,
+             0.44380838922497273, 0.11099502671044059, 0.11099502671044059,
+             0.14693672599330593, 0.3329850801313218, 1.498432860590948,
+             0.0832374225132955, 0.11098323001772734, 0.19589481249472837,
+             0.5919105600945457, 3.5514633605672747, 0.06658716751427037,
+             0.11097861252378394, 0.24485832778293645, 0.9248217710315328,
+             6.936163282736496, 0.05547609388181014, 0.11095218776362029,
+             0.29376003042571264, 1.3314262531634435, 11.982836278470993,
+             0.047506113282944136, 0.11084759766020298, 0.3423969672933396,
+             1.8105107617833156, 19.010362998724812, 0.041507335004505576,
+             0.11068622667868154, 0.39074115283013344, 2.361306169145206,
+             28.335674029742474, 0.03682846280947718, 0.11048538842843154,
+             0.4387861797121048, 2.9831054875676517, 40.2719240821633,
+             0.03311278164362387, 0.11037593881207958, 0.4870572300443105,
+             3.6791979604026523, 55.187969406039784, 0.030079304092299915,
+             0.11029078167176636, 0.5353496017200152, 4.448394860761242,
+             73.3985152025605, 0.02545939709595835, 0.11032405408248619,
+             0.6328767609778363, 6.214921713313388, 121.19097340961108,
+             0.022080881724881523, 0.11040440862440762, 0.7307742886903428,
+             8.28033064683057, 186.30743955368786, 0.020715838214945492,
+             0.1104844704797093, 0.7800578384588346, 9.42800814760186,
+             226.27219554244465, 0.01843179728340054, 0.11059078370040323,
+             0.8784095015912599, 11.94380463964355, 322.48272527037585,
+             0.015812787653789077, 0.11068951357652354, 1.0257259848595766,
+             16.27135849574896, 512.5477926160922, 0.014438550529330062,
+             0.11069555405819713, 1.1234754801775881, 19.519316032262093,
+             673.4164031130423, 0.012760770585072577, 0.110593345070629,
+             1.2688431112524712, 24.920367089248398, 971.8943164806875,
+             0.011427556646114315, 0.11046638091243838, 1.413623342459821,
+             30.967408782453557, 1347.0822820367298, 0.010033330264470307,
+             0.11036663290917338, 1.6071533470570285, 40.063087746029936,
+             1983.122843428482, 0.008950061496507258, 0.11038409179025618,
+             1.802244865119193, 50.37194055362024, 2795.642700725923,
+             0.008071078821135658, 0.11030474388885401, 1.9956465761433504,
+             61.80742482572119, 3801.1566267818534, 0.007191031207777556,
+             0.11026247851925586, 2.238160187262168, 77.7718015155818,
+             5366.2543045751445, 0.00636834224248, 0.11038459886965334,
+             2.5328963107984297, 99.49331844784753, 7760.4788389321075,
+             0.005624259098118485, 0.11061042892966355, 2.879742607664547,
+             128.34496770138628, 11358.529641572684, 0.0050354270614989555,
+             0.11077939535297703, 3.2263279459292575, 160.85168205252265,
+             15924.316523199741, 0.0044997853165982555, 0.1109947044760903,
+             3.6244287189055613, 202.60233390369015, 22488.859063309606,
+             0.004023601950058174, 0.1113196539516095, 4.07713905729421,
+             255.6270320242126, 31825.565487014468, 0.0036024117873727094,
+             0.111674765408554, 4.582933773135057, 321.9583486728612,
+             44913.18963986413, 0.003201503089582304, 0.11205260813538065,
+             5.191786833370116, 411.79333489752383, 64857.45024636,
+             0.0028633044552448853, 0.11262330857296549, 5.864295861648949,
+             522.7223161899905, 92521.84996562831, 0.0025691897303891965,
+             0.11304434813712465, 6.584584405106342, 656.5615739804199,
+             129999.19164812315, 0.0022992911894424675, 0.11343169867916175,
+             7.4080129906658305, 828.2026426227864, 183860.98666225857,
+             0.0020449922071108764, 0.11383789952917212, 8.388975556433872,
+             1058.2750599896935, 265097.9025274183, 0.001831274615120854,
+             0.11414945100919989, 9.419351803810935, 1330.564050780237,
+             373223.2162438565, 0.0016363333454631633, 0.11454333418242145,
+             10.6143816579462, 1683.787012481595, 530392.9089317025,
+             0.0014598610433380044, 0.11484240207592301, 11.959688127956882,
+             2132.0874753402027, 754758.9662704318, 0.0012985240015312626,
+             0.11513579480243862, 13.514425358573531, 2715.5160990137824,
+             1083490.9235064993, 0.0011614735761289934, 0.11537304189548002,
+             15.171418602667567, 3415.195870828736, 1526592.554260445,
+             0.0010347472698811352, 0.11554677847006009, 17.080800985009617,
+             4322.412404600832, 2172012.2333119176, 0.0009232988811258664,
+             0.1157201264344419, 19.20004861829407, 5453.349531598553,
+             3075689.135821584, 0.0008228871862975205, 0.11602709326795038,
+             21.65735242414206, 6920.203923780365, 4390869.389638642,
+             0.00073528900066722, 0.11642075843897651, 24.40223571298994,
+             8755.811207598026, 6238515.485413593, 0.0006602764384729194,
+             0.11752920604817965, 27.694443541914293, 11171.386093291572,
+             8948280.260726549, 0.0005935538977939806, 0.11851292825953147,
+             31.325508920763063, 14174.185724149384, 12735505.873148222,
+             0.0005310755355633124, 0.11913794514470308, 35.381052949627765,
+             17987.010118815077, 18157886.71494382, 0.00047239949671590953,
+             0.1190446731724092, 39.71342528048061, 22679.438775422022,
+             25718483.571328573, 0.00041829129789387623, 0.11851586773659825,
+             44.45299332965028, 28542.57147989741, 36391778.63686921,
+             0.00037321512015419886, 0.11880681324908665, 50.0668539579632,
+             36118.26128449941, 51739409.29004541, 0.0003315539616702064,
+             0.1184752823034871, 56.04387059062639, 45383.29960621684,
+             72976345.76679668, 0.00029456064937920213, 0.11831519416731286,
+             62.91195073220101, 57265.53993693082, 103507463.43600245,
+             0.00026301867496859703, 0.11862142241083726, 70.8217262087034,
+             72383.14781936012, 146901598.49939138, 0.00023618734450420032,
+             0.11966825454879482, 80.26535457124461, 92160.51176984518,
+             210125966.835247, 0.00021165918071578316, 0.12043407382728061,
+             90.7169587544247, 116975.56852918258, 299515943.218972,
+             0.00018757727511329545, 0.11992440455576689, 101.49899864101785,
+             147056.26174166967, 423080865.0307836, 0.00016654469159895833,
+             0.11957908856805206, 113.65970431102812, 184937.67016486943,
+             597533612.3026931, 0.00014717439179415048, 0.11872067604728138,
+             126.77899683346702, 231758.58906776624, 841283678.3159915,
+             0.00012868496382376066, 0.1166314722122684, 139.93635237349534,
+             287417.30847929465, 1172231492.6328032, 0.00011225559452625302,
+             0.11427619522772557, 154.0034283704458, 355281.4912295324,
+             1627544511.322488, 9.879511142981067e-05, 0.11295574406808354,
+             170.96532050841535, 442971.0111288653, 2279085852.2580123,
+             8.71257780313587e-05, 0.11192758284428547, 190.35067416684697,
+             554165.2523674504, 3203629323.93623, 7.665069027765277e-05,
+             0.11060694607065294, 211.28835951100046, 690933.608546013,
+             4486577387.093535, 6.734021094824451e-05, 0.10915848194710433,
+             234.24338803525194, 860487.9079859136, 6276829044.8032465,
+             5.9191625040287665e-05, 0.10776821865668373, 259.7454711820425,
+             1071699.0387579766, 8780430224.544102, 5.1856803674907676e-05,
+             0.10606444911641115, 287.1843540288165, 1331126.3723998806,
+             12251687131.5685, 4.503421404759231e-05, 0.10347361247668461,
+             314.7338642485931, 1638796.0697522392, 16944331963.203278,
+             3.90470387455642e-05, 0.1007804070023012, 344.3427560918527,
+             2014064.4865519698, 23392351979.057854, 3.46557661636393e-05,
+             0.10046706610839032, 385.56603915081587, 2533036.2523656,
+             33044724430.235435, 3.148745865254635e-05, 0.1025441570117926,
+             442.09038234164746, 3262712.3882769793, 47815050050.199135,
+             2.9790762078715404e-05, 0.1089845379379672, 527.8068231298969,
+             4375751.903321453, 72035815708.42941, 2.8772639817606534e-05,
+             0.11823636789048445, 643.2048194503195, 5989838.001888927,
+             110764084330.93005, 2.7951691815106586e-05, 0.12903432664913705,
+             788.5500418523591, 8249371.000613411, 171368308481.2427,
+             2.6844392423114212e-05, 0.1392060709754626, 955.6296403631383,
+             11230229.319931043, 262063016295.25085, 2.499458273851386e-05,
+             0.14559344445184325, 1122.7022399726002, 14820229.698461473,
+             388475270970.9214, 2.337386729019776e-05, 0.15294300496886065,
+             1324.8158105672455, 19644861.137128454, 578442936182.7473,
+             2.0081014872174113e-05, 0.14760215298210377, 1436.2385042492353,
+             23923681.729276657, 791311658718.4193, 1.773374462991839e-05,
+             0.14642752940923615, 1600.5596278736678, 29949429.82503553,
+             1112815989293.9326, 1.5303115839590797e-05, 0.14194150045081785,
+             1742.873058605698, 36634451.931305364, 1529085389160.7544,
+             1.3148448731163076e-05, 0.13699368732998807, 1889.5284359054356,
+             44614279.74469635, 2091762812969.9607, 1.1739194407590062e-05,
+             0.13739553134643406, 2128.794599579694, 56462810.11822766,
+             2973783283306.8145, 1.0293367506254706e-05, 0.13533033372723272,
+             2355.372854690074, 70176508.28667311, 4151852759764.441,
+             9.678312586863569e-06, 0.14293577249119244, 2794.531827932675,
+             93528671.31952812, 6215821967224.52, -1.174086323572049e-05,
+             0.1429501325944908, 3139.4804810720925, 118031680.16618933,
+             -6466892421886.174, -2.1188265307407812e-05, 0.1477108290912869,
+             3644.1133424610953, 153900132.62392554, -4828013117542.036,
+             -8.614483025123122e-05, 0.16037100755883044, 4444.386620899393,
+             210846007.89660168, -1766340937974.433, 4.981445776141726e-05,
+             0.16053420251962536, 4997.558254401547, 266327328.4755411,
+             3862250287024.725, 1.8500019169456637e-05, 0.15448417164977674,
+             5402.289867444643, 323399508.1475582, 12152445411933.408,
+             -5.647882376069748e-05, 0.1406372975946189, 5524.633133597753,
+             371512945.9909363, -4162951345292.1514, 2.8048523486337994e-05,
+             0.13183417571186926, 5817.462495763679, 439447252.3728975,
+             9294740538175.03]).reshape(89, 5)
+        b = np.ones(89, dtype=np.float64)
+        sol, rnorm = nnls(A, b)
+        assert_allclose(sol, np.array([0.61124315, 8.22262829, 0., 0., 0.]))
+        assert_allclose(rnorm, 1.0556460808977297)
+
+    def test_nnls_gh21021_ex1(self):
+        # Review examples used in gh-21021
+        A = [[0.004734199143798789, -0.09661916455815653, -0.04308779048103441,
+             0.4039475561867938, -0.27742598780954364, -0.20816924034369574,
+             -0.17264070902176, 0.05251808558963846],
+             [-0.030263548855047975, -0.30356483926431466, 0.18080406600591398,
+              -0.06892233941254086, -0.41837298885432317, 0.30245352819647003,
+              -0.19008975278116397, -0.00990809825429995],
+             [-0.2561747595787612, -0.04376282125249583, 0.4422181991706678,
+              -0.13720906318924858, -0.0069523811763796475, -0.059238287107464795,
+              0.028663214369642594, 0.5415531284893763],
+             [0.2949336072968401, 0.33997647534935094, 0.38441519339815755,
+              -0.306001783010386, 0.18120773805949028, -0.36669767490747895,
+              -0.021539960590992304, -0.2784251712424615],
+             [0.5009075736232653, -0.20161970347571165, 0.08404512586550646,
+              0.2520496489348788, 0.14812015101612894, -0.25823455803981266,
+              -0.1596872058396596, 0.5960141613922691]
+             ]
+        b = [18.036779281222124, -18.126530733870887, 13.535652034584029,
+             -2.6654275476795966, 9.166315328199575]
+
+        # Obtained from matlab's lstnonneg
+        des_sol = np.array([0., 118.017802006619, 45.1996532316584, 102.62156313537,
+                            0., 55.8590204314398, 0., 29.7328833253434])
+        sol, res = nnls(A, b)
+        assert_allclose(sol, des_sol)
+        assert np.abs(np.linalg.norm(A@sol - b) - res) < 5e-14
+
+    def test_nnls_gh21021_ex2(self):
+        A = np.array([
+            [0.2508259992635229, -0.24031300195203256],
+            [0.510647748500133, 0.2872936081767836],
+            [0.8196387904102849, -0.03520620107046682],
+            [0.030739759120097084, -0.07768656359879388]])
+        b = np.array([24.456141951303913,
+                      28.047143273432333,
+                      41.10526799545987,
+                      -1.2078282698324068])
+
+        sol, res = nnls(A, b)
+        assert_allclose(sol, np.array([54.3047953202271, 0.0]))
+        assert np.abs(np.linalg.norm(A@sol - b) - res) < 5e-14
+
+    def test_nnls_gh21021_ex3(self):
+        A = np.array([
+            [0.08247592017366788, 0.058398241636675674, -0.1031496693415968,
+             0.03156983127072098, -0.029503680182026665],
+            [0.21463607509982277, -0.2164518969308173, -0.10816833396662294,
+             0.12133867146012027, -0.15025010408668332],
+            [0.07251900316494089, -0.003044559315020767, 0.042682817961676424,
+             -0.018157525489298176, 0.11561953260568134],
+            [0.2328797918159187, -0.09112909645892767, 0.21348169727099078,
+             0.00449447624089599, -0.16615256386885716],
+            [-0.02440856024843897, -0.20131427208575386, 0.030275781997161483,
+             -0.04560777213546784, 0.11007266012013553],
+            [-0.2928391429686263, -0.20437574856615687, -0.020892110811574407,
+             -0.10455040720819309, 0.05337267000160461],
+            [0.22041503019400316, 0.014262782992311842, 0.08274606359871121,
+             -0.17933172096518907, -0.11809690350702161],
+            [0.10440436007469953, 0.09171452270577712, 0.03942347724809893,
+             0.11457669688231396, 0.07529747295631585],
+            [-0.052087576116032056, -0.15787717158077047, -0.08232202515883282,
+             -0.03194837933710708, -0.0546812506025729],
+            [-0.010388407673304468, 0.015174707581808923, 0.04764509565386281,
+             -0.1781221936030805, 0.10218894080536609],
+            [0.03272263140115928, -0.27576456949442574, 0.024897570959901753,
+             -0.1417129166632282, -0.03320796462136591],
+            [-0.12490006751823997, -0.03012003515442302, -0.051495264012509506,
+             0.012070729698374614, 0.04811700123118234],
+            [0.15254854117990788, -0.051863547789218374, 0.058012914127346174,
+             -0.06717991061422621, -0.14514671564242257],
+            [0.12251250415395559, -0.17462495626695362, -0.025334728552179834,
+             0.11425350676877533, 0.06183915953812639],
+            [0.19334259720491218, 0.2164301986218955, -0.018882278726614483,
+             0.07950236716817938, -0.2220529357431092],
+            [-0.01822205701890852, 0.12630444976752267, -0.03118092027244001,
+             0.02773743885242581, 0.06444433740044248],
+            [0.13344116850581977, -0.05142877469996826, 0.3385702016705455,
+             -0.25814970787123004, 0.2679034842977378],
+            [0.1309747058619377, 0.12090608957940627, -0.13957978654106512,
+             0.17048819760322642, -0.241775259969348],
+            [0.28613102173467275, -0.47153463906732174, 0.20359970518269746,
+             -0.0962095202871843, -0.07703076550836387],
+            [0.2212788380372723, 0.02569245145758152, -0.021596152392209966,
+             0.04610005150029433, -0.2024454395619734],
+            [-0.043225338359410316, 0.17816095186290315, -0.014709092962616079,
+             0.06993970293287989, -0.09033722782555903],
+            [0.17747622942563512, -0.20991014784011458, 0.06265720409894943,
+             0.0689704059061795, 0.024474319398401525],
+            [-0.1163880385601698, 0.29989570587630027, 0.033443765320984545,
+             0.008470296514656, -0.0014457113271462002],
+            [0.024375314902718406, 0.05279830705548363, 0.02691082431023144,
+             0.05265079368002343, 0.15542988147487913],
+            [-0.01855218360922308, -0.050265869142888164, 0.2567912677240452,
+             -0.2606428528561333, 0.25334396245022245]])
+
+        b = np.array([-7.876625373734849, -8.259856278691373, 3.2593082374900963,
+                      16.30170376973345, 2.311892943629045, -1.595345202555738,
+                      6.318582970536518, 3.0104212955340093, -6.286202915842167,
+                      3.6382333725029294, 1.9012066681249356, -3.932236581436514,
+                      4.4299317131740406, -1.9345885161292682, -1.4418721521970805,
+                      -2.3810103256943926, 25.853603392922526, -10.658470311610483,
+                      15.547103681119214, -1.6491066136547277, -1.1232029689817422,
+                      4.7845749463206975, 2.553803732013229, 2.0549409701753705,
+                      19.60887153608244])
+
+        sol, res = nnls(A, b)
+        assert_allclose(sol, np.array([0.0, 0.0, 76.3611306173957, 0.0, 0.0]),
+                        atol=5e-14)
+        assert np.abs(np.linalg.norm(A@sol - b) - res) < 5e-14
+
+    def test_atol_deprecation_warning(self):
+        """Test that using atol parameter triggers deprecation warning"""
+        a = np.array([[1, 0], [1, 0], [0, 1]])
+        b = np.array([2, 1, 1])
+
+        with pytest.warns(DeprecationWarning, match="{'atol'}"):
+            nnls(a, b, atol=1e-8)
+
+    def test_2D_singleton_RHS_input(self):
+        # Test that a 2D singleton RHS input is accepted
+        A = np.array([[1.0, 0.5, -1.],
+                      [1.0, 0.5, 0.0],
+                      [-1., 0.0, 1.0]])
+        b = np.array([[-1.0, 2.0, 2.0]]).T
+        x, r = nnls(A, b)
+        assert_allclose(x, np.array([1.0, 2.0, 3.0]))
+        assert_allclose(r, 0.0)
+
+    def test_2D_not_singleton_RHS_input_2(self):
+        # Test that a 2D but not a column vector RHS input is rejected
+        A = np.array([[1.0, 0.5, -1.],
+                      [1.0, 0.5, 0.0],
+                      [1.0, 0.5, 0.0],
+                      [0.0, 0.0, 1.0]])
+        b = np.ones(shape=[4, 2], dtype=np.float64)
+        with pytest.raises(ValueError, match="Expected a 1D array"):
+            nnls(A, b)
+
+    def test_gh_22791_32bit(self):
+        # Scikit-learn got hit by this problem on 32-bit arch.
+        desired = [0, 0, 1.05617285, 0, 0, 0, 0, 0.23123048, 0, 0, 0, 0.26128651]
+        rng = np.random.RandomState(42)
+        n_samples, n_features = 5, 12
+        X = rng.randn(n_samples, n_features)
+        X[:2, :] = 0
+        y = rng.randn(n_samples)
+        coef, _ = nnls(X, y)
+        assert_allclose(coef, desired)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_nonlin.py

@@ -0,0 +1,572 @@
+""" Unit tests for nonlinear solvers
+Author: Ondrej Certik
+May 2007
+"""
+from numpy.testing import assert_
+import pytest
+from functools import partial
+
+from scipy.optimize import _nonlin as nonlin, root
+from scipy.sparse import csr_array
+from numpy import diag, dot
+from numpy.linalg import inv
+import numpy as np
+import scipy
+from scipy.sparse.linalg import minres
+
+from .test_minpack import pressure_network
+
+SOLVERS = {'anderson': nonlin.anderson,
+           'diagbroyden': nonlin.diagbroyden,
+           'linearmixing': nonlin.linearmixing,
+           'excitingmixing': nonlin.excitingmixing,
+           'broyden1': nonlin.broyden1,
+           'broyden2': nonlin.broyden2,
+           'krylov': nonlin.newton_krylov}
+MUST_WORK = {'anderson': nonlin.anderson, 'broyden1': nonlin.broyden1,
+             'broyden2': nonlin.broyden2, 'krylov': nonlin.newton_krylov}
+
+# ----------------------------------------------------------------------------
+# Test problems
+# ----------------------------------------------------------------------------
+
+
+def F(x):
+    x = np.asarray(x).T
+    d = diag([3, 2, 1.5, 1, 0.5])
+    c = 0.01
+    f = -d @ x - c * float(x.T @ x) * x
+    return f
+
+
+F.xin = [1, 1, 1, 1, 1]
+F.KNOWN_BAD = {}
+F.JAC_KSP_BAD = {}
+F.ROOT_JAC_KSP_BAD = {}
+
+
+def F2(x):
+    return x
+
+
+F2.xin = [1, 2, 3, 4, 5, 6]
+F2.KNOWN_BAD = {'linearmixing': nonlin.linearmixing,
+                'excitingmixing': nonlin.excitingmixing}
+F2.JAC_KSP_BAD = {}
+F2.ROOT_JAC_KSP_BAD = {}
+
+
+def F2_lucky(x):
+    return x
+
+
+F2_lucky.xin = [0, 0, 0, 0, 0, 0]
+F2_lucky.KNOWN_BAD = {}
+F2_lucky.JAC_KSP_BAD = {}
+F2_lucky.ROOT_JAC_KSP_BAD = {}
+
+
+def F3(x):
+    A = np.array([[-2, 1, 0.], [1, -2, 1], [0, 1, -2]])
+    b = np.array([1, 2, 3.])
+    return A @ x - b
+
+
+F3.xin = [1, 2, 3]
+F3.KNOWN_BAD = {}
+F3.JAC_KSP_BAD = {}
+F3.ROOT_JAC_KSP_BAD = {}
+
+
+def F4_powell(x):
+    A = 1e4
+    return [A*x[0]*x[1] - 1, np.exp(-x[0]) + np.exp(-x[1]) - (1 + 1/A)]
+
+
+F4_powell.xin = [-1, -2]
+F4_powell.KNOWN_BAD = {'linearmixing': nonlin.linearmixing,
+                       'excitingmixing': nonlin.excitingmixing,
+                       'diagbroyden': nonlin.diagbroyden}
+# In the extreme case, it does not converge for nolinear problem solved by
+# MINRES and root problem solved by GMRES/BiCGStab/CGS/MINRES/TFQMR when using
+# Krylov method to approximate Jacobian
+F4_powell.JAC_KSP_BAD = {'minres'}
+F4_powell.ROOT_JAC_KSP_BAD = {'gmres', 'bicgstab', 'cgs', 'minres', 'tfqmr'}
+
+
+def F5(x):
+    return pressure_network(x, 4, np.array([.5, .5, .5, .5]))
+
+
+F5.xin = [2., 0, 2, 0]
+F5.KNOWN_BAD = {'excitingmixing': nonlin.excitingmixing,
+                'linearmixing': nonlin.linearmixing,
+                'diagbroyden': nonlin.diagbroyden}
+# In the extreme case, the Jacobian inversion yielded zero vector for nonlinear
+# problem solved by CGS/MINRES and it does not converge for root problem solved
+# by MINRES and when using Krylov method to approximate Jacobian
+F5.JAC_KSP_BAD = {'cgs', 'minres'}
+F5.ROOT_JAC_KSP_BAD = {'minres'}
+
+
+def F6(x):
+    x1, x2 = x
+    J0 = np.array([[-4.256, 14.7],
+                   [0.8394989, 0.59964207]])
+    v = np.array([(x1 + 3) * (x2**5 - 7) + 3*6,
+                  np.sin(x2 * np.exp(x1) - 1)])
+    return -np.linalg.solve(J0, v)
+
+
+F6.xin = [-0.5, 1.4]
+F6.KNOWN_BAD = {'excitingmixing': nonlin.excitingmixing,
+                'linearmixing': nonlin.linearmixing,
+                'diagbroyden': nonlin.diagbroyden}
+F6.JAC_KSP_BAD = {}
+F6.ROOT_JAC_KSP_BAD = {}
+
+
+# ----------------------------------------------------------------------------
+# Tests
+# ----------------------------------------------------------------------------
+
+
+class TestNonlin:
+    """
+    Check the Broyden methods for a few test problems.
+
+    broyden1, broyden2, and newton_krylov must succeed for
+    all functions. Some of the others don't -- tests in KNOWN_BAD are skipped.
+
+    """
+
+    def _check_nonlin_func(self, f, func, f_tol=1e-2):
+        # Test all methods mentioned in the class `KrylovJacobian`
+        if func == SOLVERS['krylov']:
+            for method in ['gmres', 'bicgstab', 'cgs', 'minres', 'tfqmr']:
+                if method in f.JAC_KSP_BAD:
+                    continue
+
+                x = func(f, f.xin, method=method, line_search=None,
+                         f_tol=f_tol, maxiter=200, verbose=0)
+                assert_(np.absolute(f(x)).max() < f_tol)
+
+        x = func(f, f.xin, f_tol=f_tol, maxiter=200, verbose=0)
+        assert_(np.absolute(f(x)).max() < f_tol)
+
+    def _check_root(self, f, method, f_tol=1e-2):
+        # Test Krylov methods
+        if method == 'krylov':
+            for jac_method in ['gmres', 'bicgstab', 'cgs', 'minres', 'tfqmr']:
+                if jac_method in f.ROOT_JAC_KSP_BAD:
+                    continue
+
+                res = root(f, f.xin, method=method,
+                           options={'ftol': f_tol, 'maxiter': 200,
+                                    'disp': 0,
+                                    'jac_options': {'method': jac_method}})
+                assert_(np.absolute(res.fun).max() < f_tol)
+
+        res = root(f, f.xin, method=method,
+                   options={'ftol': f_tol, 'maxiter': 200, 'disp': 0})
+        assert_(np.absolute(res.fun).max() < f_tol)
+
+    @pytest.mark.xfail
+    def _check_func_fail(self, *a, **kw):
+        pass
+
+    @pytest.mark.filterwarnings('ignore::DeprecationWarning')
+    def test_problem_nonlin(self):
+        for f in [F, F2, F2_lucky, F3, F4_powell, F5, F6]:
+            for func in SOLVERS.values():
+                if func in f.KNOWN_BAD.values():
+                    if func in MUST_WORK.values():
+                        self._check_func_fail(f, func)
+                    continue
+                self._check_nonlin_func(f, func)
+
+    @pytest.mark.filterwarnings('ignore::DeprecationWarning')
+    @pytest.mark.parametrize("method", ['lgmres', 'gmres', 'bicgstab', 'cgs',
+                                        'minres', 'tfqmr'])
+    def test_tol_norm_called(self, method):
+        # Check that supplying tol_norm keyword to nonlin_solve works
+        self._tol_norm_used = False
+
+        def local_norm_func(x):
+            self._tol_norm_used = True
+            return np.absolute(x).max()
+
+        nonlin.newton_krylov(F, F.xin, method=method, f_tol=1e-2,
+                             maxiter=200, verbose=0,
+                             tol_norm=local_norm_func)
+        assert_(self._tol_norm_used)
+
+    @pytest.mark.filterwarnings('ignore::DeprecationWarning')
+    def test_problem_root(self):
+        for f in [F, F2, F2_lucky, F3, F4_powell, F5, F6]:
+            for meth in SOLVERS:
+                if meth in f.KNOWN_BAD:
+                    if meth in MUST_WORK:
+                        self._check_func_fail(f, meth)
+                    continue
+                self._check_root(f, meth)
+
+    def test_no_convergence(self):
+        def wont_converge(x):
+            return 1e3 + x
+
+        with pytest.raises(scipy.optimize.NoConvergence):
+            nonlin.newton_krylov(wont_converge, xin=[0], maxiter=1)
+
+    def test_warnings_invalid_inner_param(self):
+        """
+        Test for ENH #21986, for behavior of `nonlin.newton_krylov`
+        Test the following scenarios:
+        1. Raise warning for invalid inner param
+        2. No warning for valid inner param
+        3. No warning for user-provided callable method
+        """
+        # This should raise exactly one warning
+        # (`inner_atol` is not valid for `minres`)
+        with pytest.warns(UserWarning,
+                          match="Please check inner method documentation"):
+            nonlin.newton_krylov(F, F.xin, method="minres", inner_atol=1e-5)
+
+        # This should not raise a warning (`minres` without `inner_atol`,
+        # but with `inner_maxiter` which is valid)
+        nonlin.newton_krylov(F, F.xin, method="minres", inner_maxiter=100,
+                             inner_callback= lambda _ : ...)
+
+        # Test newton_krylov with a user-provided callable method
+        def user_provided_callable_method_enh_21986(op, rhs, **kwargs):
+            """A dummy user-provided callable method for testing."""
+            # Return a dummy result (mimicking minres)
+            return minres(op, rhs, **kwargs)
+        # This should not raise any warnings
+        nonlin.newton_krylov(F, F.xin,
+                             method=user_provided_callable_method_enh_21986)
+
+    def test_non_inner_prefix(self):
+        with pytest.raises(ValueError,
+                           match="Unknown parameter"
+                           ):
+            # Pass a parameter without 'inner_' prefix
+            nonlin.newton_krylov(F, F.xin, method="minres", invalid_param=1e-5)
+
+
+class TestSecant:
+    """Check that some Jacobian approximations satisfy the secant condition"""
+
+    xs = [np.array([1., 2., 3., 4., 5.]),
+          np.array([2., 3., 4., 5., 1.]),
+          np.array([3., 4., 5., 1., 2.]),
+          np.array([4., 5., 1., 2., 3.]),
+          np.array([9., 1., 9., 1., 3.]),
+          np.array([0., 1., 9., 1., 3.]),
+          np.array([5., 5., 7., 1., 1.]),
+          np.array([1., 2., 7., 5., 1.]),]
+    fs = [x**2 - 1 for x in xs]
+
+    def _check_secant(self, jac_cls, npoints=1, **kw):
+        """
+        Check that the given Jacobian approximation satisfies secant
+        conditions for last `npoints` points.
+        """
+        jac = jac_cls(**kw)
+        jac.setup(self.xs[0], self.fs[0], None)
+        for j, (x, f) in enumerate(zip(self.xs[1:], self.fs[1:])):
+            jac.update(x, f)
+
+            for k in range(min(npoints, j+1)):
+                dx = self.xs[j-k+1] - self.xs[j-k]
+                df = self.fs[j-k+1] - self.fs[j-k]
+                assert_(np.allclose(dx, jac.solve(df)))
+
+            # Check that the `npoints` secant bound is strict
+            if j >= npoints:
+                dx = self.xs[j-npoints+1] - self.xs[j-npoints]
+                df = self.fs[j-npoints+1] - self.fs[j-npoints]
+                assert_(not np.allclose(dx, jac.solve(df)))
+
+    def test_broyden1(self):
+        self._check_secant(nonlin.BroydenFirst)
+
+    def test_broyden2(self):
+        self._check_secant(nonlin.BroydenSecond)
+
+    def test_broyden1_update(self):
+        # Check that BroydenFirst update works as for a dense matrix
+        jac = nonlin.BroydenFirst(alpha=0.1)
+        jac.setup(self.xs[0], self.fs[0], None)
+
+        B = np.identity(5) * (-1/0.1)
+
+        for last_j, (x, f) in enumerate(zip(self.xs[1:], self.fs[1:])):
+            df = f - self.fs[last_j]
+            dx = x - self.xs[last_j]
+            B += (df - dot(B, dx))[:, None] * dx[None, :] / dot(dx, dx)
+            jac.update(x, f)
+            assert_(np.allclose(jac.todense(), B, rtol=1e-10, atol=1e-13))
+
+    def test_broyden2_update(self):
+        # Check that BroydenSecond update works as for a dense matrix
+        jac = nonlin.BroydenSecond(alpha=0.1)
+        jac.setup(self.xs[0], self.fs[0], None)
+
+        H = np.identity(5) * (-0.1)
+
+        for last_j, (x, f) in enumerate(zip(self.xs[1:], self.fs[1:])):
+            df = f - self.fs[last_j]
+            dx = x - self.xs[last_j]
+            H += (dx - dot(H, df))[:, None] * df[None, :] / dot(df, df)
+            jac.update(x, f)
+            assert_(np.allclose(jac.todense(), inv(H), rtol=1e-10, atol=1e-13))
+
+    def test_anderson(self):
+        # Anderson mixing (with w0=0) satisfies secant conditions
+        # for the last M iterates, see [Ey]_
+        #
+        # .. [Ey] V. Eyert, J. Comp. Phys., 124, 271 (1996).
+        self._check_secant(nonlin.Anderson, M=3, w0=0, npoints=3)
+
+
+class TestLinear:
+    """Solve a linear equation;
+    some methods find the exact solution in a finite number of steps"""
+
+    def _check(self, jac, N, maxiter, complex=False, **kw):
+        np.random.seed(123)
+
+        A = np.random.randn(N, N)
+        if complex:
+            A = A + 1j*np.random.randn(N, N)
+        b = np.random.randn(N)
+        if complex:
+            b = b + 1j*np.random.randn(N)
+
+        def func(x):
+            return dot(A, x) - b
+
+        sol = nonlin.nonlin_solve(func, np.zeros(N), jac, maxiter=maxiter,
+                                  f_tol=1e-6, line_search=None, verbose=0)
+        assert_(np.allclose(dot(A, sol), b, atol=1e-6))
+
+    def test_broyden1(self):
+        # Broyden methods solve linear systems exactly in 2*N steps
+        self._check(nonlin.BroydenFirst(alpha=1.0), 20, 41, False)
+        self._check(nonlin.BroydenFirst(alpha=1.0), 20, 41, True)
+
+    def test_broyden2(self):
+        # Broyden methods solve linear systems exactly in 2*N steps
+        self._check(nonlin.BroydenSecond(alpha=1.0), 20, 41, False)
+        self._check(nonlin.BroydenSecond(alpha=1.0), 20, 41, True)
+
+    def test_anderson(self):
+        # Anderson is rather similar to Broyden, if given enough storage space
+        self._check(nonlin.Anderson(M=50, alpha=1.0), 20, 29, False)
+        self._check(nonlin.Anderson(M=50, alpha=1.0), 20, 29, True)
+
+    def test_krylov(self):
+        # Krylov methods solve linear systems exactly in N inner steps
+        self._check(nonlin.KrylovJacobian, 20, 2, False, inner_m=10)
+        self._check(nonlin.KrylovJacobian, 20, 2, True, inner_m=10)
+
+    def _check_autojac(self, A, b):
+        def func(x):
+            return A.dot(x) - b
+
+        def jac(v):
+            return A
+
+        sol = nonlin.nonlin_solve(func, np.zeros(b.shape[0]), jac, maxiter=2,
+                                  f_tol=1e-6, line_search=None, verbose=0)
+        np.testing.assert_allclose(A @ sol, b, atol=1e-6)
+        # test jac input as array -- not a function
+        sol = nonlin.nonlin_solve(func, np.zeros(b.shape[0]), A, maxiter=2,
+                                  f_tol=1e-6, line_search=None, verbose=0)
+        np.testing.assert_allclose(A @ sol, b, atol=1e-6)
+
+    def test_jac_sparse(self):
+        A = csr_array([[1, 2], [2, 1]])
+        b = np.array([1, -1])
+        self._check_autojac(A, b)
+        self._check_autojac((1 + 2j) * A, (2 + 2j) * b)
+
+    def test_jac_ndarray(self):
+        A = np.array([[1, 2], [2, 1]])
+        b = np.array([1, -1])
+        self._check_autojac(A, b)
+        self._check_autojac((1 + 2j) * A, (2 + 2j) * b)
+
+
+class TestJacobianDotSolve:
+    """
+    Check that solve/dot methods in Jacobian approximations are consistent
+    """
+
+    def _func(self, x, A=None):
+        return x**2 - 1 + np.dot(A, x)
+
+    def _check_dot(self, jac_cls, complex=False, tol=1e-6, **kw):
+        rng = np.random.RandomState(123)
+
+        N = 7
+
+        def rand(*a):
+            q = rng.rand(*a)
+            if complex:
+                q = q + 1j*rng.rand(*a)
+            return q
+
+        def assert_close(a, b, msg):
+            d = abs(a - b).max()
+            f = tol + abs(b).max()*tol
+            if d > f:
+                raise AssertionError(f'{msg}: err {d:g}')
+
+        A = rand(N, N)
+
+        # initialize
+        x0 = rng.rand(N)
+        jac = jac_cls(**kw)
+        jac.setup(x0, self._func(x0, A), partial(self._func, A=A))
+
+        # check consistency
+        for k in range(2*N):
+            v = rand(N)
+
+            if hasattr(jac, '__array__'):
+                Jd = np.array(jac)
+                if hasattr(jac, 'solve'):
+                    Gv = jac.solve(v)
+                    Gv2 = np.linalg.solve(Jd, v)
+                    assert_close(Gv, Gv2, 'solve vs array')
+                if hasattr(jac, 'rsolve'):
+                    Gv = jac.rsolve(v)
+                    Gv2 = np.linalg.solve(Jd.T.conj(), v)
+                    assert_close(Gv, Gv2, 'rsolve vs array')
+                if hasattr(jac, 'matvec'):
+                    Jv = jac.matvec(v)
+                    Jv2 = np.dot(Jd, v)
+                    assert_close(Jv, Jv2, 'dot vs array')
+                if hasattr(jac, 'rmatvec'):
+                    Jv = jac.rmatvec(v)
+                    Jv2 = np.dot(Jd.T.conj(), v)
+                    assert_close(Jv, Jv2, 'rmatvec vs array')
+
+            if hasattr(jac, 'matvec') and hasattr(jac, 'solve'):
+                Jv = jac.matvec(v)
+                Jv2 = jac.solve(jac.matvec(Jv))
+                assert_close(Jv, Jv2, 'dot vs solve')
+
+            if hasattr(jac, 'rmatvec') and hasattr(jac, 'rsolve'):
+                Jv = jac.rmatvec(v)
+                Jv2 = jac.rmatvec(jac.rsolve(Jv))
+                assert_close(Jv, Jv2, 'rmatvec vs rsolve')
+
+            x = rand(N)
+            jac.update(x, self._func(x, A))
+
+    def test_broyden1(self):
+        self._check_dot(nonlin.BroydenFirst, complex=False)
+        self._check_dot(nonlin.BroydenFirst, complex=True)
+
+    def test_broyden2(self):
+        self._check_dot(nonlin.BroydenSecond, complex=False)
+        self._check_dot(nonlin.BroydenSecond, complex=True)
+
+    def test_anderson(self):
+        self._check_dot(nonlin.Anderson, complex=False)
+        self._check_dot(nonlin.Anderson, complex=True)
+
+    def test_diagbroyden(self):
+        self._check_dot(nonlin.DiagBroyden, complex=False)
+        self._check_dot(nonlin.DiagBroyden, complex=True)
+
+    def test_linearmixing(self):
+        self._check_dot(nonlin.LinearMixing, complex=False)
+        self._check_dot(nonlin.LinearMixing, complex=True)
+
+    def test_excitingmixing(self):
+        self._check_dot(nonlin.ExcitingMixing, complex=False)
+        self._check_dot(nonlin.ExcitingMixing, complex=True)
+
+    @pytest.mark.thread_unsafe
+    def test_krylov(self):
+        self._check_dot(nonlin.KrylovJacobian, complex=False, tol=1e-3)
+        self._check_dot(nonlin.KrylovJacobian, complex=True, tol=1e-3)
+
+
+class TestNonlinOldTests:
+    """ Test case for a simple constrained entropy maximization problem
+    (the machine translation example of Berger et al in
+    Computational Linguistics, vol 22, num 1, pp 39--72, 1996.)
+    """
+
+    def test_broyden1(self):
+        x = nonlin.broyden1(F, F.xin, iter=12, alpha=1)
+        assert_(nonlin.norm(x) < 1e-9)
+        assert_(nonlin.norm(F(x)) < 1e-9)
+
+    def test_broyden2(self):
+        x = nonlin.broyden2(F, F.xin, iter=12, alpha=1)
+        assert_(nonlin.norm(x) < 1e-9)
+        assert_(nonlin.norm(F(x)) < 1e-9)
+
+    def test_anderson(self):
+        x = nonlin.anderson(F, F.xin, iter=12, alpha=0.03, M=5)
+        assert_(nonlin.norm(x) < 0.33)
+
+    def test_linearmixing(self):
+        x = nonlin.linearmixing(F, F.xin, iter=60, alpha=0.5)
+        assert_(nonlin.norm(x) < 1e-7)
+        assert_(nonlin.norm(F(x)) < 1e-7)
+
+    def test_exciting(self):
+        x = nonlin.excitingmixing(F, F.xin, iter=20, alpha=0.5)
+        assert_(nonlin.norm(x) < 1e-5)
+        assert_(nonlin.norm(F(x)) < 1e-5)
+
+    def test_diagbroyden(self):
+        x = nonlin.diagbroyden(F, F.xin, iter=11, alpha=1)
+        assert_(nonlin.norm(x) < 1e-8)
+        assert_(nonlin.norm(F(x)) < 1e-8)
+
+    def test_root_broyden1(self):
+        res = root(F, F.xin, method='broyden1',
+                   options={'nit': 12, 'jac_options': {'alpha': 1}})
+        assert_(nonlin.norm(res.x) < 1e-9)
+        assert_(nonlin.norm(res.fun) < 1e-9)
+
+    def test_root_broyden2(self):
+        res = root(F, F.xin, method='broyden2',
+                   options={'nit': 12, 'jac_options': {'alpha': 1}})
+        assert_(nonlin.norm(res.x) < 1e-9)
+        assert_(nonlin.norm(res.fun) < 1e-9)
+
+    def test_root_anderson(self):
+        res = root(F, F.xin, method='anderson',
+                   options={'nit': 12,
+                            'jac_options': {'alpha': 0.03, 'M': 5}})
+        assert_(nonlin.norm(res.x) < 0.33)
+
+    def test_root_linearmixing(self):
+        res = root(F, F.xin, method='linearmixing',
+                   options={'nit': 60,
+                            'jac_options': {'alpha': 0.5}})
+        assert_(nonlin.norm(res.x) < 1e-7)
+        assert_(nonlin.norm(res.fun) < 1e-7)
+
+    def test_root_excitingmixing(self):
+        res = root(F, F.xin, method='excitingmixing',
+                   options={'nit': 20,
+                            'jac_options': {'alpha': 0.5}})
+        assert_(nonlin.norm(res.x) < 1e-5)
+        assert_(nonlin.norm(res.fun) < 1e-5)
+
+    def test_root_diagbroyden(self):
+        res = root(F, F.xin, method='diagbroyden',
+                   options={'nit': 11,
+                            'jac_options': {'alpha': 1}})
+        assert_(nonlin.norm(res.x) < 1e-8)
+        assert_(nonlin.norm(res.fun) < 1e-8)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_quadratic_assignment.py

@@ -0,0 +1,455 @@
+import pytest
+import numpy as np
+from numpy.random import default_rng
+from scipy.optimize import quadratic_assignment, OptimizeWarning
+from scipy.optimize._qap import _calc_score as _score
+from numpy.testing import assert_equal, assert_, assert_warns
+
+
+################
+# Common Tests #
+################
+
+def chr12c():
+    A = [
+        [0, 90, 10, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+        [90, 0, 0, 23, 0, 0, 0, 0, 0, 0, 0, 0],
+        [10, 0, 0, 0, 43, 0, 0, 0, 0, 0, 0, 0],
+        [0, 23, 0, 0, 0, 88, 0, 0, 0, 0, 0, 0],
+        [0, 0, 43, 0, 0, 0, 26, 0, 0, 0, 0, 0],
+        [0, 0, 0, 88, 0, 0, 0, 16, 0, 0, 0, 0],
+        [0, 0, 0, 0, 26, 0, 0, 0, 1, 0, 0, 0],
+        [0, 0, 0, 0, 0, 16, 0, 0, 0, 96, 0, 0],
+        [0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 29, 0],
+        [0, 0, 0, 0, 0, 0, 0, 96, 0, 0, 0, 37],
+        [0, 0, 0, 0, 0, 0, 0, 0, 29, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 0, 0, 37, 0, 0],
+    ]
+    B = [
+        [0, 36, 54, 26, 59, 72, 9, 34, 79, 17, 46, 95],
+        [36, 0, 73, 35, 90, 58, 30, 78, 35, 44, 79, 36],
+        [54, 73, 0, 21, 10, 97, 58, 66, 69, 61, 54, 63],
+        [26, 35, 21, 0, 93, 12, 46, 40, 37, 48, 68, 85],
+        [59, 90, 10, 93, 0, 64, 5, 29, 76, 16, 5, 76],
+        [72, 58, 97, 12, 64, 0, 96, 55, 38, 54, 0, 34],
+        [9, 30, 58, 46, 5, 96, 0, 83, 35, 11, 56, 37],
+        [34, 78, 66, 40, 29, 55, 83, 0, 44, 12, 15, 80],
+        [79, 35, 69, 37, 76, 38, 35, 44, 0, 64, 39, 33],
+        [17, 44, 61, 48, 16, 54, 11, 12, 64, 0, 70, 86],
+        [46, 79, 54, 68, 5, 0, 56, 15, 39, 70, 0, 18],
+        [95, 36, 63, 85, 76, 34, 37, 80, 33, 86, 18, 0],
+    ]
+    A, B = np.array(A), np.array(B)
+    n = A.shape[0]
+
+    opt_perm = np.array([7, 5, 1, 3, 10, 4, 8, 6, 9, 11, 2, 12]) - [1] * n
+
+    return A, B, opt_perm
+
+
+@pytest.mark.filterwarnings("ignore:The NumPy global RNG was seeded by calling")
+class QAPCommonTests:
+    """
+    Base class for `quadratic_assignment` tests.
+    """
+    # Test global optima of problem from Umeyama IVB
+    # https://pcl.sitehost.iu.edu/rgoldsto/papers/weighted%20graph%20match2.pdf
+    # Graph matching maximum is in the paper
+    # QAP minimum determined by brute force
+    def test_accuracy_1(self):
+        # besides testing accuracy, check that A and B can be lists
+        rng = np.random.default_rng(4358764578823597324)
+
+        A = [[0, 3, 4, 2],
+             [0, 0, 1, 2],
+             [1, 0, 0, 1],
+             [0, 0, 1, 0]]
+
+        B = [[0, 4, 2, 4],
+             [0, 0, 1, 0],
+             [0, 2, 0, 2],
+             [0, 1, 2, 0]]
+
+        res = quadratic_assignment(A, B, method=self.method,
+                                   options={"rng": rng, "maximize": False})
+
+        assert_equal(res.fun, 10)
+        assert_equal(res.col_ind, np.array([1, 2, 3, 0]))
+
+        res = quadratic_assignment(A, B, method=self.method,
+                                   options={"rng": rng, "maximize": True})
+
+        if self.method == 'faq':
+            # Global optimum is 40, but FAQ gets 37
+            assert_equal(res.fun, 37)
+            assert_equal(res.col_ind, np.array([0, 2, 3, 1]))
+        else:
+            assert_equal(res.fun, 40)
+            assert_equal(res.col_ind, np.array([0, 3, 1, 2]))
+
+        quadratic_assignment(A, B, method=self.method,
+                             options={"rng": rng, "maximize": True})
+
+    # Test global optima of problem from Umeyama IIIB
+    # https://pcl.sitehost.iu.edu/rgoldsto/papers/weighted%20graph%20match2.pdf
+    # Graph matching maximum is in the paper
+    # QAP minimum determined by brute force
+    def test_accuracy_2(self):
+        rng = np.random.default_rng(4358764578823597324)
+
+        A = np.array([[0, 5, 8, 6],
+                      [5, 0, 5, 1],
+                      [8, 5, 0, 2],
+                      [6, 1, 2, 0]])
+
+        B = np.array([[0, 1, 8, 4],
+                      [1, 0, 5, 2],
+                      [8, 5, 0, 5],
+                      [4, 2, 5, 0]])
+
+        res = quadratic_assignment(A, B, method=self.method,
+                                   options={"rng": rng, "maximize": False})
+
+        if self.method == 'faq':
+            # Global optimum is 176, but FAQ gets 178
+            assert_equal(res.fun, 178)
+            assert_equal(res.col_ind, np.array([1, 0, 3, 2]))
+        else:
+            assert_equal(res.fun, 176)
+            assert_equal(res.col_ind, np.array([1, 2, 3, 0]))
+
+        res = quadratic_assignment(A, B, method=self.method,
+                                   options={"rng": rng, "maximize": True})
+
+        assert_equal(res.fun, 286)
+        assert_equal(res.col_ind, np.array([2, 3, 0, 1]))
+
+    def test_accuracy_3(self):
+        rng = np.random.default_rng(4358764578823597324)
+        A, B, opt_perm = chr12c()
+
+        # basic minimization
+        res = quadratic_assignment(A, B, method=self.method,
+                                   options={"rng": rng})
+        assert_(11156 <= res.fun < 21000)
+        assert_equal(res.fun, _score(A, B, res.col_ind))
+
+        # basic maximization
+        res = quadratic_assignment(A, B, method=self.method,
+                                   options={"rng": rng, 'maximize': True})
+        assert_(74000 <= res.fun < 85000)
+        assert_equal(res.fun, _score(A, B, res.col_ind))
+
+        # check ofv with strictly partial match
+        seed_cost = np.array([4, 8, 10])
+        seed = np.asarray([seed_cost, opt_perm[seed_cost]]).T
+        res = quadratic_assignment(A, B, method=self.method,
+                                   options={'partial_match': seed, "rng": rng})
+        assert_(11156 <= res.fun < 21000)
+        assert_equal(res.col_ind[seed_cost], opt_perm[seed_cost])
+
+        # check performance when partial match is the global optimum
+        seed = np.asarray([np.arange(len(A)), opt_perm]).T
+        res = quadratic_assignment(A, B, method=self.method,
+                                   options={'partial_match': seed, "rng": rng})
+        assert_equal(res.col_ind, seed[:, 1].T)
+        assert_equal(res.fun, 11156)
+        assert_equal(res.nit, 0)
+
+        # check performance with zero sized matrix inputs
+        empty = np.empty((0, 0))
+        res = quadratic_assignment(empty, empty, method=self.method,
+                                   options={"rng": rng})
+        assert_equal(res.nit, 0)
+        assert_equal(res.fun, 0)
+
+    @pytest.mark.thread_unsafe
+    def test_unknown_options(self):
+        A, B, opt_perm = chr12c()
+
+        def f():
+            quadratic_assignment(A, B, method=self.method,
+                                 options={"ekki-ekki": True})
+        assert_warns(OptimizeWarning, f)
+
+    @pytest.mark.thread_unsafe
+    def test_deprecation_future_warnings(self):
+        # May be removed after SPEC-7 transition is complete in SciPy 1.17
+        A = np.arange(16).reshape((4, 4))
+        B = np.arange(16).reshape((4, 4))
+
+        with pytest.warns(DeprecationWarning, match="Use of `RandomState`*"):
+            rng = np.random.RandomState(0)
+            quadratic_assignment(A, B, method=self.method,
+                                 options={"rng": rng, "maximize": False})
+
+        with pytest.warns(FutureWarning, match="The NumPy global RNG was seeded*"):
+            np.random.seed(0)
+            quadratic_assignment(A, B, method=self.method,
+                                 options={"maximize": False})
+
+        with pytest.warns(FutureWarning, match="The behavior when the rng option*"):
+            quadratic_assignment(A, B, method=self.method,
+                                 options={"rng": 0, "maximize": False})
+
+
+class TestFAQ(QAPCommonTests):
+    method = "faq"
+
+    def test_options(self):
+        # cost and distance matrices of QAPLIB instance chr12c
+        rng = np.random.default_rng(4358764578823597324)
+
+        A, B, opt_perm = chr12c()
+        n = len(A)
+
+        # check that max_iter is obeying with low input value
+        res = quadratic_assignment(A, B, options={'maxiter': 5})
+        assert_equal(res.nit, 5)
+
+        # test with shuffle
+        res = quadratic_assignment(A, B, options={'shuffle_input': True})
+        assert_(11156 <= res.fun < 21000)
+
+        # test with randomized init
+        res = quadratic_assignment(A, B, options={'rng': rng, 'P0': "randomized"})
+        assert_(11156 <= res.fun < 21000)
+
+        # check with specified P0
+        K = np.ones((n, n)) / float(n)
+        K = _doubly_stochastic(K)
+        res = quadratic_assignment(A, B, options={'P0': K})
+        assert_(11156 <= res.fun < 21000)
+
+    def test_specific_input_validation(self):
+
+        A = np.identity(2)
+        B = A
+
+        # method is implicitly faq
+
+        # ValueError Checks: making sure single value parameters are of
+        # correct value
+        with pytest.raises(ValueError, match="Invalid 'P0' parameter"):
+            quadratic_assignment(A, B, options={'P0': "random"})
+        with pytest.raises(
+                ValueError, match="'maxiter' must be a positive integer"):
+            quadratic_assignment(A, B, options={'maxiter': -1})
+        with pytest.raises(ValueError, match="'tol' must be a positive float"):
+            quadratic_assignment(A, B, options={'tol': -1})
+
+        # TypeError Checks: making sure single value parameters are of
+        # correct type
+        with pytest.raises(TypeError):
+            quadratic_assignment(A, B, options={'maxiter': 1.5})
+
+        # test P0 matrix input
+        with pytest.raises(
+                ValueError,
+                match="`P0` matrix must have shape m' x m', where m'=n-m"):
+            quadratic_assignment(
+                np.identity(4), np.identity(4),
+                options={'P0': np.ones((3, 3))}
+            )
+
+        K = [[0.4, 0.2, 0.3],
+             [0.3, 0.6, 0.2],
+             [0.2, 0.2, 0.7]]
+        # matrix that isn't quite doubly stochastic
+        with pytest.raises(
+                ValueError, match="`P0` matrix must be doubly stochastic"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3), options={'P0': K}
+            )
+
+
+class Test2opt(QAPCommonTests):
+    method = "2opt"
+
+    def test_deterministic(self):
+        n = 20
+        rng = default_rng(51982908)
+        A = rng.random(size=(n, n))
+        B = rng.random(size=(n, n))
+        res1 = quadratic_assignment(A, B, method=self.method, options={'rng': rng})
+
+        rng = default_rng(51982908)
+        A = rng.random(size=(n, n))
+        B = rng.random(size=(n, n))
+        res2 = quadratic_assignment(A, B, method=self.method, options={'rng': rng})
+
+        assert_equal(res1.nit, res2.nit)
+
+    def test_partial_guess(self):
+        n = 5
+        rng = np.random.default_rng(4358764578823597324)
+
+        A = rng.random(size=(n, n))
+        B = rng.random(size=(n, n))
+
+        res1 = quadratic_assignment(A, B, method=self.method,
+                                    options={'rng': rng})
+        guess = np.array([np.arange(5), res1.col_ind]).T
+        res2 = quadratic_assignment(A, B, method=self.method,
+                                    options={'rng': rng, 'partial_guess': guess})
+        fix = [2, 4]
+        match = np.array([np.arange(5)[fix], res1.col_ind[fix]]).T
+        res3 = quadratic_assignment(A, B, method=self.method,
+                                    options={'rng': rng, 'partial_guess': guess,
+                                             'partial_match': match})
+        assert_(res1.nit != n*(n+1)/2)
+        assert_equal(res2.nit, n*(n+1)/2)      # tests each swap exactly once
+        assert_equal(res3.nit, (n-2)*(n-1)/2)  # tests free swaps exactly once
+
+    def test_specific_input_validation(self):
+        # can't have more seed nodes than cost/dist nodes
+        _rm = _range_matrix
+        with pytest.raises(
+                ValueError,
+                match="`partial_guess` can have only as many entries as"):
+            quadratic_assignment(np.identity(3), np.identity(3),
+                                 method=self.method,
+                                 options={'partial_guess': _rm(5, 2)})
+        # test for only two seed columns
+        with pytest.raises(
+                ValueError, match="`partial_guess` must have two columns"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3), method=self.method,
+                options={'partial_guess': _range_matrix(2, 3)}
+            )
+        # test that seed has no more than two dimensions
+        with pytest.raises(
+                ValueError, match="`partial_guess` must have exactly two"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3), method=self.method,
+                options={'partial_guess': np.random.rand(3, 2, 2)}
+            )
+        # seeds cannot be negative valued
+        with pytest.raises(
+                ValueError, match="`partial_guess` must contain only pos"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3), method=self.method,
+                options={'partial_guess': -1 * _range_matrix(2, 2)}
+            )
+        # seeds can't have values greater than number of nodes
+        with pytest.raises(
+                ValueError,
+                match="`partial_guess` entries must be less than number"):
+            quadratic_assignment(
+                np.identity(5), np.identity(5), method=self.method,
+                options={'partial_guess': 2 * _range_matrix(4, 2)}
+            )
+        # columns of seed matrix must be unique
+        with pytest.raises(
+                ValueError,
+                match="`partial_guess` column entries must be unique"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3), method=self.method,
+                options={'partial_guess': np.ones((2, 2))}
+            )
+
+
+@pytest.mark.filterwarnings("ignore:The NumPy global RNG was seeded by calling")
+class TestQAPOnce:
+
+    # these don't need to be repeated for each method
+    def test_common_input_validation(self):
+        rng = default_rng(12349038)
+        # test that non square matrices return error
+        with pytest.raises(ValueError, match="`A` must be square"):
+            quadratic_assignment(
+                rng.random((3, 4)),
+                rng.random((3, 3)),
+            )
+        with pytest.raises(ValueError, match="`B` must be square"):
+            quadratic_assignment(
+                rng.random((3, 3)),
+                rng.random((3, 4)),
+            )
+        # test that cost and dist matrices have no more than two dimensions
+        with pytest.raises(
+                ValueError, match="`A` and `B` must have exactly two"):
+            quadratic_assignment(
+                rng.random((3, 3, 3)),
+                rng.random((3, 3, 3)),
+            )
+        # test that cost and dist matrices of different sizes return error
+        with pytest.raises(
+                ValueError,
+                match="`A` and `B` matrices must be of equal size"):
+            quadratic_assignment(
+                rng.random((3, 3)),
+                rng.random((4, 4)),
+            )
+        # can't have more seed nodes than cost/dist nodes
+        _rm = _range_matrix
+        with pytest.raises(
+                ValueError,
+                match="`partial_match` can have only as many seeds as"):
+            quadratic_assignment(np.identity(3), np.identity(3),
+                                 options={'partial_match': _rm(5, 2)})
+        # test for only two seed columns
+        with pytest.raises(
+                ValueError, match="`partial_match` must have two columns"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3),
+                options={'partial_match': _range_matrix(2, 3)}
+            )
+        # test that seed has no more than two dimensions
+        with pytest.raises(
+                ValueError, match="`partial_match` must have exactly two"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3),
+                options={'partial_match': np.random.rand(3, 2, 2)}
+            )
+        # seeds cannot be negative valued
+        with pytest.raises(
+                ValueError, match="`partial_match` must contain only pos"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3),
+                options={'partial_match': -1 * _range_matrix(2, 2)}
+            )
+        # seeds can't have values greater than number of nodes
+        with pytest.raises(
+                ValueError,
+                match="`partial_match` entries must be less than number"):
+            quadratic_assignment(
+                np.identity(5), np.identity(5),
+                options={'partial_match': 2 * _range_matrix(4, 2)}
+            )
+        # columns of seed matrix must be unique
+        with pytest.raises(
+                ValueError,
+                match="`partial_match` column entries must be unique"):
+            quadratic_assignment(
+                np.identity(3), np.identity(3),
+                options={'partial_match': np.ones((2, 2))}
+            )
+
+
+def _range_matrix(a, b):
+    mat = np.zeros((a, b))
+    for i in range(b):
+        mat[:, i] = np.arange(a)
+    return mat
+
+
+def _doubly_stochastic(P, tol=1e-3):
+    # cleaner implementation of btaba/sinkhorn_knopp
+
+    max_iter = 1000
+    c = 1 / P.sum(axis=0)
+    r = 1 / (P @ c)
+    P_eps = P
+
+    for it in range(max_iter):
+        if ((np.abs(P_eps.sum(axis=1) - 1) < tol).all() and
+                (np.abs(P_eps.sum(axis=0) - 1) < tol).all()):
+            # All column/row sums ~= 1 within threshold
+            break
+
+        c = 1 / (r @ P)
+        r = 1 / (P @ c)
+        P_eps = r[:, None] * P * c
+
+    return P_eps

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_regression.py

@@ -0,0 +1,40 @@
+"""Regression tests for optimize.
+
+"""
+import numpy as np
+from numpy.testing import assert_almost_equal
+from pytest import raises as assert_raises
+
+import scipy.optimize
+
+
+class TestRegression:
+
+    def test_newton_x0_is_0(self):
+        # Regression test for gh-1601
+        tgt = 1
+        res = scipy.optimize.newton(lambda x: x - 1, 0)
+        assert_almost_equal(res, tgt)
+
+    def test_newton_integers(self):
+        # Regression test for gh-1741
+        root = scipy.optimize.newton(lambda x: x**2 - 1, x0=2,
+                                    fprime=lambda x: 2*x)
+        assert_almost_equal(root, 1.0)
+
+    def test_lmdif_errmsg(self):
+        # This shouldn't cause a crash on Python 3
+        class SomeError(Exception):
+            pass
+        counter = [0]
+
+        def func(x):
+            counter[0] += 1
+            if counter[0] < 3:
+                return x**2 - np.array([9, 10, 11])
+            else:
+                raise SomeError()
+        assert_raises(SomeError,
+                      scipy.optimize.leastsq,
+                      func, [1, 2, 3])
+

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_slsqp.py

@@ -0,0 +1,645 @@
+"""
+Unit test for SLSQP optimization.
+"""
+from numpy.testing import (assert_, assert_array_almost_equal,
+                           assert_allclose, assert_equal)
+from pytest import raises as assert_raises
+import pytest
+import numpy as np
+import scipy
+
+from scipy.optimize import fmin_slsqp, minimize, Bounds, NonlinearConstraint
+
+
+class MyCallBack:
+    """pass a custom callback function
+
+    This makes sure it's being used.
+    """
+    def __init__(self):
+        self.been_called = False
+        self.ncalls = 0
+
+    def __call__(self, x):
+        self.been_called = True
+        self.ncalls += 1
+
+
+class TestSLSQP:
+    """
+    Test SLSQP algorithm using Example 14.4 from Numerical Methods for
+    Engineers by Steven Chapra and Raymond Canale.
+    This example maximizes the function f(x) = 2*x*y + 2*x - x**2 - 2*y**2,
+    which has a maximum at x=2, y=1.
+    """
+    def setup_method(self):
+        self.opts = {'disp': False}
+
+    def fun(self, d, sign=1.0):
+        """
+        Arguments:
+        d     - A list of two elements, where d[0] represents x and d[1] represents y
+                 in the following equation.
+        sign - A multiplier for f. Since we want to optimize it, and the SciPy
+               optimizers can only minimize functions, we need to multiply it by
+               -1 to achieve the desired solution
+        Returns:
+        2*x*y + 2*x - x**2 - 2*y**2
+
+        """
+        x = d[0]
+        y = d[1]
+        return sign*(2*x*y + 2*x - x**2 - 2*y**2)
+
+    def jac(self, d, sign=1.0):
+        """
+        This is the derivative of fun, returning a NumPy array
+        representing df/dx and df/dy.
+
+        """
+        x = d[0]
+        y = d[1]
+        dfdx = sign*(-2*x + 2*y + 2)
+        dfdy = sign*(2*x - 4*y)
+        return np.array([dfdx, dfdy], float)
+
+    def fun_and_jac(self, d, sign=1.0):
+        return self.fun(d, sign), self.jac(d, sign)
+
+    def f_eqcon(self, x, sign=1.0):
+        """ Equality constraint """
+        return np.array([x[0] - x[1]])
+
+    def fprime_eqcon(self, x, sign=1.0):
+        """ Equality constraint, derivative """
+        return np.array([[1, -1]])
+
+    def f_eqcon_scalar(self, x, sign=1.0):
+        """ Scalar equality constraint """
+        return self.f_eqcon(x, sign)[0]
+
+    def fprime_eqcon_scalar(self, x, sign=1.0):
+        """ Scalar equality constraint, derivative """
+        return self.fprime_eqcon(x, sign)[0].tolist()
+
+    def f_ieqcon(self, x, sign=1.0):
+        """ Inequality constraint """
+        return np.array([x[0] - x[1] - 1.0])
+
+    def fprime_ieqcon(self, x, sign=1.0):
+        """ Inequality constraint, derivative """
+        return np.array([[1, -1]])
+
+    def f_ieqcon2(self, x):
+        """ Vector inequality constraint """
+        return np.asarray(x)
+
+    def fprime_ieqcon2(self, x):
+        """ Vector inequality constraint, derivative """
+        return np.identity(x.shape[0])
+
+    # minimize
+    def test_minimize_unbounded_approximated(self):
+        # Minimize, method='SLSQP': unbounded, approximated jacobian.
+        jacs = [None, False, '2-point', '3-point']
+        for jac in jacs:
+            res = minimize(self.fun, [-1.0, 1.0], args=(-1.0, ),
+                           jac=jac, method='SLSQP',
+                           options=self.opts)
+            assert_(res['success'], res['message'])
+            assert_allclose(res.x, [2, 1])
+
+    def test_minimize_unbounded_given(self):
+        # Minimize, method='SLSQP': unbounded, given Jacobian.
+        res = minimize(self.fun, [-1.0, 1.0], args=(-1.0, ),
+                       jac=self.jac, method='SLSQP', options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_allclose(res.x, [2, 1])
+
+    def test_minimize_bounded_approximated(self):
+        # Minimize, method='SLSQP': bounded, approximated jacobian.
+        jacs = [None, False, '2-point', '3-point']
+        for jac in jacs:
+            with np.errstate(invalid='ignore'):
+                res = minimize(self.fun, [-1.0, 1.0], args=(-1.0, ),
+                               jac=jac,
+                               bounds=((2.5, None), (None, 0.5)),
+                               method='SLSQP', options=self.opts)
+            assert_(res['success'], res['message'])
+            assert_allclose(res.x, [2.5, 0.5])
+            assert_(2.5 <= res.x[0])
+            assert_(res.x[1] <= 0.5)
+
+    def test_minimize_unbounded_combined(self):
+        # Minimize, method='SLSQP': unbounded, combined function and Jacobian.
+        res = minimize(self.fun_and_jac, [-1.0, 1.0], args=(-1.0, ),
+                       jac=True, method='SLSQP', options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_allclose(res.x, [2, 1])
+
+    def test_minimize_equality_approximated(self):
+        # Minimize with method='SLSQP': equality constraint, approx. jacobian.
+        jacs = [None, False, '2-point', '3-point']
+        for jac in jacs:
+            res = minimize(self.fun, [-1.0, 1.0], args=(-1.0, ),
+                           jac=jac,
+                           constraints={'type': 'eq',
+                                        'fun': self.f_eqcon,
+                                        'args': (-1.0, )},
+                           method='SLSQP', options=self.opts)
+            assert_(res['success'], res['message'])
+            assert_allclose(res.x, [1, 1])
+
+    def test_minimize_equality_given(self):
+        # Minimize with method='SLSQP': equality constraint, given Jacobian.
+        res = minimize(self.fun, [-1.0, 1.0], jac=self.jac,
+                       method='SLSQP', args=(-1.0,),
+                       constraints={'type': 'eq', 'fun':self.f_eqcon,
+                                    'args': (-1.0, )},
+                       options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_allclose(res.x, [1, 1])
+
+    def test_minimize_equality_given2(self):
+        # Minimize with method='SLSQP': equality constraint, given Jacobian
+        # for fun and const.
+        res = minimize(self.fun, [-1.0, 1.0], method='SLSQP',
+                       jac=self.jac, args=(-1.0,),
+                       constraints={'type': 'eq',
+                                    'fun': self.f_eqcon,
+                                    'args': (-1.0, ),
+                                    'jac': self.fprime_eqcon},
+                       options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_allclose(res.x, [1, 1])
+
+    def test_minimize_equality_given_cons_scalar(self):
+        # Minimize with method='SLSQP': scalar equality constraint, given
+        # Jacobian for fun and const.
+        res = minimize(self.fun, [-1.0, 1.0], method='SLSQP',
+                       jac=self.jac, args=(-1.0,),
+                       constraints={'type': 'eq',
+                                    'fun': self.f_eqcon_scalar,
+                                    'args': (-1.0, ),
+                                    'jac': self.fprime_eqcon_scalar},
+                       options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_allclose(res.x, [1, 1])
+
+    def test_minimize_inequality_given(self):
+        # Minimize with method='SLSQP': inequality constraint, given Jacobian.
+        res = minimize(self.fun, [-1.0, 1.0], method='SLSQP',
+                       jac=self.jac, args=(-1.0, ),
+                       constraints={'type': 'ineq',
+                                    'fun': self.f_ieqcon,
+                                    'args': (-1.0, )},
+                       options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_allclose(res.x, [2, 1], atol=1e-3)
+
+    def test_minimize_inequality_given_vector_constraints(self):
+        # Minimize with method='SLSQP': vector inequality constraint, given
+        # Jacobian.
+        res = minimize(self.fun, [-1.0, 1.0], jac=self.jac,
+                       method='SLSQP', args=(-1.0,),
+                       constraints={'type': 'ineq',
+                                    'fun': self.f_ieqcon2,
+                                    'jac': self.fprime_ieqcon2},
+                       options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_allclose(res.x, [2, 1])
+
+    def test_minimize_bounded_constraint(self):
+        # when the constraint makes the solver go up against a parameter
+        # bound make sure that the numerical differentiation of the
+        # jacobian doesn't try to exceed that bound using a finite difference.
+        # gh11403
+        def c(x):
+            assert 0 <= x[0] <= 1 and 0 <= x[1] <= 1, x
+            return x[0] ** 0.5 + x[1]
+
+        def f(x):
+            assert 0 <= x[0] <= 1 and 0 <= x[1] <= 1, x
+            return -x[0] ** 2 + x[1] ** 2
+
+        cns = [NonlinearConstraint(c, 0, 1.5)]
+        x0 = np.asarray([0.9, 0.5])
+        bnd = Bounds([0., 0.], [1.0, 1.0])
+        minimize(f, x0, method='SLSQP', bounds=bnd, constraints=cns)
+
+    def test_minimize_bound_equality_given2(self):
+        # Minimize with method='SLSQP': bounds, eq. const., given jac. for
+        # fun. and const.
+        res = minimize(self.fun, [-1.0, 1.0], method='SLSQP',
+                       jac=self.jac, args=(-1.0, ),
+                       bounds=[(-0.8, 1.), (-1, 0.8)],
+                       constraints={'type': 'eq',
+                                    'fun': self.f_eqcon,
+                                    'args': (-1.0, ),
+                                    'jac': self.fprime_eqcon},
+                       options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_allclose(res.x, [0.8, 0.8], atol=1e-3)
+        assert_(-0.8 <= res.x[0] <= 1)
+        assert_(-1 <= res.x[1] <= 0.8)
+
+    # fmin_slsqp
+    def test_unbounded_approximated(self):
+        # SLSQP: unbounded, approximated Jacobian.
+        res = fmin_slsqp(self.fun, [-1.0, 1.0], args=(-1.0, ),
+                         iprint = 0, full_output = 1)
+        x, fx, its, imode, smode = res
+        assert_(imode == 0, imode)
+        assert_array_almost_equal(x, [2, 1])
+
+    def test_unbounded_given(self):
+        # SLSQP: unbounded, given Jacobian.
+        res = fmin_slsqp(self.fun, [-1.0, 1.0], args=(-1.0, ),
+                         fprime = self.jac, iprint = 0,
+                         full_output = 1)
+        x, fx, its, imode, smode = res
+        assert_(imode == 0, imode)
+        assert_array_almost_equal(x, [2, 1])
+
+    def test_equality_approximated(self):
+        # SLSQP: equality constraint, approximated Jacobian.
+        res = fmin_slsqp(self.fun,[-1.0,1.0], args=(-1.0,),
+                         eqcons = [self.f_eqcon],
+                         iprint = 0, full_output = 1)
+        x, fx, its, imode, smode = res
+        assert_(imode == 0, imode)
+        assert_array_almost_equal(x, [1, 1])
+
+    def test_equality_given(self):
+        # SLSQP: equality constraint, given Jacobian.
+        res = fmin_slsqp(self.fun, [-1.0, 1.0],
+                         fprime=self.jac, args=(-1.0,),
+                         eqcons = [self.f_eqcon], iprint = 0,
+                         full_output = 1)
+        x, fx, its, imode, smode = res
+        assert_(imode == 0, imode)
+        assert_array_almost_equal(x, [1, 1])
+
+    def test_equality_given2(self):
+        # SLSQP: equality constraint, given Jacobian for fun and const.
+        res = fmin_slsqp(self.fun, [-1.0, 1.0],
+                         fprime=self.jac, args=(-1.0,),
+                         f_eqcons = self.f_eqcon,
+                         fprime_eqcons = self.fprime_eqcon,
+                         iprint = 0,
+                         full_output = 1)
+        x, fx, its, imode, smode = res
+        assert_(imode == 0, imode)
+        assert_array_almost_equal(x, [1, 1])
+
+    def test_inequality_given(self):
+        # SLSQP: inequality constraint, given Jacobian.
+        res = fmin_slsqp(self.fun, [-1.0, 1.0],
+                         fprime=self.jac, args=(-1.0, ),
+                         ieqcons = [self.f_ieqcon],
+                         iprint = 0, full_output = 1)
+        x, fx, its, imode, smode = res
+        assert_(imode == 0, imode)
+        assert_array_almost_equal(x, [2, 1], decimal=3)
+
+    def test_bound_equality_given2(self):
+        # SLSQP: bounds, eq. const., given jac. for fun. and const.
+        res = fmin_slsqp(self.fun, [-1.0, 1.0],
+                         fprime=self.jac, args=(-1.0, ),
+                         bounds = [(-0.8, 1.), (-1, 0.8)],
+                         f_eqcons = self.f_eqcon,
+                         fprime_eqcons = self.fprime_eqcon,
+                         iprint = 0, full_output = 1)
+        x, fx, its, imode, smode = res
+        assert_(imode == 0, imode)
+        assert_array_almost_equal(x, [0.8, 0.8], decimal=3)
+        assert_(-0.8 <= x[0] <= 1)
+        assert_(-1 <= x[1] <= 0.8)
+
+    def test_scalar_constraints(self):
+        # Regression test for gh-2182
+        x = fmin_slsqp(lambda z: z**2, [3.],
+                       ieqcons=[lambda z: z[0] - 1],
+                       iprint=0)
+        assert_array_almost_equal(x, [1.])
+
+        x = fmin_slsqp(lambda z: z**2, [3.],
+                       f_ieqcons=lambda z: [z[0] - 1],
+                       iprint=0)
+        assert_array_almost_equal(x, [1.])
+
+    def test_integer_bounds(self):
+        # This should not raise an exception
+        fmin_slsqp(lambda z: z**2 - 1, [0], bounds=[[0, 1]], iprint=0)
+
+    def test_array_bounds(self):
+        # NumPy used to treat n-dimensional 1-element arrays as scalars
+        # in some cases.  The handling of `bounds` by `fmin_slsqp` still
+        # supports this behavior.
+        bounds = [(-np.inf, np.inf), (np.array([2]), np.array([3]))]
+        x = fmin_slsqp(lambda z: np.sum(z**2 - 1), [2.5, 2.5], bounds=bounds,
+                       iprint=0)
+        assert_array_almost_equal(x, [0, 2])
+
+    def test_obj_must_return_scalar(self):
+        # Regression test for Github Issue #5433
+        # If objective function does not return a scalar, raises ValueError
+        with assert_raises(ValueError):
+            fmin_slsqp(lambda x: [0, 1], [1, 2, 3])
+
+    def test_obj_returns_scalar_in_list(self):
+        # Test for Github Issue #5433 and PR #6691
+        # Objective function should be able to return length-1 Python list
+        #  containing the scalar
+        fmin_slsqp(lambda x: [0], [1, 2, 3], iprint=0)
+
+    def test_callback(self):
+        # Minimize, method='SLSQP': unbounded, approximated jacobian. Check for callback
+        callback = MyCallBack()
+        res = minimize(self.fun, [-1.0, 1.0], args=(-1.0, ),
+                       method='SLSQP', callback=callback, options=self.opts)
+        assert_(res['success'], res['message'])
+        assert_(callback.been_called)
+        assert_equal(callback.ncalls, res['nit'])
+
+    def test_inconsistent_linearization(self):
+        # SLSQP must be able to solve this problem, even if the
+        # linearized problem at the starting point is infeasible.
+
+        # Linearized constraints are
+        #
+        #    2*x0[0]*x[0] >= 1
+        #
+        # At x0 = [0, 1], the second constraint is clearly infeasible.
+        # This triggers a call with n2==1 in the LSQ subroutine.
+        x = [0, 1]
+        def f1(x):
+            return x[0] + x[1] - 2
+        def f2(x):
+            return x[0] ** 2 - 1
+        sol = minimize(
+            lambda x: x[0]**2 + x[1]**2,
+            x,
+            constraints=({'type':'eq','fun': f1},
+                         {'type':'ineq','fun': f2}),
+            bounds=((0,None), (0,None)),
+            method='SLSQP')
+        x = sol.x
+
+        assert_allclose(f1(x), 0, atol=1e-8)
+        assert_(f2(x) >= -1e-8)
+        assert_(sol.success, sol)
+
+    def test_regression_5743(self):
+        # SLSQP must not indicate success for this problem,
+        # which is infeasible.
+        x = [1, 2]
+        sol = minimize(
+            lambda x: x[0]**2 + x[1]**2,
+            x,
+            constraints=({'type':'eq','fun': lambda x: x[0]+x[1]-1},
+                         {'type':'ineq','fun': lambda x: x[0]-2}),
+            bounds=((0,None), (0,None)),
+            method='SLSQP')
+        assert_(not sol.success, sol)
+
+    def test_gh_6676(self):
+        def func(x):
+            return (x[0] - 1)**2 + 2*(x[1] - 1)**2 + 0.5*(x[2] - 1)**2
+
+        sol = minimize(func, [0, 0, 0], method='SLSQP')
+        assert_(sol.jac.shape == (3,))
+
+    def test_invalid_bounds(self):
+        # Raise correct error when lower bound is greater than upper bound.
+        # See Github issue 6875.
+        bounds_list = [
+            ((1, 2), (2, 1)),
+            ((2, 1), (1, 2)),
+            ((2, 1), (2, 1)),
+            ((np.inf, 0), (np.inf, 0)),
+            ((1, -np.inf), (0, 1)),
+        ]
+        for bounds in bounds_list:
+            with assert_raises(ValueError):
+                minimize(self.fun, [-1.0, 1.0], bounds=bounds, method='SLSQP')
+
+    def test_bounds_clipping(self):
+        #
+        # SLSQP returns bogus results for initial guess out of bounds, gh-6859
+        #
+        def f(x):
+            return (x[0] - 1)**2
+
+        sol = minimize(f, [10], method='slsqp', bounds=[(None, 0)])
+        assert_(sol.success)
+        assert_allclose(sol.x, 0, atol=1e-10)
+
+        sol = minimize(f, [-10], method='slsqp', bounds=[(2, None)])
+        assert_(sol.success)
+        assert_allclose(sol.x, 2, atol=1e-10)
+
+        sol = minimize(f, [-10], method='slsqp', bounds=[(None, 0)])
+        assert_(sol.success)
+        assert_allclose(sol.x, 0, atol=1e-10)
+
+        sol = minimize(f, [10], method='slsqp', bounds=[(2, None)])
+        assert_(sol.success)
+        assert_allclose(sol.x, 2, atol=1e-10)
+
+        sol = minimize(f, [-0.5], method='slsqp', bounds=[(-1, 0)])
+        assert_(sol.success)
+        assert_allclose(sol.x, 0, atol=1e-10)
+
+        sol = minimize(f, [10], method='slsqp', bounds=[(-1, 0)])
+        assert_(sol.success)
+        assert_allclose(sol.x, 0, atol=1e-10)
+
+    def test_infeasible_initial(self):
+        # Check SLSQP behavior with infeasible initial point
+        def f(x):
+            x, = x
+            return x*x - 2*x + 1
+
+        cons_u = [{'type': 'ineq', 'fun': lambda x: 0 - x}]
+        cons_l = [{'type': 'ineq', 'fun': lambda x: x - 2}]
+        cons_ul = [{'type': 'ineq', 'fun': lambda x: 0 - x},
+                   {'type': 'ineq', 'fun': lambda x: x + 1}]
+
+        sol = minimize(f, [10], method='slsqp', constraints=cons_u)
+        assert_(sol.success)
+        assert_allclose(sol.x, 0, atol=1e-10)
+
+        sol = minimize(f, [-10], method='slsqp', constraints=cons_l)
+        assert_(sol.success)
+        assert_allclose(sol.x, 2, atol=1e-10)
+
+        sol = minimize(f, [-10], method='slsqp', constraints=cons_u)
+        assert_(sol.success)
+        assert_allclose(sol.x, 0, atol=1e-10)
+
+        sol = minimize(f, [10], method='slsqp', constraints=cons_l)
+        assert_(sol.success)
+        assert_allclose(sol.x, 2, atol=1e-10)
+
+        sol = minimize(f, [-0.5], method='slsqp', constraints=cons_ul)
+        assert_(sol.success)
+        assert_allclose(sol.x, 0, atol=1e-10)
+
+        sol = minimize(f, [10], method='slsqp', constraints=cons_ul)
+        assert_(sol.success)
+        assert_allclose(sol.x, 0, atol=1e-10)
+
+    @pytest.mark.xfail(scipy.show_config(mode='dicts')['Compilers']['fortran']['name']
+                       == "intel-llvm",
+                       reason="Runtime warning due to floating point issues, not logic")
+    def test_inconsistent_inequalities(self):
+        # gh-7618
+
+        def cost(x):
+            return -1 * x[0] + 4 * x[1]
+
+        def ineqcons1(x):
+            return x[1] - x[0] - 1
+
+        def ineqcons2(x):
+            return x[0] - x[1]
+
+        # The inequalities are inconsistent, so no solution can exist:
+        #
+        # x1 >= x0 + 1
+        # x0 >= x1
+
+        x0 = (1,5)
+        bounds = ((-5, 5), (-5, 5))
+        cons = (dict(type='ineq', fun=ineqcons1), dict(type='ineq', fun=ineqcons2))
+        res = minimize(cost, x0, method='SLSQP', bounds=bounds, constraints=cons)
+
+        assert_(not res.success)
+
+    def test_new_bounds_type(self):
+        def f(x):
+            return x[0] ** 2 + x[1] ** 2
+        bounds = Bounds([1, 0], [np.inf, np.inf])
+        sol = minimize(f, [0, 0], method='slsqp', bounds=bounds)
+        assert_(sol.success)
+        assert_allclose(sol.x, [1, 0])
+
+    def test_nested_minimization(self):
+
+        class NestedProblem:
+
+            def __init__(self):
+                self.F_outer_count = 0
+
+            def F_outer(self, x):
+                self.F_outer_count += 1
+                if self.F_outer_count > 1000:
+                    raise Exception("Nested minimization failed to terminate.")
+                inner_res = minimize(self.F_inner, (3, 4), method="SLSQP")
+                assert_(inner_res.success)
+                assert_allclose(inner_res.x, [1, 1])
+                return x[0]**2 + x[1]**2 + x[2]**2
+
+            def F_inner(self, x):
+                return (x[0] - 1)**2 + (x[1] - 1)**2
+
+            def solve(self):
+                outer_res = minimize(self.F_outer, (5, 5, 5), method="SLSQP")
+                assert_(outer_res.success)
+                assert_allclose(outer_res.x, [0, 0, 0])
+
+        problem = NestedProblem()
+        problem.solve()
+
+    def test_gh1758(self):
+        # the test suggested in gh1758
+        # https://nlopt.readthedocs.io/en/latest/NLopt_Tutorial/
+        # implement two equality constraints, in R^2.
+        def fun(x):
+            return np.sqrt(x[1])
+
+        def f_eqcon(x):
+            """ Equality constraint """
+            return x[1] - (2 * x[0]) ** 3
+
+        def f_eqcon2(x):
+            """ Equality constraint """
+            return x[1] - (-x[0] + 1) ** 3
+
+        c1 = {'type': 'eq', 'fun': f_eqcon}
+        c2 = {'type': 'eq', 'fun': f_eqcon2}
+
+        res = minimize(fun, [8, 0.25], method='SLSQP',
+                       constraints=[c1, c2], bounds=[(-0.5, 1), (0, 8)])
+
+        np.testing.assert_allclose(res.fun, 0.5443310539518)
+        np.testing.assert_allclose(res.x, [0.33333333, 0.2962963])
+        assert res.success
+
+    def test_gh9640(self):
+        np.random.seed(10)
+        cons = ({'type': 'ineq', 'fun': lambda x: -x[0] - x[1] - 3},
+                {'type': 'ineq', 'fun': lambda x: x[1] + x[2] - 2})
+        bnds = ((-2, 2), (-2, 2), (-2, 2))
+
+        def target(x):
+            return 1
+        x0 = [-1.8869783504471584, -0.640096352696244, -0.8174212253407696]
+        res = minimize(target, x0, method='SLSQP', bounds=bnds, constraints=cons,
+                       options={'disp':False, 'maxiter':10000})
+
+        # The problem is infeasible, so it cannot succeed
+        assert not res.success
+
+    def test_parameters_stay_within_bounds(self):
+        # gh11403. For some problems the SLSQP Fortran code suggests a step
+        # outside one of the lower/upper bounds. When this happens
+        # approx_derivative complains because it's being asked to evaluate
+        # a gradient outside its domain.
+        np.random.seed(1)
+        bounds = Bounds(np.array([0.1]), np.array([1.0]))
+        n_inputs = len(bounds.lb)
+        x0 = np.array(bounds.lb + (bounds.ub - bounds.lb) *
+                      np.random.random(n_inputs))
+
+        def f(x):
+            assert (x >= bounds.lb).all()
+            return np.linalg.norm(x)
+        # The following should not raise any warnings which was the case, with the
+        # old Fortran code.
+        res = minimize(f, x0, method='SLSQP', bounds=bounds)
+        assert res.success
+
+
+def test_slsqp_segfault_wrong_workspace_computation():
+    # See gh-14915
+    # This problem is not well-defined, however should not cause a segfault.
+    # The previous F77 workspace computation did not handle only equality-
+    # constrained problems correctly.
+    rng = np.random.default_rng(1742651087222879)
+    x = rng.uniform(size=[22,365])
+    target = np.linspace(0.9, 4.0, 50)
+
+    def metric(v, weights):
+        return [[0, 0],[1, 1]]
+
+    def efficient_metric(v, target):
+        def metric_a(weights):
+            return metric(v, weights)[1][0]
+
+        def metric_b(weights, v):
+            return metric(v, weights)[0][0]
+
+        constraints = ({'type': 'eq', 'fun': lambda x: metric_a(x) - target},
+                       {'type': 'eq', 'fun': lambda x: np.sum(x) - 1})
+        weights = np.array([len(v)*[1./len(v)]])[0]
+        result = minimize(metric_b,
+                          weights,
+                          args=(v,),
+                          method='SLSQP',
+                          constraints=constraints)
+        return result
+
+    efficient_metric(x, target)
+

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_tnc.py

@@ -0,0 +1,345 @@
+"""
+Unit tests for TNC optimization routine from tnc.py
+"""
+import pytest
+from numpy.testing import assert_allclose, assert_equal
+
+import numpy as np
+from math import pow
+
+from scipy import optimize
+
+
+class TestTnc:
+    """TNC non-linear optimization.
+
+    These tests are taken from Prof. K. Schittkowski's test examples
+    for constrained non-linear programming.
+
+    http://www.uni-bayreuth.de/departments/math/~kschittkowski/home.htm
+
+    """
+    def setup_method(self):
+        # options for minimize
+        self.opts = {'disp': False, 'maxfun': 200}
+
+    # objective functions and Jacobian for each test
+    def f1(self, x, a=100.0):
+        return a * pow((x[1] - pow(x[0], 2)), 2) + pow(1.0 - x[0], 2)
+
+    def g1(self, x, a=100.0):
+        dif = [0, 0]
+        dif[1] = 2 * a * (x[1] - pow(x[0], 2))
+        dif[0] = -2.0 * (x[0] * (dif[1] - 1.0) + 1.0)
+        return dif
+
+    def fg1(self, x, a=100.0):
+        return self.f1(x, a), self.g1(x, a)
+
+    def f3(self, x):
+        return x[1] + pow(x[1] - x[0], 2) * 1.0e-5
+
+    def g3(self, x):
+        dif = [0, 0]
+        dif[0] = -2.0 * (x[1] - x[0]) * 1.0e-5
+        dif[1] = 1.0 - dif[0]
+        return dif
+
+    def fg3(self, x):
+        return self.f3(x), self.g3(x)
+
+    def f4(self, x):
+        return pow(x[0] + 1.0, 3) / 3.0 + x[1]
+
+    def g4(self, x):
+        dif = [0, 0]
+        dif[0] = pow(x[0] + 1.0, 2)
+        dif[1] = 1.0
+        return dif
+
+    def fg4(self, x):
+        return self.f4(x), self.g4(x)
+
+    def f5(self, x):
+        return np.sin(x[0] + x[1]) + pow(x[0] - x[1], 2) - \
+                1.5 * x[0] + 2.5 * x[1] + 1.0
+
+    def g5(self, x):
+        dif = [0, 0]
+        v1 = np.cos(x[0] + x[1])
+        v2 = 2.0*(x[0] - x[1])
+
+        dif[0] = v1 + v2 - 1.5
+        dif[1] = v1 - v2 + 2.5
+        return dif
+
+    def fg5(self, x):
+        return self.f5(x), self.g5(x)
+
+    def f38(self, x):
+        return (100.0 * pow(x[1] - pow(x[0], 2), 2) +
+                pow(1.0 - x[0], 2) + 90.0 * pow(x[3] - pow(x[2], 2), 2) +
+                pow(1.0 - x[2], 2) + 10.1 * (pow(x[1] - 1.0, 2) +
+                                             pow(x[3] - 1.0, 2)) +
+                19.8 * (x[1] - 1.0) * (x[3] - 1.0)) * 1.0e-5
+
+    def g38(self, x):
+        dif = [0, 0, 0, 0]
+        dif[0] = (-400.0 * x[0] * (x[1] - pow(x[0], 2)) -
+                  2.0 * (1.0 - x[0])) * 1.0e-5
+        dif[1] = (200.0 * (x[1] - pow(x[0], 2)) + 20.2 * (x[1] - 1.0) +
+                  19.8 * (x[3] - 1.0)) * 1.0e-5
+        dif[2] = (- 360.0 * x[2] * (x[3] - pow(x[2], 2)) -
+                  2.0 * (1.0 - x[2])) * 1.0e-5
+        dif[3] = (180.0 * (x[3] - pow(x[2], 2)) + 20.2 * (x[3] - 1.0) +
+                  19.8 * (x[1] - 1.0)) * 1.0e-5
+        return dif
+
+    def fg38(self, x):
+        return self.f38(x), self.g38(x)
+
+    def f45(self, x):
+        return 2.0 - x[0] * x[1] * x[2] * x[3] * x[4] / 120.0
+
+    def g45(self, x):
+        dif = [0] * 5
+        dif[0] = - x[1] * x[2] * x[3] * x[4] / 120.0
+        dif[1] = - x[0] * x[2] * x[3] * x[4] / 120.0
+        dif[2] = - x[0] * x[1] * x[3] * x[4] / 120.0
+        dif[3] = - x[0] * x[1] * x[2] * x[4] / 120.0
+        dif[4] = - x[0] * x[1] * x[2] * x[3] / 120.0
+        return dif
+
+    def fg45(self, x):
+        return self.f45(x), self.g45(x)
+
+    # tests
+    # minimize with method=TNC
+    def test_minimize_tnc1(self):
+        x0, bnds = [-2, 1], ([-np.inf, None], [-1.5, None])
+        xopt = [1, 1]
+        iterx = []  # to test callback
+
+        res = optimize.minimize(self.f1, x0, method='TNC', jac=self.g1,
+                                bounds=bnds, options=self.opts,
+                                callback=iterx.append)
+        assert_allclose(res.fun, self.f1(xopt), atol=1e-8)
+        assert_equal(len(iterx), res.nit)
+
+    def test_minimize_tnc1b(self):
+        x0, bnds = np.array([-2, 1]), ([-np.inf, None], [-1.5, None])
+        xopt = [1, 1]
+        x = optimize.minimize(self.f1, x0, method='TNC',
+                              bounds=bnds, options=self.opts).x
+        assert_allclose(self.f1(x), self.f1(xopt), atol=1e-4)
+
+    def test_minimize_tnc1c(self):
+        x0, bnds = [-2, 1], ([-np.inf, None],[-1.5, None])
+        xopt = [1, 1]
+        x = optimize.minimize(self.fg1, x0, method='TNC',
+                              jac=True, bounds=bnds,
+                              options=self.opts).x
+        assert_allclose(self.f1(x), self.f1(xopt), atol=1e-8)
+
+    def test_minimize_tnc2(self):
+        x0, bnds = [-2, 1], ([-np.inf, None], [1.5, None])
+        xopt = [-1.2210262419616387, 1.5]
+        x = optimize.minimize(self.f1, x0, method='TNC',
+                              jac=self.g1, bounds=bnds,
+                              options=self.opts).x
+        assert_allclose(self.f1(x), self.f1(xopt), atol=1e-8)
+
+    def test_minimize_tnc3(self):
+        x0, bnds = [10, 1], ([-np.inf, None], [0.0, None])
+        xopt = [0, 0]
+        x = optimize.minimize(self.f3, x0, method='TNC',
+                              jac=self.g3, bounds=bnds,
+                              options=self.opts).x
+        assert_allclose(self.f3(x), self.f3(xopt), atol=1e-8)
+
+    def test_minimize_tnc4(self):
+        x0,bnds = [1.125, 0.125], [(1, None), (0, None)]
+        xopt = [1, 0]
+        x = optimize.minimize(self.f4, x0, method='TNC',
+                              jac=self.g4, bounds=bnds,
+                              options=self.opts).x
+        assert_allclose(self.f4(x), self.f4(xopt), atol=1e-8)
+
+    def test_minimize_tnc5(self):
+        x0, bnds = [0, 0], [(-1.5, 4),(-3, 3)]
+        xopt = [-0.54719755119659763, -1.5471975511965976]
+        x = optimize.minimize(self.f5, x0, method='TNC',
+                              jac=self.g5, bounds=bnds,
+                              options=self.opts).x
+        assert_allclose(self.f5(x), self.f5(xopt), atol=1e-8)
+
+    def test_minimize_tnc38(self):
+        x0, bnds = np.array([-3, -1, -3, -1]), [(-10, 10)]*4
+        xopt = [1]*4
+        x = optimize.minimize(self.f38, x0, method='TNC',
+                              jac=self.g38, bounds=bnds,
+                              options=self.opts).x
+        assert_allclose(self.f38(x), self.f38(xopt), atol=1e-8)
+
+    def test_minimize_tnc45(self):
+        x0, bnds = [2] * 5, [(0, 1), (0, 2), (0, 3), (0, 4), (0, 5)]
+        xopt = [1, 2, 3, 4, 5]
+        x = optimize.minimize(self.f45, x0, method='TNC',
+                              jac=self.g45, bounds=bnds,
+                              options=self.opts).x
+        assert_allclose(self.f45(x), self.f45(xopt), atol=1e-8)
+
+    # fmin_tnc
+    def test_tnc1(self):
+        fg, x, bounds = self.fg1, [-2, 1], ([-np.inf, None], [-1.5, None])
+        xopt = [1, 1]
+
+        x, nf, rc = optimize.fmin_tnc(fg, x, bounds=bounds, args=(100.0, ),
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f1(x), self.f1(xopt), atol=1e-8,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_tnc1b(self):
+        x, bounds = [-2, 1], ([-np.inf, None], [-1.5, None])
+        xopt = [1, 1]
+
+        x, nf, rc = optimize.fmin_tnc(self.f1, x, approx_grad=True,
+                                      bounds=bounds,
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f1(x), self.f1(xopt), atol=1e-4,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_tnc1c(self):
+        x, bounds = [-2, 1], ([-np.inf, None], [-1.5, None])
+        xopt = [1, 1]
+
+        x, nf, rc = optimize.fmin_tnc(self.f1, x, fprime=self.g1,
+                                      bounds=bounds,
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f1(x), self.f1(xopt), atol=1e-8,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_tnc2(self):
+        fg, x, bounds = self.fg1, [-2, 1], ([-np.inf, None], [1.5, None])
+        xopt = [-1.2210262419616387, 1.5]
+
+        x, nf, rc = optimize.fmin_tnc(fg, x, bounds=bounds,
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f1(x), self.f1(xopt), atol=1e-8,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_tnc3(self):
+        fg, x, bounds = self.fg3, [10, 1], ([-np.inf, None], [0.0, None])
+        xopt = [0, 0]
+
+        x, nf, rc = optimize.fmin_tnc(fg, x, bounds=bounds,
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f3(x), self.f3(xopt), atol=1e-8,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_tnc4(self):
+        fg, x, bounds = self.fg4, [1.125, 0.125], [(1, None), (0, None)]
+        xopt = [1, 0]
+
+        x, nf, rc = optimize.fmin_tnc(fg, x, bounds=bounds,
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f4(x), self.f4(xopt), atol=1e-8,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_tnc5(self):
+        fg, x, bounds = self.fg5, [0, 0], [(-1.5, 4),(-3, 3)]
+        xopt = [-0.54719755119659763, -1.5471975511965976]
+
+        x, nf, rc = optimize.fmin_tnc(fg, x, bounds=bounds,
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f5(x), self.f5(xopt), atol=1e-8,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_tnc38(self):
+        fg, x, bounds = self.fg38, np.array([-3, -1, -3, -1]), [(-10, 10)]*4
+        xopt = [1]*4
+
+        x, nf, rc = optimize.fmin_tnc(fg, x, bounds=bounds,
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f38(x), self.f38(xopt), atol=1e-8,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_tnc45(self):
+        fg, x, bounds = self.fg45, [2] * 5, [(0, 1), (0, 2), (0, 3),
+                                             (0, 4), (0, 5)]
+        xopt = [1, 2, 3, 4, 5]
+
+        x, nf, rc = optimize.fmin_tnc(fg, x, bounds=bounds,
+                                      messages=optimize._tnc.MSG_NONE,
+                                      maxfun=200)
+
+        assert_allclose(self.f45(x), self.f45(xopt), atol=1e-8,
+                        err_msg="TNC failed with status: " +
+                                optimize._tnc.RCSTRINGS[rc])
+
+    def test_raising_exceptions(self):
+        # tnc was ported to cython from hand-crafted cpython code
+        # check that Exception handling works.
+        def myfunc(x):
+            raise RuntimeError("myfunc")
+
+        def myfunc1(x):
+            return optimize.rosen(x)
+
+        def callback(x):
+            raise ValueError("callback")
+
+        with pytest.raises(RuntimeError):
+            optimize.minimize(myfunc, [0, 1], method="TNC")
+
+        with pytest.raises(ValueError):
+            optimize.minimize(
+                myfunc1, [0, 1], method="TNC", callback=callback
+            )
+
+    def test_callback_shouldnt_affect_minimization(self):
+        # gh14879. The output of a TNC minimization was different depending
+        # on whether a callback was used or not. The two should be equivalent.
+        # The issue was that TNC was unscaling/scaling x, and this process was
+        # altering x in the process. Now the callback uses an unscaled
+        # temporary copy of x.
+        def callback(x):
+            pass
+
+        fun = optimize.rosen
+        bounds = [(0, 10)] * 4
+        x0 = [1, 2, 3, 4.]
+        res = optimize.minimize(
+            fun, x0, bounds=bounds, method="TNC", options={"maxfun": 1000}
+        )
+        res2 = optimize.minimize(
+            fun, x0, bounds=bounds, method="TNC", options={"maxfun": 1000},
+            callback=callback
+        )
+        assert_allclose(res2.x, res.x)
+        assert_allclose(res2.fun, res.fun)
+        assert_equal(res2.nfev, res.nfev)

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_trustregion.py

@@ -0,0 +1,110 @@
+"""
+Unit tests for trust-region optimization routines.
+
+"""
+import pytest
+import numpy as np
+from numpy.testing import assert_, assert_equal, assert_allclose
+from scipy.optimize import (minimize, rosen, rosen_der, rosen_hess,
+                            rosen_hess_prod)
+
+
+class Accumulator:
+    """ This is for testing callbacks."""
+    def __init__(self):
+        self.count = 0
+        self.accum = None
+
+    def __call__(self, x):
+        self.count += 1
+        if self.accum is None:
+            self.accum = np.array(x)
+        else:
+            self.accum += x
+
+
+class TestTrustRegionSolvers:
+
+    def setup_method(self):
+        self.x_opt = [1.0, 1.0]
+        self.easy_guess = [2.0, 2.0]
+        self.hard_guess = [-1.2, 1.0]
+
+    def test_dogleg_accuracy(self):
+        # test the accuracy and the return_all option
+        x0 = self.hard_guess
+        r = minimize(rosen, x0, jac=rosen_der, hess=rosen_hess, tol=1e-8,
+                     method='dogleg', options={'return_all': True},)
+        assert_allclose(x0, r['allvecs'][0])
+        assert_allclose(r['x'], r['allvecs'][-1])
+        assert_allclose(r['x'], self.x_opt)
+
+    def test_dogleg_callback(self):
+        # test the callback mechanism and the maxiter and return_all options
+        accumulator = Accumulator()
+        maxiter = 5
+        r = minimize(rosen, self.hard_guess, jac=rosen_der, hess=rosen_hess,
+                     callback=accumulator, method='dogleg',
+                     options={'return_all': True, 'maxiter': maxiter},)
+        assert_equal(accumulator.count, maxiter)
+        assert_equal(len(r['allvecs']), maxiter+1)
+        assert_allclose(r['x'], r['allvecs'][-1])
+        assert_allclose(sum(r['allvecs'][1:]), accumulator.accum)
+
+    @pytest.mark.thread_unsafe
+    def test_dogleg_user_warning(self):
+        with pytest.warns(RuntimeWarning,
+                          match=r'Maximum number of iterations'):
+            minimize(rosen, self.hard_guess, jac=rosen_der,
+                     hess=rosen_hess, method='dogleg',
+                     options={'disp': True, 'maxiter': 1}, )
+
+    def test_solver_concordance(self):
+        # Assert that dogleg uses fewer iterations than ncg on the Rosenbrock
+        # test function, although this does not necessarily mean
+        # that dogleg is faster or better than ncg even for this function
+        # and especially not for other test functions.
+        f = rosen
+        g = rosen_der
+        h = rosen_hess
+        for x0 in (self.easy_guess, self.hard_guess):
+            r_dogleg = minimize(f, x0, jac=g, hess=h, tol=1e-8,
+                                method='dogleg', options={'return_all': True})
+            r_trust_ncg = minimize(f, x0, jac=g, hess=h, tol=1e-8,
+                                   method='trust-ncg',
+                                   options={'return_all': True})
+            r_trust_krylov = minimize(f, x0, jac=g, hess=h, tol=1e-8,
+                                   method='trust-krylov',
+                                   options={'return_all': True})
+            r_ncg = minimize(f, x0, jac=g, hess=h, tol=1e-8,
+                             method='newton-cg', options={'return_all': True})
+            r_iterative = minimize(f, x0, jac=g, hess=h, tol=1e-8,
+                                   method='trust-exact',
+                                   options={'return_all': True})
+            assert_allclose(self.x_opt, r_dogleg['x'])
+            assert_allclose(self.x_opt, r_trust_ncg['x'])
+            assert_allclose(self.x_opt, r_trust_krylov['x'])
+            assert_allclose(self.x_opt, r_ncg['x'])
+            assert_allclose(self.x_opt, r_iterative['x'])
+            assert_(len(r_dogleg['allvecs']) < len(r_ncg['allvecs']))
+
+    def test_trust_ncg_hessp(self):
+        for x0 in (self.easy_guess, self.hard_guess, self.x_opt):
+            r = minimize(rosen, x0, jac=rosen_der, hessp=rosen_hess_prod,
+                         tol=1e-8, method='trust-ncg')
+            assert_allclose(self.x_opt, r['x'])
+
+    def test_trust_ncg_start_in_optimum(self):
+        r = minimize(rosen, x0=self.x_opt, jac=rosen_der, hess=rosen_hess,
+                     tol=1e-8, method='trust-ncg')
+        assert_allclose(self.x_opt, r['x'])
+
+    def test_trust_krylov_start_in_optimum(self):
+        r = minimize(rosen, x0=self.x_opt, jac=rosen_der, hess=rosen_hess,
+                     tol=1e-8, method='trust-krylov')
+        assert_allclose(self.x_opt, r['x'])
+
+    def test_trust_exact_start_in_optimum(self):
+        r = minimize(rosen, x0=self.x_opt, jac=rosen_der, hess=rosen_hess,
+                     tol=1e-8, method='trust-exact')
+        assert_allclose(self.x_opt, r['x'])

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_trustregion_exact.py

@@ -0,0 +1,351 @@
+"""
+Unit tests for trust-region iterative subproblem.
+
+"""
+import pytest
+import numpy as np
+from scipy.optimize._trustregion_exact import (
+    estimate_smallest_singular_value,
+    singular_leading_submatrix,
+    IterativeSubproblem)
+from scipy.linalg import (svd, get_lapack_funcs, det, qr, norm)
+from numpy.testing import (assert_array_equal,
+                           assert_equal, assert_array_almost_equal)
+
+
+def random_entry(n, min_eig, max_eig, case):
+
+    # Generate random matrix
+    rand = np.random.uniform(-1, 1, (n, n))
+
+    # QR decomposition
+    Q, _, _ = qr(rand, pivoting='True')
+
+    # Generate random eigenvalues
+    eigvalues = np.random.uniform(min_eig, max_eig, n)
+    eigvalues = np.sort(eigvalues)[::-1]
+
+    # Generate matrix
+    Qaux = np.multiply(eigvalues, Q)
+    A = np.dot(Qaux, Q.T)
+
+    # Generate gradient vector accordingly
+    # to the case is being tested.
+    if case == 'hard':
+        g = np.zeros(n)
+        g[:-1] = np.random.uniform(-1, 1, n-1)
+        g = np.dot(Q, g)
+    elif case == 'jac_equal_zero':
+        g = np.zeros(n)
+    else:
+        g = np.random.uniform(-1, 1, n)
+
+    return A, g
+
+
+class TestEstimateSmallestSingularValue:
+
+    def test_for_ill_condiotioned_matrix(self):
+
+        # Ill-conditioned triangular matrix
+        C = np.array([[1, 2, 3, 4],
+                      [0, 0.05, 60, 7],
+                      [0, 0, 0.8, 9],
+                      [0, 0, 0, 10]])
+
+        # Get svd decomposition
+        U, s, Vt = svd(C)
+
+        # Get smallest singular value and correspondent right singular vector.
+        smin_svd = s[-1]
+        zmin_svd = Vt[-1, :]
+
+        # Estimate smallest singular value
+        smin, zmin = estimate_smallest_singular_value(C)
+
+        # Check the estimation
+        assert_array_almost_equal(smin, smin_svd, decimal=8)
+        assert_array_almost_equal(abs(zmin), abs(zmin_svd), decimal=8)
+
+
+class TestSingularLeadingSubmatrix:
+
+    def test_for_already_singular_leading_submatrix(self):
+
+        # Define test matrix A.
+        # Note that the leading 2x2 submatrix is singular.
+        A = np.array([[1, 2, 3],
+                      [2, 4, 5],
+                      [3, 5, 6]])
+
+        # Get Cholesky from lapack functions
+        cholesky, = get_lapack_funcs(('potrf',), (A,))
+
+        # Compute Cholesky Decomposition
+        c, k = cholesky(A, lower=False, overwrite_a=False, clean=True)
+
+        delta, v = singular_leading_submatrix(A, c, k)
+
+        A[k-1, k-1] += delta
+
+        # Check if the leading submatrix is singular.
+        assert_array_almost_equal(det(A[:k, :k]), 0)
+
+        # Check if `v` fulfil the specified properties
+        quadratic_term = np.dot(v, np.dot(A, v))
+        assert_array_almost_equal(quadratic_term, 0)
+
+    def test_for_simetric_indefinite_matrix(self):
+
+        # Define test matrix A.
+        # Note that the leading 5x5 submatrix is indefinite.
+        A = np.asarray([[1, 2, 3, 7, 8],
+                        [2, 5, 5, 9, 0],
+                        [3, 5, 11, 1, 2],
+                        [7, 9, 1, 7, 5],
+                        [8, 0, 2, 5, 8]])
+
+        # Get Cholesky from lapack functions
+        cholesky, = get_lapack_funcs(('potrf',), (A,))
+
+        # Compute Cholesky Decomposition
+        c, k = cholesky(A, lower=False, overwrite_a=False, clean=True)
+
+        delta, v = singular_leading_submatrix(A, c, k)
+
+        A[k-1, k-1] += delta
+
+        # Check if the leading submatrix is singular.
+        assert_array_almost_equal(det(A[:k, :k]), 0)
+
+        # Check if `v` fulfil the specified properties
+        quadratic_term = np.dot(v, np.dot(A, v))
+        assert_array_almost_equal(quadratic_term, 0)
+
+    def test_for_first_element_equal_to_zero(self):
+
+        # Define test matrix A.
+        # Note that the leading 2x2 submatrix is singular.
+        A = np.array([[0, 3, 11],
+                      [3, 12, 5],
+                      [11, 5, 6]])
+
+        # Get Cholesky from lapack functions
+        cholesky, = get_lapack_funcs(('potrf',), (A,))
+
+        # Compute Cholesky Decomposition
+        c, k = cholesky(A, lower=False, overwrite_a=False, clean=True)
+
+        delta, v = singular_leading_submatrix(A, c, k)
+
+        A[k-1, k-1] += delta
+
+        # Check if the leading submatrix is singular
+        assert_array_almost_equal(det(A[:k, :k]), 0)
+
+        # Check if `v` fulfil the specified properties
+        quadratic_term = np.dot(v, np.dot(A, v))
+        assert_array_almost_equal(quadratic_term, 0)
+
+
+class TestIterativeSubproblem:
+
+    def test_for_the_easy_case(self):
+
+        # `H` is chosen such that `g` is not orthogonal to the
+        # eigenvector associated with the smallest eigenvalue `s`.
+        H = [[10, 2, 3, 4],
+             [2, 1, 7, 1],
+             [3, 7, 1, 7],
+             [4, 1, 7, 2]]
+        g = [1, 1, 1, 1]
+
+        # Trust Radius
+        trust_radius = 1
+
+        # Solve Subproblem
+        subprob = IterativeSubproblem(x=0,
+                                      fun=lambda x: 0,
+                                      jac=lambda x: np.array(g),
+                                      hess=lambda x: np.array(H),
+                                      k_easy=1e-10,
+                                      k_hard=1e-10)
+        p, hits_boundary = subprob.solve(trust_radius)
+
+        assert_array_almost_equal(p, [0.00393332, -0.55260862,
+                                      0.67065477, -0.49480341])
+        assert_array_almost_equal(hits_boundary, True)
+
+    def test_for_the_hard_case(self):
+
+        # `H` is chosen such that `g` is orthogonal to the
+        # eigenvector associated with the smallest eigenvalue `s`.
+        H = [[10, 2, 3, 4],
+             [2, 1, 7, 1],
+             [3, 7, 1, 7],
+             [4, 1, 7, 2]]
+        g = [6.4852641521327437, 1, 1, 1]
+        s = -8.2151519874416614
+
+        # Trust Radius
+        trust_radius = 1
+
+        # Solve Subproblem
+        subprob = IterativeSubproblem(x=0,
+                                      fun=lambda x: 0,
+                                      jac=lambda x: np.array(g),
+                                      hess=lambda x: np.array(H),
+                                      k_easy=1e-10,
+                                      k_hard=1e-10)
+        p, hits_boundary = subprob.solve(trust_radius)
+
+        assert_array_almost_equal(-s, subprob.lambda_current)
+
+    def test_for_interior_convergence(self):
+
+        H = [[1.812159, 0.82687265, 0.21838879, -0.52487006, 0.25436988],
+             [0.82687265, 2.66380283, 0.31508988, -0.40144163, 0.08811588],
+             [0.21838879, 0.31508988, 2.38020726, -0.3166346, 0.27363867],
+             [-0.52487006, -0.40144163, -0.3166346, 1.61927182, -0.42140166],
+             [0.25436988, 0.08811588, 0.27363867, -0.42140166, 1.33243101]]
+
+        g = [0.75798952, 0.01421945, 0.33847612, 0.83725004, -0.47909534]
+
+        # Solve Subproblem
+        subprob = IterativeSubproblem(x=0,
+                                      fun=lambda x: 0,
+                                      jac=lambda x: np.array(g),
+                                      hess=lambda x: np.array(H))
+        p, hits_boundary = subprob.solve(1.1)
+
+        assert_array_almost_equal(p, [-0.68585435, 0.1222621, -0.22090999,
+                                      -0.67005053, 0.31586769])
+        assert_array_almost_equal(hits_boundary, False)
+        assert_array_almost_equal(subprob.lambda_current, 0)
+        assert_array_almost_equal(subprob.niter, 1)
+
+    def test_for_jac_equal_zero(self):
+
+        H = [[0.88547534, 2.90692271, 0.98440885, -0.78911503, -0.28035809],
+             [2.90692271, -0.04618819, 0.32867263, -0.83737945, 0.17116396],
+             [0.98440885, 0.32867263, -0.87355957, -0.06521957, -1.43030957],
+             [-0.78911503, -0.83737945, -0.06521957, -1.645709, -0.33887298],
+             [-0.28035809, 0.17116396, -1.43030957, -0.33887298, -1.68586978]]
+
+        g = [0, 0, 0, 0, 0]
+
+        # Solve Subproblem
+        subprob = IterativeSubproblem(x=0,
+                                      fun=lambda x: 0,
+                                      jac=lambda x: np.array(g),
+                                      hess=lambda x: np.array(H),
+                                      k_easy=1e-10,
+                                      k_hard=1e-10)
+        p, hits_boundary = subprob.solve(1.1)
+
+        assert_array_almost_equal(p, [0.06910534, -0.01432721,
+                                      -0.65311947, -0.23815972,
+                                      -0.84954934])
+        assert_array_almost_equal(hits_boundary, True)
+
+    def test_for_jac_very_close_to_zero(self):
+
+        H = [[0.88547534, 2.90692271, 0.98440885, -0.78911503, -0.28035809],
+             [2.90692271, -0.04618819, 0.32867263, -0.83737945, 0.17116396],
+             [0.98440885, 0.32867263, -0.87355957, -0.06521957, -1.43030957],
+             [-0.78911503, -0.83737945, -0.06521957, -1.645709, -0.33887298],
+             [-0.28035809, 0.17116396, -1.43030957, -0.33887298, -1.68586978]]
+
+        g = [0, 0, 0, 0, 1e-15]
+
+        # Solve Subproblem
+        subprob = IterativeSubproblem(x=0,
+                                      fun=lambda x: 0,
+                                      jac=lambda x: np.array(g),
+                                      hess=lambda x: np.array(H),
+                                      k_easy=1e-10,
+                                      k_hard=1e-10)
+        p, hits_boundary = subprob.solve(1.1)
+
+        assert_array_almost_equal(p, [0.06910534, -0.01432721,
+                                      -0.65311947, -0.23815972,
+                                      -0.84954934])
+        assert_array_almost_equal(hits_boundary, True)
+
+    @pytest.mark.fail_slow(10)
+    def test_for_random_entries(self):
+        # Seed
+        np.random.seed(1)
+
+        # Dimension
+        n = 5
+
+        for case in ('easy', 'hard', 'jac_equal_zero'):
+
+            eig_limits = [(-20, -15),
+                          (-10, -5),
+                          (-10, 0),
+                          (-5, 5),
+                          (-10, 10),
+                          (0, 10),
+                          (5, 10),
+                          (15, 20)]
+
+            for min_eig, max_eig in eig_limits:
+                # Generate random symmetric matrix H with
+                # eigenvalues between min_eig and max_eig.
+                H, g = random_entry(n, min_eig, max_eig, case)
+
+                # Trust radius
+                trust_radius_list = [0.1, 0.3, 0.6, 0.8, 1, 1.2, 3.3, 5.5, 10]
+
+                for trust_radius in trust_radius_list:
+                    # Solve subproblem with very high accuracy
+                    subprob_ac = IterativeSubproblem(0,
+                                                     lambda x: 0,
+                                                     lambda x: g,
+                                                     lambda x: H,
+                                                     k_easy=1e-10,
+                                                     k_hard=1e-10)
+
+                    p_ac, hits_boundary_ac = subprob_ac.solve(trust_radius)
+
+                    # Compute objective function value
+                    J_ac = 1/2*np.dot(p_ac, np.dot(H, p_ac))+np.dot(g, p_ac)
+
+                    stop_criteria = [(0.1, 2),
+                                     (0.5, 1.1),
+                                     (0.9, 1.01)]
+
+                    for k_opt, k_trf in stop_criteria:
+
+                        # k_easy and k_hard computed in function
+                        # of k_opt and k_trf accordingly to
+                        # Conn, A. R., Gould, N. I., & Toint, P. L. (2000).
+                        # "Trust region methods". Siam. p. 197.
+                        k_easy = min(k_trf-1,
+                                     1-np.sqrt(k_opt))
+                        k_hard = 1-k_opt
+
+                        # Solve subproblem
+                        subprob = IterativeSubproblem(0,
+                                                      lambda x: 0,
+                                                      lambda x: g,
+                                                      lambda x: H,
+                                                      k_easy=k_easy,
+                                                      k_hard=k_hard)
+                        p, hits_boundary = subprob.solve(trust_radius)
+
+                        # Compute objective function value
+                        J = 1/2*np.dot(p, np.dot(H, p))+np.dot(g, p)
+
+                        # Check if it respect k_trf
+                        if hits_boundary:
+                            assert_array_equal(np.abs(norm(p)-trust_radius) <=
+                                               (k_trf-1)*trust_radius, True)
+                        else:
+                            assert_equal(norm(p) <= trust_radius, True)
+
+                        # Check if it respect k_opt
+                        assert_equal(J <= k_opt*J_ac, True)
+

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_trustregion_krylov.py

@@ -0,0 +1,170 @@
+"""
+Unit tests for Krylov space trust-region subproblem solver.
+
+"""
+import pytest
+import numpy as np
+from scipy.optimize._trlib import (get_trlib_quadratic_subproblem)
+from numpy.testing import (assert_,
+                           assert_almost_equal,
+                           assert_equal, assert_array_almost_equal)
+
+KrylovQP = get_trlib_quadratic_subproblem(tol_rel_i=1e-8, tol_rel_b=1e-6)
+KrylovQP_disp = get_trlib_quadratic_subproblem(tol_rel_i=1e-8, tol_rel_b=1e-6,
+                                               disp=True)
+
+class TestKrylovQuadraticSubproblem:
+
+    def test_for_the_easy_case(self):
+
+        # `H` is chosen such that `g` is not orthogonal to the
+        # eigenvector associated with the smallest eigenvalue.
+        H = np.array([[1.0, 0.0, 4.0],
+                      [0.0, 2.0, 0.0],
+                      [4.0, 0.0, 3.0]])
+        g = np.array([5.0, 0.0, 4.0])
+
+        # Trust Radius
+        trust_radius = 1.0
+
+        # Solve Subproblem
+        subprob = KrylovQP(x=0,
+                           fun=lambda x: 0,
+                           jac=lambda x: g,
+                           hess=lambda x: None,
+                           hessp=lambda x, y: H.dot(y))
+        p, hits_boundary = subprob.solve(trust_radius)
+
+        assert_array_almost_equal(p, np.array([-1.0, 0.0, 0.0]))
+        assert_equal(hits_boundary, True)
+        # check kkt satisfaction
+        assert_almost_equal(
+                np.linalg.norm(H.dot(p) + subprob.lam * p + g),
+                0.0)
+        # check trust region constraint
+        assert_almost_equal(np.linalg.norm(p), trust_radius)
+
+        trust_radius = 0.5
+        p, hits_boundary = subprob.solve(trust_radius)
+
+        assert_array_almost_equal(p,
+                np.array([-0.46125446, 0., -0.19298788]))
+        assert_equal(hits_boundary, True)
+        # check kkt satisfaction
+        assert_almost_equal(
+                np.linalg.norm(H.dot(p) + subprob.lam * p + g),
+                0.0)
+        # check trust region constraint
+        assert_almost_equal(np.linalg.norm(p), trust_radius)
+
+    def test_for_the_hard_case(self):
+
+        # `H` is chosen such that `g` is orthogonal to the
+        # eigenvector associated with the smallest eigenvalue.
+        H = np.array([[1.0, 0.0, 4.0],
+                      [0.0, 2.0, 0.0],
+                      [4.0, 0.0, 3.0]])
+        g = np.array([0.0, 2.0, 0.0])
+
+        # Trust Radius
+        trust_radius = 1.0
+
+        # Solve Subproblem
+        subprob = KrylovQP(x=0,
+                           fun=lambda x: 0,
+                           jac=lambda x: g,
+                           hess=lambda x: None,
+                           hessp=lambda x, y: H.dot(y))
+        p, hits_boundary = subprob.solve(trust_radius)
+
+        assert_array_almost_equal(p, np.array([0.0, -1.0, 0.0]))
+        # check kkt satisfaction
+        assert_almost_equal(
+                np.linalg.norm(H.dot(p) + subprob.lam * p + g),
+                0.0)
+        # check trust region constraint
+        assert_almost_equal(np.linalg.norm(p), trust_radius)
+
+        trust_radius = 0.5
+        p, hits_boundary = subprob.solve(trust_radius)
+
+        assert_array_almost_equal(p, np.array([0.0, -0.5, 0.0]))
+        # check kkt satisfaction
+        assert_almost_equal(
+                np.linalg.norm(H.dot(p) + subprob.lam * p + g),
+                0.0)
+        # check trust region constraint
+        assert_almost_equal(np.linalg.norm(p), trust_radius)
+
+    def test_for_interior_convergence(self):
+
+        H = np.array([[1.812159, 0.82687265, 0.21838879, -0.52487006, 0.25436988],
+                      [0.82687265, 2.66380283, 0.31508988, -0.40144163, 0.08811588],
+                      [0.21838879, 0.31508988, 2.38020726, -0.3166346, 0.27363867],
+                      [-0.52487006, -0.40144163, -0.3166346, 1.61927182, -0.42140166],
+                      [0.25436988, 0.08811588, 0.27363867, -0.42140166, 1.33243101]])
+        g = np.array([0.75798952, 0.01421945, 0.33847612, 0.83725004, -0.47909534])
+        trust_radius = 1.1
+
+        # Solve Subproblem
+        subprob = KrylovQP(x=0,
+                           fun=lambda x: 0,
+                           jac=lambda x: g,
+                           hess=lambda x: None,
+                           hessp=lambda x, y: H.dot(y))
+        p, hits_boundary = subprob.solve(trust_radius)
+
+        # check kkt satisfaction
+        assert_almost_equal(
+                np.linalg.norm(H.dot(p) + subprob.lam * p + g),
+                0.0)
+
+        assert_array_almost_equal(p, [-0.68585435, 0.1222621, -0.22090999,
+                                      -0.67005053, 0.31586769])
+        assert_array_almost_equal(hits_boundary, False)
+
+    def test_for_very_close_to_zero(self):
+
+        H = np.array([[0.88547534, 2.90692271, 0.98440885, -0.78911503, -0.28035809],
+                      [2.90692271, -0.04618819, 0.32867263, -0.83737945, 0.17116396],
+                      [0.98440885, 0.32867263, -0.87355957, -0.06521957, -1.43030957],
+                      [-0.78911503, -0.83737945, -0.06521957, -1.645709, -0.33887298],
+                      [-0.28035809, 0.17116396, -1.43030957, -0.33887298, -1.68586978]])
+        g = np.array([0, 0, 0, 0, 1e-6])
+        trust_radius = 1.1
+
+        # Solve Subproblem
+        subprob = KrylovQP(x=0,
+                           fun=lambda x: 0,
+                           jac=lambda x: g,
+                           hess=lambda x: None,
+                           hessp=lambda x, y: H.dot(y))
+        p, hits_boundary = subprob.solve(trust_radius)
+
+        # check kkt satisfaction
+        assert_almost_equal(
+                np.linalg.norm(H.dot(p) + subprob.lam * p + g),
+                0.0)
+        # check trust region constraint
+        assert_almost_equal(np.linalg.norm(p), trust_radius)
+
+        assert_array_almost_equal(p, [0.06910534, -0.01432721,
+                                      -0.65311947, -0.23815972,
+                                      -0.84954934])
+        assert_array_almost_equal(hits_boundary, True)
+
+    @pytest.mark.thread_unsafe
+    def test_disp(self, capsys):
+        H = -np.eye(5)
+        g = np.array([0, 0, 0, 0, 1e-6])
+        trust_radius = 1.1
+
+        subprob = KrylovQP_disp(x=0,
+                                fun=lambda x: 0,
+                                jac=lambda x: g,
+                                hess=lambda x: None,
+                                hessp=lambda x, y: H.dot(y))
+        p, hits_boundary = subprob.solve(trust_radius)
+        out, err = capsys.readouterr()
+        assert_(out.startswith(' TR Solving trust region problem'), repr(out))
+

venv/lib/python3.13/site-packages/scipy/optimize/tests/test_zeros.py

@@ -0,0 +1,998 @@
+import pytest
+
+from functools import lru_cache
+
+from numpy.testing import (assert_warns, assert_,
+                           assert_allclose,
+                           assert_equal,
+                           assert_array_equal,
+                           suppress_warnings)
+import numpy as np
+from numpy import finfo, power, nan, isclose, sqrt, exp, sin, cos
+
+from scipy import optimize
+from scipy.optimize import (_zeros_py as zeros, newton, root_scalar,
+                            OptimizeResult)
+
+from scipy._lib._util import getfullargspec_no_self as _getfullargspec
+
+# Import testing parameters
+from scipy.optimize._tstutils import get_tests, functions as tstutils_functions
+
+TOL = 4*np.finfo(float).eps  # tolerance
+
+_FLOAT_EPS = finfo(float).eps
+
+bracket_methods = [zeros.bisect, zeros.ridder, zeros.brentq, zeros.brenth,
+                   zeros.toms748]
+gradient_methods = [zeros.newton]
+all_methods = bracket_methods + gradient_methods
+
+# A few test functions used frequently:
+# # A simple quadratic, (x-1)^2 - 1
+def f1(x):
+    return x ** 2 - 2 * x - 1
+
+
+def f1_1(x):
+    return 2 * x - 2
+
+
+def f1_2(x):
+    return 2.0 + 0 * x
+
+
+def f1_and_p_and_pp(x):
+    return f1(x), f1_1(x), f1_2(x)
+
+
+# Simple transcendental function
+def f2(x):
+    return exp(x) - cos(x)
+
+
+def f2_1(x):
+    return exp(x) + sin(x)
+
+
+def f2_2(x):
+    return exp(x) + cos(x)
+
+
+# lru cached function
+@lru_cache
+def f_lrucached(x):
+    return x
+
+
+class TestScalarRootFinders:
+    # Basic tests for all scalar root finders
+
+    xtol = 4 * np.finfo(float).eps
+    rtol = 4 * np.finfo(float).eps
+
+    def _run_one_test(self, tc, method, sig_args_keys=None,
+                      sig_kwargs_keys=None, **kwargs):
+        method_args = []
+        for k in sig_args_keys or []:
+            if k not in tc:
+                # If a,b not present use x0, x1. Similarly for f and func
+                k = {'a': 'x0', 'b': 'x1', 'func': 'f'}.get(k, k)
+            method_args.append(tc[k])
+
+        method_kwargs = dict(**kwargs)
+        method_kwargs.update({'full_output': True, 'disp': False})
+        for k in sig_kwargs_keys or []:
+            method_kwargs[k] = tc[k]
+
+        root = tc.get('root')
+        func_args = tc.get('args', ())
+
+        try:
+            r, rr = method(*method_args, args=func_args, **method_kwargs)
+            return root, rr, tc
+        except Exception:
+            return root, zeros.RootResults(nan, -1, -1, zeros._EVALUEERR, method), tc
+
+    def run_tests(self, tests, method, name, known_fail=None, **kwargs):
+        r"""Run test-cases using the specified method and the supplied signature.
+
+        Extract the arguments for the method call from the test case
+        dictionary using the supplied keys for the method's signature."""
+        # The methods have one of two base signatures:
+        # (f, a, b, **kwargs)  # newton
+        # (func, x0, **kwargs)  # bisect/brentq/...
+
+        # FullArgSpec with args, varargs, varkw, defaults, ...
+        sig = _getfullargspec(method)
+        assert_(not sig.kwonlyargs)
+        nDefaults = len(sig.defaults)
+        nRequired = len(sig.args) - nDefaults
+        sig_args_keys = sig.args[:nRequired]
+        sig_kwargs_keys = []
+        if name in ['secant', 'newton', 'halley']:
+            if name in ['newton', 'halley']:
+                sig_kwargs_keys.append('fprime')
+                if name in ['halley']:
+                    sig_kwargs_keys.append('fprime2')
+            kwargs['tol'] = self.xtol
+        else:
+            kwargs['xtol'] = self.xtol
+            kwargs['rtol'] = self.rtol
+
+        results = [list(self._run_one_test(
+            tc, method, sig_args_keys=sig_args_keys,
+            sig_kwargs_keys=sig_kwargs_keys, **kwargs)) for tc in tests]
+        # results= [[true root, full output, tc], ...]
+
+        known_fail = known_fail or []
+        notcvgd = [elt for elt in results if not elt[1].converged]
+        notcvgd = [elt for elt in notcvgd if elt[-1]['ID'] not in known_fail]
+        notcvged_IDS = [elt[-1]['ID'] for elt in notcvgd]
+        assert_equal([len(notcvged_IDS), notcvged_IDS], [0, []])
+
+        # The usable xtol and rtol depend on the test
+        tols = {'xtol': self.xtol, 'rtol': self.rtol}
+        tols.update(**kwargs)
+        rtol = tols['rtol']
+        atol = tols.get('tol', tols['xtol'])
+
+        cvgd = [elt for elt in results if elt[1].converged]
+        approx = [elt[1].root for elt in cvgd]
+        correct = [elt[0] for elt in cvgd]
+        # See if the root matches the reference value
+        notclose = [[a] + elt for a, c, elt in zip(approx, correct, cvgd) if
+                    not isclose(a, c, rtol=rtol, atol=atol)
+                    and elt[-1]['ID'] not in known_fail]
+        # If not, evaluate the function and see if is 0 at the purported root
+        fvs = [tc['f'](aroot, *tc.get('args', tuple()))
+               for aroot, c, fullout, tc in notclose]
+        notclose = [[fv] + elt for fv, elt in zip(fvs, notclose) if fv != 0]
+        assert_equal([notclose, len(notclose)], [[], 0])
+        method_from_result = [result[1].method for result in results]
+        expected_method = [name for _ in results]
+        assert_equal(method_from_result, expected_method)
+
+    def run_collection(self, collection, method, name, smoothness=None,
+                       known_fail=None, **kwargs):
+        r"""Run a collection of tests using the specified method.
+
+        The name is used to determine some optional arguments."""
+        tests = get_tests(collection, smoothness=smoothness)
+        self.run_tests(tests, method, name, known_fail=known_fail, **kwargs)
+
+
+class TestBracketMethods(TestScalarRootFinders):
+    @pytest.mark.parametrize('method', bracket_methods)
+    @pytest.mark.parametrize('function', tstutils_functions)
+    def test_basic_root_scalar(self, method, function):
+        # Tests bracketing root finders called via `root_scalar` on a small
+        # set of simple problems, each of which has a root at `x=1`. Checks for
+        # converged status and that the root was found.
+        a, b = .5, sqrt(3)
+
+        r = root_scalar(function, method=method.__name__, bracket=[a, b], x0=a,
+                        xtol=self.xtol, rtol=self.rtol)
+        assert r.converged
+        assert_allclose(r.root, 1.0, atol=self.xtol, rtol=self.rtol)
+        assert r.method == method.__name__
+
+    @pytest.mark.parametrize('method', bracket_methods)
+    @pytest.mark.parametrize('function', tstutils_functions)
+    def test_basic_individual(self, method, function):
+        # Tests individual bracketing root finders on a small set of simple
+        # problems, each of which has a root at `x=1`. Checks for converged
+        # status and that the root was found.
+        a, b = .5, sqrt(3)
+        root, r = method(function, a, b, xtol=self.xtol, rtol=self.rtol,
+                         full_output=True)
+
+        assert r.converged
+        assert_allclose(root, 1.0, atol=self.xtol, rtol=self.rtol)
+
+    @pytest.mark.parametrize('method', bracket_methods)
+    @pytest.mark.parametrize('function', tstutils_functions)
+    def test_bracket_is_array(self, method, function):
+        # Test bracketing root finders called via `root_scalar` on a small set
+        # of simple problems, each of which has a root at `x=1`. Check that
+        # passing `bracket` as a `ndarray` is accepted and leads to finding the
+        # correct root.
+        a, b = .5, sqrt(3)
+        r = root_scalar(function, method=method.__name__,
+                        bracket=np.array([a, b]), x0=a, xtol=self.xtol,
+                        rtol=self.rtol)
+        assert r.converged
+        assert_allclose(r.root, 1.0, atol=self.xtol, rtol=self.rtol)
+        assert r.method == method.__name__
+
+    @pytest.mark.parametrize('method', bracket_methods)
+    def test_aps_collection(self, method):
+        self.run_collection('aps', method, method.__name__, smoothness=1)
+
+    @pytest.mark.parametrize('method', [zeros.bisect, zeros.ridder,
+                                        zeros.toms748])
+    def test_chandrupatla_collection(self, method):
+        known_fail = {'fun7.4'} if method == zeros.ridder else {}
+        self.run_collection('chandrupatla', method, method.__name__,
+                            known_fail=known_fail)
+
+    @pytest.mark.parametrize('method', bracket_methods)
+    def test_lru_cached_individual(self, method):
+        # check that https://github.com/scipy/scipy/issues/10846 is fixed
+        # (`root_scalar` failed when passed a function that was `@lru_cache`d)
+        a, b = -1, 1
+        root, r = method(f_lrucached, a, b, full_output=True)
+        assert r.converged
+        assert_allclose(root, 0)
+
+    def test_gh_22934(self):
+        with pytest.raises(ValueError, match="maxiter must be >= 0"):
+            zeros.brentq(lambda x: x**2 - 1, -2, 0, maxiter=-1)
+
+
+class TestNewton(TestScalarRootFinders):
+    def test_newton_collections(self):
+        known_fail = ['aps.13.00']
+        known_fail += ['aps.12.05', 'aps.12.17']  # fails under Windows Py27
+        for collection in ['aps', 'complex']:
+            self.run_collection(collection, zeros.newton, 'newton',
+                                smoothness=2, known_fail=known_fail)
+
+    def test_halley_collections(self):
+        known_fail = ['aps.12.06', 'aps.12.07', 'aps.12.08', 'aps.12.09',
+                      'aps.12.10', 'aps.12.11', 'aps.12.12', 'aps.12.13',
+                      'aps.12.14', 'aps.12.15', 'aps.12.16', 'aps.12.17',
+                      'aps.12.18', 'aps.13.00']
+        for collection in ['aps', 'complex']:
+            self.run_collection(collection, zeros.newton, 'halley',
+                                smoothness=2, known_fail=known_fail)
+
+    def test_newton(self):
+        for f, f_1, f_2 in [(f1, f1_1, f1_2), (f2, f2_1, f2_2)]:
+            x = zeros.newton(f, 3, tol=1e-6)
+            assert_allclose(f(x), 0, atol=1e-6)
+            x = zeros.newton(f, 3, x1=5, tol=1e-6)  # secant, x0 and x1
+            assert_allclose(f(x), 0, atol=1e-6)
+            x = zeros.newton(f, 3, fprime=f_1, tol=1e-6)   # newton
+            assert_allclose(f(x), 0, atol=1e-6)
+            x = zeros.newton(f, 3, fprime=f_1, fprime2=f_2, tol=1e-6)  # halley
+            assert_allclose(f(x), 0, atol=1e-6)
+
+    def test_newton_by_name(self):
+        r"""Invoke newton through root_scalar()"""
+        for f, f_1, f_2 in [(f1, f1_1, f1_2), (f2, f2_1, f2_2)]:
+            r = root_scalar(f, method='newton', x0=3, fprime=f_1, xtol=1e-6)
+            assert_allclose(f(r.root), 0, atol=1e-6)
+        for f, f_1, f_2 in [(f1, f1_1, f1_2), (f2, f2_1, f2_2)]:
+            r = root_scalar(f, method='newton', x0=3, xtol=1e-6)  # without f'
+            assert_allclose(f(r.root), 0, atol=1e-6)
+
+    def test_secant_by_name(self):
+        r"""Invoke secant through root_scalar()"""
+        for f, f_1, f_2 in [(f1, f1_1, f1_2), (f2, f2_1, f2_2)]:
+            r = root_scalar(f, method='secant', x0=3, x1=2, xtol=1e-6)
+            assert_allclose(f(r.root), 0, atol=1e-6)
+            r = root_scalar(f, method='secant', x0=3, x1=5, xtol=1e-6)
+            assert_allclose(f(r.root), 0, atol=1e-6)
+        for f, f_1, f_2 in [(f1, f1_1, f1_2), (f2, f2_1, f2_2)]:
+            r = root_scalar(f, method='secant', x0=3, xtol=1e-6)  # without x1
+            assert_allclose(f(r.root), 0, atol=1e-6)
+
+    def test_halley_by_name(self):
+        r"""Invoke halley through root_scalar()"""
+        for f, f_1, f_2 in [(f1, f1_1, f1_2), (f2, f2_1, f2_2)]:
+            r = root_scalar(f, method='halley', x0=3,
+                            fprime=f_1, fprime2=f_2, xtol=1e-6)
+            assert_allclose(f(r.root), 0, atol=1e-6)
+
+    def test_root_scalar_fail(self):
+        message = 'fprime2 must be specified for halley'
+        with pytest.raises(ValueError, match=message):
+            root_scalar(f1, method='halley', fprime=f1_1, x0=3, xtol=1e-6)  # no fprime2
+        message = 'fprime must be specified for halley'
+        with pytest.raises(ValueError, match=message):
+            root_scalar(f1, method='halley', fprime2=f1_2, x0=3, xtol=1e-6)  # no fprime
+
+    def test_array_newton(self):
+        """test newton with array"""
+
+        def f1(x, *a):
+            b = a[0] + x * a[3]
+            return a[1] - a[2] * (np.exp(b / a[5]) - 1.0) - b / a[4] - x
+
+        def f1_1(x, *a):
+            b = a[3] / a[5]
+            return -a[2] * np.exp(a[0] / a[5] + x * b) * b - a[3] / a[4] - 1
+
+        def f1_2(x, *a):
+            b = a[3] / a[5]
+            return -a[2] * np.exp(a[0] / a[5] + x * b) * b**2
+
+        a0 = np.array([
+            5.32725221, 5.48673747, 5.49539973,
+            5.36387202, 4.80237316, 1.43764452,
+            5.23063958, 5.46094772, 5.50512718,
+            5.42046290
+        ])
+        a1 = (np.sin(range(10)) + 1.0) * 7.0
+        args = (a0, a1, 1e-09, 0.004, 10, 0.27456)
+        x0 = [7.0] * 10
+        x = zeros.newton(f1, x0, f1_1, args)
+        x_expected = (
+            6.17264965, 11.7702805, 12.2219954,
+            7.11017681, 1.18151293, 0.143707955,
+            4.31928228, 10.5419107, 12.7552490,
+            8.91225749
+        )
+        assert_allclose(x, x_expected)
+        # test halley's
+        x = zeros.newton(f1, x0, f1_1, args, fprime2=f1_2)
+        assert_allclose(x, x_expected)
+        # test secant
+        x = zeros.newton(f1, x0, args=args)
+        assert_allclose(x, x_expected)
+
+    def test_array_newton_complex(self):
+        def f(x):
+            return x + 1+1j
+
+        def fprime(x):
+            return 1.0
+
+        t = np.full(4, 1j)
+        x = zeros.newton(f, t, fprime=fprime)
+        assert_allclose(f(x), 0.)
+
+        # should work even if x0 is not complex
+        t = np.ones(4)
+        x = zeros.newton(f, t, fprime=fprime)
+        assert_allclose(f(x), 0.)
+
+        x = zeros.newton(f, t)
+        assert_allclose(f(x), 0.)
+
+    def test_array_secant_active_zero_der(self):
+        """test secant doesn't continue to iterate zero derivatives"""
+        x = zeros.newton(lambda x, *a: x*x - a[0], x0=[4.123, 5],
+                         args=[np.array([17, 25])])
+        assert_allclose(x, (4.123105625617661, 5.0))
+
+    def test_array_newton_integers(self):
+        # test secant with float
+        x = zeros.newton(lambda y, z: z - y ** 2, [4.0] * 2,
+                         args=([15.0, 17.0],))
+        assert_allclose(x, (3.872983346207417, 4.123105625617661))
+        # test integer becomes float
+        x = zeros.newton(lambda y, z: z - y ** 2, [4] * 2, args=([15, 17],))
+        assert_allclose(x, (3.872983346207417, 4.123105625617661))
+
+    @pytest.mark.thread_unsafe
+    def test_array_newton_zero_der_failures(self):
+        # test derivative zero warning
+        assert_warns(RuntimeWarning, zeros.newton,
+                     lambda y: y**2 - 2, [0., 0.], lambda y: 2 * y)
+        # test failures and zero_der
+        with pytest.warns(RuntimeWarning):
+            results = zeros.newton(lambda y: y**2 - 2, [0., 0.],
+                                   lambda y: 2*y, full_output=True)
+            assert_allclose(results.root, 0)
+            assert results.zero_der.all()
+            assert not results.converged.any()
+
+    def test_newton_combined(self):
+        def f1(x):
+            return x ** 2 - 2 * x - 1
+        def f1_1(x):
+            return 2 * x - 2
+        def f1_2(x):
+            return 2.0 + 0 * x
+
+        def f1_and_p_and_pp(x):
+            return x**2 - 2*x-1, 2*x-2, 2.0
+
+        sol0 = root_scalar(f1, method='newton', x0=3, fprime=f1_1)
+        sol = root_scalar(f1_and_p_and_pp, method='newton', x0=3, fprime=True)
+        assert_allclose(sol0.root, sol.root, atol=1e-8)
+        assert_equal(2*sol.function_calls, sol0.function_calls)
+
+        sol0 = root_scalar(f1, method='halley', x0=3, fprime=f1_1, fprime2=f1_2)
+        sol = root_scalar(f1_and_p_and_pp, method='halley', x0=3, fprime2=True)
+        assert_allclose(sol0.root, sol.root, atol=1e-8)
+        assert_equal(3*sol.function_calls, sol0.function_calls)
+
+    def test_newton_full_output(self, capsys):
+        # Test the full_output capability, both when converging and not.
+        # Use simple polynomials, to avoid hitting platform dependencies
+        # (e.g., exp & trig) in number of iterations
+
+        x0 = 3
+        expected_counts = [(6, 7), (5, 10), (3, 9)]
+
+        for derivs in range(3):
+            kwargs = {'tol': 1e-6, 'full_output': True, }
+            for k, v in [['fprime', f1_1], ['fprime2', f1_2]][:derivs]:
+                kwargs[k] = v
+
+            x, r = zeros.newton(f1, x0, disp=False, **kwargs)
+            assert_(r.converged)
+            assert_equal(x, r.root)
+            assert_equal((r.iterations, r.function_calls), expected_counts[derivs])
+            if derivs == 0:
+                assert r.function_calls <= r.iterations + 1
+            else:
+                assert_equal(r.function_calls, (derivs + 1) * r.iterations)
+
+            # Now repeat, allowing one fewer iteration to force convergence failure
+            iters = r.iterations - 1
+            x, r = zeros.newton(f1, x0, maxiter=iters, disp=False, **kwargs)
+            assert_(not r.converged)
+            assert_equal(x, r.root)
+            assert_equal(r.iterations, iters)
+
+            if derivs == 1:
+                # Check that the correct Exception is raised and
+                # validate the start of the message.
+                msg = f'Failed to converge after {iters} iterations, value is .*'
+                with pytest.raises(RuntimeError, match=msg):
+                    x, r = zeros.newton(f1, x0, maxiter=iters, disp=True, **kwargs)
+
+    @pytest.mark.thread_unsafe
+    def test_deriv_zero_warning(self):
+        def func(x):
+            return x ** 2 - 2.0
+        def dfunc(x):
+            return 2 * x
+        assert_warns(RuntimeWarning, zeros.newton, func, 0.0, dfunc, disp=False)
+        with pytest.raises(RuntimeError, match='Derivative was zero'):
+            zeros.newton(func, 0.0, dfunc)
+
+    def test_newton_does_not_modify_x0(self):
+        # https://github.com/scipy/scipy/issues/9964
+        x0 = np.array([0.1, 3])
+        x0_copy = x0.copy()  # Copy to test for equality.
+        newton(np.sin, x0, np.cos)
+        assert_array_equal(x0, x0_copy)
+
+    def test_gh17570_defaults(self):
+        # Previously, when fprime was not specified, root_scalar would default
+        # to secant. When x1 was not specified, secant failed.
+        # Check that without fprime, the default is secant if x1 is specified
+        # and newton otherwise.
+        # Also confirm that `x` is always a scalar (gh-21148)
+        def f(x):
+            assert np.isscalar(x)
+            return f1(x)
+
+        res_newton_default = root_scalar(f, method='newton', x0=3, xtol=1e-6)
+        res_secant_default = root_scalar(f, method='secant', x0=3, x1=2,
+                                         xtol=1e-6)
+        # `newton` uses the secant method when `x1` and `x2` are specified
+        res_secant = newton(f, x0=3, x1=2, tol=1e-6, full_output=True)[1]
+
+        # all three found a root
+        assert_allclose(f(res_newton_default.root), 0, atol=1e-6)
+        assert res_newton_default.root.shape == tuple()
+        assert_allclose(f(res_secant_default.root), 0, atol=1e-6)
+        assert res_secant_default.root.shape == tuple()
+        assert_allclose(f(res_secant.root), 0, atol=1e-6)
+        assert res_secant.root.shape == tuple()
+
+        # Defaults are correct
+        assert (res_secant_default.root
+                == res_secant.root
+                != res_newton_default.iterations)
+        assert (res_secant_default.iterations
+                == res_secant_default.function_calls - 1  # true for secant
+                == res_secant.iterations
+                != res_newton_default.iterations
+                == res_newton_default.function_calls/2)  # newton 2-point diff
+
+    @pytest.mark.parametrize('kwargs', [dict(), {'method': 'newton'}])
+    def test_args_gh19090(self, kwargs):
+        def f(x, a, b):
+            assert a == 3
+            assert b == 1
+            return (x ** a - b)
+
+        res = optimize.root_scalar(f, x0=3, args=(3, 1), **kwargs)
+        assert res.converged
+        assert_allclose(res.root, 1)
+
+    @pytest.mark.parametrize('method', ['secant', 'newton'])
+    def test_int_x0_gh19280(self, method):
+        # Originally, `newton` ensured that only floats were passed to the
+        # callable. This was inadvertently changed by gh-17669. Check that
+        # it has been changed back.
+        def f(x):
+            # an integer raised to a negative integer power would fail
+            return x**-2 - 2
+
+        res = optimize.root_scalar(f, x0=1, method=method)
+        assert res.converged
+        assert_allclose(abs(res.root), 2**-0.5)
+        assert res.root.dtype == np.dtype(np.float64)
+
+    def test_newton_special_parameters(self):
+        # give zeros.newton() some strange parameters
+        # and check whether an exception appears
+        with pytest.raises(ValueError, match="tol too small"):
+            zeros.newton(f1, 3, tol=-1e-6)
+
+        with pytest.raises(ValueError, match="maxiter must be greater than 0"):
+            zeros.newton(f1, 3, tol=1e-6, maxiter=-50)
+
+        with pytest.raises(ValueError, match="x1 and x0 must be different" ):
+            zeros.newton(f1, 3, x1=3)
+
+
+def test_gh_5555():
+    root = 0.1
+
+    def f(x):
+        return x - root
+
+    methods = [zeros.bisect, zeros.ridder]
+    xtol = rtol = TOL
+    for method in methods:
+        res = method(f, -1e8, 1e7, xtol=xtol, rtol=rtol)
+        assert_allclose(root, res, atol=xtol, rtol=rtol,
+                        err_msg=f'method {method.__name__}')
+
+
+def test_gh_5557():
+    # Show that without the changes in 5557 brentq and brenth might
+    # only achieve a tolerance of 2*(xtol + rtol*|res|).
+
+    # f linearly interpolates (0, -0.1), (0.5, -0.1), and (1,
+    # 0.4). The important parts are that |f(0)| < |f(1)| (so that
+    # brent takes 0 as the initial guess), |f(0)| < atol (so that
+    # brent accepts 0 as the root), and that the exact root of f lies
+    # more than atol away from 0 (so that brent doesn't achieve the
+    # desired tolerance).
+    def f(x):
+        if x < 0.5:
+            return -0.1
+        else:
+            return x - 0.6
+
+    atol = 0.51
+    rtol = 4 * _FLOAT_EPS
+    methods = [zeros.brentq, zeros.brenth]
+    for method in methods:
+        res = method(f, 0, 1, xtol=atol, rtol=rtol)
+        assert_allclose(0.6, res, atol=atol, rtol=rtol)
+
+
+def test_brent_underflow_in_root_bracketing():
+    # Testing if an interval [a,b] brackets a zero of a function
+    # by checking f(a)*f(b) < 0 is not reliable when the product
+    # underflows/overflows. (reported in issue# 13737)
+
+    underflow_scenario = (-450.0, -350.0, -400.0)
+    overflow_scenario = (350.0, 450.0, 400.0)
+
+    for a, b, root in [underflow_scenario, overflow_scenario]:
+        c = np.exp(root)
+        for method in [zeros.brenth, zeros.brentq]:
+            res = method(lambda x: np.exp(x)-c, a, b)
+            assert_allclose(root, res)
+
+
+class TestRootResults:
+    r = zeros.RootResults(root=1.0, iterations=44, function_calls=46, flag=0,
+                          method="newton")
+
+    def test_repr(self):
+        expected_repr = ("      converged: True\n           flag: converged"
+                         "\n function_calls: 46\n     iterations: 44\n"
+                         "           root: 1.0\n         method: newton")
+        assert_equal(repr(self.r), expected_repr)
+
+    def test_type(self):
+        assert isinstance(self.r, OptimizeResult)
+
+
+def test_complex_halley():
+    """Test Halley's works with complex roots"""
+    def f(x, *a):
+        return a[0] * x**2 + a[1] * x + a[2]
+
+    def f_1(x, *a):
+        return 2 * a[0] * x + a[1]
+
+    def f_2(x, *a):
+        retval = 2 * a[0]
+        try:
+            size = len(x)
+        except TypeError:
+            return retval
+        else:
+            return [retval] * size
+
+    z = complex(1.0, 2.0)
+    coeffs = (2.0, 3.0, 4.0)
+    y = zeros.newton(f, z, args=coeffs, fprime=f_1, fprime2=f_2, tol=1e-6)
+    # (-0.75000000000000078+1.1989578808281789j)
+    assert_allclose(f(y, *coeffs), 0, atol=1e-6)
+    z = [z] * 10
+    coeffs = (2.0, 3.0, 4.0)
+    y = zeros.newton(f, z, args=coeffs, fprime=f_1, fprime2=f_2, tol=1e-6)
+    assert_allclose(f(y, *coeffs), 0, atol=1e-6)
+
+
+@pytest.mark.thread_unsafe
+def test_zero_der_nz_dp(capsys):
+    """Test secant method with a non-zero dp, but an infinite newton step"""
+    # pick a symmetrical functions and choose a point on the side that with dx
+    # makes a secant that is a flat line with zero slope, EG: f = (x - 100)**2,
+    # which has a root at x = 100 and is symmetrical around the line x = 100
+    # we have to pick a really big number so that it is consistently true
+    # now find a point on each side so that the secant has a zero slope
+    dx = np.finfo(float).eps ** 0.33
+    # 100 - p0 = p1 - 100 = p0 * (1 + dx) + dx - 100
+    # -> 200 = p0 * (2 + dx) + dx
+    p0 = (200.0 - dx) / (2.0 + dx)
+    with suppress_warnings() as sup:
+        sup.filter(RuntimeWarning, "RMS of")
+        x = zeros.newton(lambda y: (y - 100.0)**2, x0=[p0] * 10)
+    assert_allclose(x, [100] * 10)
+    # test scalar cases too
+    p0 = (2.0 - 1e-4) / (2.0 + 1e-4)
+    with suppress_warnings() as sup:
+        sup.filter(RuntimeWarning, "Tolerance of")
+        x = zeros.newton(lambda y: (y - 1.0) ** 2, x0=p0, disp=False)
+    assert_allclose(x, 1)
+    with pytest.raises(RuntimeError, match='Tolerance of'):
+        x = zeros.newton(lambda y: (y - 1.0) ** 2, x0=p0, disp=True)
+    p0 = (-2.0 + 1e-4) / (2.0 + 1e-4)
+    with suppress_warnings() as sup:
+        sup.filter(RuntimeWarning, "Tolerance of")
+        x = zeros.newton(lambda y: (y + 1.0) ** 2, x0=p0, disp=False)
+    assert_allclose(x, -1)
+    with pytest.raises(RuntimeError, match='Tolerance of'):
+        x = zeros.newton(lambda y: (y + 1.0) ** 2, x0=p0, disp=True)
+
+
+@pytest.mark.thread_unsafe
+def test_array_newton_failures():
+    """Test that array newton fails as expected"""
+    # p = 0.68  # [MPa]
+    # dp = -0.068 * 1e6  # [Pa]
+    # T = 323  # [K]
+    diameter = 0.10  # [m]
+    # L = 100  # [m]
+    roughness = 0.00015  # [m]
+    rho = 988.1  # [kg/m**3]
+    mu = 5.4790e-04  # [Pa*s]
+    u = 2.488  # [m/s]
+    reynolds_number = rho * u * diameter / mu  # Reynolds number
+
+    def colebrook_eqn(darcy_friction, re, dia):
+        return (1 / np.sqrt(darcy_friction) +
+                2 * np.log10(roughness / 3.7 / dia +
+                             2.51 / re / np.sqrt(darcy_friction)))
+
+    # only some failures
+    with pytest.warns(RuntimeWarning):
+        result = zeros.newton(
+            colebrook_eqn, x0=[0.01, 0.2, 0.02223, 0.3], maxiter=2,
+            args=[reynolds_number, diameter], full_output=True
+        )
+        assert not result.converged.all()
+    # they all fail
+    with pytest.raises(RuntimeError):
+        result = zeros.newton(
+            colebrook_eqn, x0=[0.01] * 2, maxiter=2,
+            args=[reynolds_number, diameter], full_output=True
+        )
+
+
+# this test should **not** raise a RuntimeWarning
+def test_gh8904_zeroder_at_root_fails():
+    """Test that Newton or Halley don't warn if zero derivative at root"""
+
+    # a function that has a zero derivative at it's root
+    def f_zeroder_root(x):
+        return x**3 - x**2
+
+    # should work with secant
+    r = zeros.newton(f_zeroder_root, x0=0)
+    assert_allclose(r, 0, atol=zeros._xtol, rtol=zeros._rtol)
+    # test again with array
+    r = zeros.newton(f_zeroder_root, x0=[0]*10)
+    assert_allclose(r, 0, atol=zeros._xtol, rtol=zeros._rtol)
+
+    # 1st derivative
+    def fder(x):
+        return 3 * x**2 - 2 * x
+
+    # 2nd derivative
+    def fder2(x):
+        return 6*x - 2
+
+    # should work with newton and halley
+    r = zeros.newton(f_zeroder_root, x0=0, fprime=fder)
+    assert_allclose(r, 0, atol=zeros._xtol, rtol=zeros._rtol)
+    r = zeros.newton(f_zeroder_root, x0=0, fprime=fder,
+                     fprime2=fder2)
+    assert_allclose(r, 0, atol=zeros._xtol, rtol=zeros._rtol)
+    # test again with array
+    r = zeros.newton(f_zeroder_root, x0=[0]*10, fprime=fder)
+    assert_allclose(r, 0, atol=zeros._xtol, rtol=zeros._rtol)
+    r = zeros.newton(f_zeroder_root, x0=[0]*10, fprime=fder,
+                     fprime2=fder2)
+    assert_allclose(r, 0, atol=zeros._xtol, rtol=zeros._rtol)
+
+    # also test that if a root is found we do not raise RuntimeWarning even if
+    # the derivative is zero, EG: at x = 0.5, then fval = -0.125 and
+    # fder = -0.25 so the next guess is 0.5 - (-0.125/-0.5) = 0 which is the
+    # root, but if the solver continued with that guess, then it will calculate
+    # a zero derivative, so it should return the root w/o RuntimeWarning
+    r = zeros.newton(f_zeroder_root, x0=0.5, fprime=fder)
+    assert_allclose(r, 0, atol=zeros._xtol, rtol=zeros._rtol)
+    # test again with array
+    r = zeros.newton(f_zeroder_root, x0=[0.5]*10, fprime=fder)
+    assert_allclose(r, 0, atol=zeros._xtol, rtol=zeros._rtol)
+    # doesn't apply to halley
+
+
+def test_gh_8881():
+    r"""Test that Halley's method realizes that the 2nd order adjustment
+    is too big and drops off to the 1st order adjustment."""
+    n = 9
+
+    def f(x):
+        return power(x, 1.0/n) - power(n, 1.0/n)
+
+    def fp(x):
+        return power(x, (1.0-n)/n)/n
+
+    def fpp(x):
+        return power(x, (1.0-2*n)/n) * (1.0/n) * (1.0-n)/n
+
+    x0 = 0.1
+    # The root is at x=9.
+    # The function has positive slope, x0 < root.
+    # Newton succeeds in 8 iterations
+    rt, r = newton(f, x0, fprime=fp, full_output=True)
+    assert r.converged
+    # Before the Issue 8881/PR 8882, halley would send x in the wrong direction.
+    # Check that it now succeeds.
+    rt, r = newton(f, x0, fprime=fp, fprime2=fpp, full_output=True)
+    assert r.converged
+
+
+def test_gh_9608_preserve_array_shape():
+    """
+    Test that shape is preserved for array inputs even if fprime or fprime2 is
+    scalar
+    """
+    def f(x):
+        return x**2
+
+    def fp(x):
+        return 2 * x
+
+    def fpp(x):
+        return 2
+
+    x0 = np.array([-2], dtype=np.float32)
+    rt, r = newton(f, x0, fprime=fp, fprime2=fpp, full_output=True)
+    assert r.converged
+
+    x0_array = np.array([-2, -3], dtype=np.float32)
+    # This next invocation should fail
+    with pytest.raises(IndexError):
+        result = zeros.newton(
+            f, x0_array, fprime=fp, fprime2=fpp, full_output=True
+        )
+
+    def fpp_array(x):
+        return np.full(np.shape(x), 2, dtype=np.float32)
+
+    result = zeros.newton(
+        f, x0_array, fprime=fp, fprime2=fpp_array, full_output=True
+    )
+    assert result.converged.all()
+
+
+@pytest.mark.parametrize(
+    "maximum_iterations,flag_expected",
+    [(10, zeros.CONVERR), (100, zeros.CONVERGED)])
+def test_gh9254_flag_if_maxiter_exceeded(maximum_iterations, flag_expected):
+    """
+    Test that if the maximum iterations is exceeded that the flag is not
+    converged.
+    """
+    result = zeros.brentq(
+        lambda x: ((1.2*x - 2.3)*x + 3.4)*x - 4.5,
+        -30, 30, (), 1e-6, 1e-6, maximum_iterations,
+        full_output=True, disp=False)
+    assert result[1].flag == flag_expected
+    if flag_expected == zeros.CONVERR:
+        # didn't converge because exceeded maximum iterations
+        assert result[1].iterations == maximum_iterations
+    elif flag_expected == zeros.CONVERGED:
+        # converged before maximum iterations
+        assert result[1].iterations < maximum_iterations
+
+
+@pytest.mark.thread_unsafe
+def test_gh9551_raise_error_if_disp_true():
+    """Test that if disp is true then zero derivative raises RuntimeError"""
+
+    def f(x):
+        return x*x + 1
+
+    def f_p(x):
+        return 2*x
+
+    assert_warns(RuntimeWarning, zeros.newton, f, 1.0, f_p, disp=False)
+    with pytest.raises(
+            RuntimeError,
+            match=r'^Derivative was zero\. Failed to converge after \d+ iterations, '
+                  r'value is [+-]?\d*\.\d+\.$'):
+        zeros.newton(f, 1.0, f_p)
+    root = zeros.newton(f, complex(10.0, 10.0), f_p)
+    assert_allclose(root, complex(0.0, 1.0))
+
+
+@pytest.mark.parametrize('solver_name',
+                         ['brentq', 'brenth', 'bisect', 'ridder', 'toms748'])
+def test_gh3089_8394(solver_name):
+    # gh-3089 and gh-8394 reported that bracketing solvers returned incorrect
+    # results when they encountered NaNs. Check that this is resolved.
+    def f(x):
+        return np.nan
+
+    solver = getattr(zeros, solver_name)
+    with pytest.raises(ValueError, match="The function value at x..."):
+        solver(f, 0, 1)
+
+
+@pytest.mark.parametrize('method',
+                         ['brentq', 'brenth', 'bisect', 'ridder', 'toms748'])
+def test_gh18171(method):
+    # gh-3089 and gh-8394 reported that bracketing solvers returned incorrect
+    # results when they encountered NaNs. Check that `root_scalar` returns
+    # normally but indicates that convergence was unsuccessful. See gh-18171.
+    def f(x):
+        f._count += 1
+        return np.nan
+    f._count = 0
+
+    res = root_scalar(f, bracket=(0, 1), method=method)
+    assert res.converged is False
+    assert res.flag.startswith("The function value at x")
+    assert res.function_calls == f._count
+    assert str(res.root) in res.flag
+
+
+@pytest.mark.parametrize('solver_name',
+                         ['brentq', 'brenth', 'bisect', 'ridder', 'toms748'])
+@pytest.mark.parametrize('rs_interface', [True, False])
+def test_function_calls(solver_name, rs_interface):
+    # There do not appear to be checks that the bracketing solvers report the
+    # correct number of function evaluations. Check that this is the case.
+    solver = ((lambda f, a, b, **kwargs: root_scalar(f, bracket=(a, b)))
+              if rs_interface else getattr(zeros, solver_name))
+
+    def f(x):
+        f.calls += 1
+        return x**2 - 1
+    f.calls = 0
+
+    res = solver(f, 0, 10, full_output=True)
+
+    if rs_interface:
+        assert res.function_calls == f.calls
+    else:
+        assert res[1].function_calls == f.calls
+
+
+@pytest.mark.thread_unsafe
+def test_gh_14486_converged_false():
+    """Test that zero slope with secant method results in a converged=False"""
+    def lhs(x):
+        return x * np.exp(-x*x) - 0.07
+
+    with pytest.warns(RuntimeWarning, match='Tolerance of'):
+        res = root_scalar(lhs, method='secant', x0=-0.15, x1=1.0)
+    assert not res.converged
+    assert res.flag == 'convergence error'
+
+    with pytest.warns(RuntimeWarning, match='Tolerance of'):
+        res = newton(lhs, x0=-0.15, x1=1.0, disp=False, full_output=True)[1]
+    assert not res.converged
+    assert res.flag == 'convergence error'
+
+
+@pytest.mark.parametrize('solver_name',
+                         ['brentq', 'brenth', 'bisect', 'ridder', 'toms748'])
+@pytest.mark.parametrize('rs_interface', [True, False])
+def test_gh5584(solver_name, rs_interface):
+    # gh-5584 reported that an underflow can cause sign checks in the algorithm
+    # to fail. Check that this is resolved.
+    solver = ((lambda f, a, b, **kwargs: root_scalar(f, bracket=(a, b)))
+              if rs_interface else getattr(zeros, solver_name))
+
+    def f(x):
+        return 1e-200*x
+
+    # Report failure when signs are the same
+    with pytest.raises(ValueError, match='...must have different signs'):
+        solver(f, -0.5, -0.4, full_output=True)
+
+    # Solve successfully when signs are different
+    res = solver(f, -0.5, 0.4, full_output=True)
+    res = res if rs_interface else res[1]
+    assert res.converged
+    assert_allclose(res.root, 0, atol=1e-8)
+
+    # Solve successfully when one side is negative zero
+    res = solver(f, -0.5, float('-0.0'), full_output=True)
+    res = res if rs_interface else res[1]
+    assert res.converged
+    assert_allclose(res.root, 0, atol=1e-8)
+
+
+def test_gh13407():
+    # gh-13407 reported that the message produced by `scipy.optimize.toms748`
+    # when `rtol < eps` is incorrect, and also that toms748 is unusual in
+    # accepting `rtol` as low as eps while other solvers raise at 4*eps. Check
+    # that the error message has been corrected and that `rtol=eps` can produce
+    # a lower function value than `rtol=4*eps`.
+    def f(x):
+        return x**3 - 2*x - 5
+
+    xtol = 1e-300
+    eps = np.finfo(float).eps
+    x1 = zeros.toms748(f, 1e-10, 1e10, xtol=xtol, rtol=1*eps)
+    f1 = f(x1)
+    x4 = zeros.toms748(f, 1e-10, 1e10, xtol=xtol, rtol=4*eps)
+    f4 = f(x4)
+    assert f1 < f4
+
+    # using old-style syntax to get exactly the same message
+    message = fr"rtol too small \({eps/2:g} < {eps:g}\)"
+    with pytest.raises(ValueError, match=message):
+        zeros.toms748(f, 1e-10, 1e10, xtol=xtol, rtol=eps/2)
+
+
+def test_newton_complex_gh10103():
+    # gh-10103 reported a problem when `newton` is pass a Python complex x0,
+    # no `fprime` (secant method), and no `x1` (`x1` must be constructed).
+    # Check that this is resolved.
+    def f(z):
+        return z - 1
+    res = newton(f, 1+1j)
+    assert_allclose(res, 1, atol=1e-12)
+
+    res = root_scalar(f, x0=1+1j, x1=2+1.5j, method='secant')
+    assert_allclose(res.root, 1, atol=1e-12)
+
+
+@pytest.mark.parametrize('method', all_methods)
+def test_maxiter_int_check_gh10236(method):
+    # gh-10236 reported that the error message when `maxiter` is not an integer
+    # was difficult to interpret. Check that this was resolved (by gh-10907).
+    message = "'float' object cannot be interpreted as an integer"
+    with pytest.raises(TypeError, match=message):
+        method(f1, 0.0, 1.0, maxiter=72.45)
+
+@pytest.mark.parametrize("method", [zeros.bisect, zeros.ridder,
+                                    zeros.brentq, zeros.brenth])
+def test_bisect_special_parameter(method):
+    # give some zeros method strange parameters
+    # and check whether an exception appears
+    root = 0.1
+    args = (1e-09, 0.004, 10, 0.27456)
+    rtolbad = 4 * np.finfo(float).eps / 2
+
+    def f(x):
+        return x - root
+
+    with pytest.raises(ValueError, match="xtol too small"):
+       method(f, -1e8, 1e7, args=args, xtol=-1e-6, rtol=TOL)
+    with pytest.raises(ValueError, match="rtol too small"):
+       method(f, -1e8, 1e7, args=args, xtol=1e-6, rtol=rtolbad)