image-match/python/py/Lib/site-packages/scipy/special/tests/test_logit.py

import numpy as np
from numpy.testing import assert_equal, assert_allclose
from scipy.special import logit, expit, log_expit


class TestLogit:

    def check_logit_out(self, a, expected):
        actual = logit(a)
        assert_equal(actual.dtype, a.dtype)
        rtol = 16*np.finfo(a.dtype).eps
        assert_allclose(actual, expected, rtol=rtol)

    def test_float32(self):
        a = np.concatenate((np.linspace(0, 1, 10, dtype=np.float32),
                            [np.float32(0.0001), np.float32(0.49999),
                             np.float32(0.50001)]))
        # Expected values computed with mpmath from float32 inputs, e.g.
        #   from mpmath import mp
        #   mp.dps = 200
        #   a = np.float32(1/9)
        #   print(np.float32(mp.log(a) - mp.log1p(-a)))
        # prints `-2.0794415`.
        expected = np.array([-np.inf, -2.0794415, -1.2527629, -6.9314712e-01,
                             -2.2314353e-01,  2.2314365e-01,  6.9314724e-01,
                             1.2527630, 2.0794415, np.inf,
                             -9.2102404, -4.0054321e-05, 4.0054321e-05],
                            dtype=np.float32)
        self.check_logit_out(a, expected)

    def test_float64(self):
        a = np.concatenate((np.linspace(0, 1, 10, dtype=np.float64),
                            [1e-8, 0.4999999999999, 0.50000000001]))
        # Expected values computed with mpmath.
        expected = np.array([-np.inf,
                             -2.079441541679836,
                             -1.252762968495368,
                             -0.6931471805599454,
                             -0.22314355131420985,
                             0.22314355131420985,
                             0.6931471805599452,
                             1.2527629684953674,
                             2.0794415416798353,
                             np.inf,
                             -18.420680733952366,
                             -3.999023334699814e-13,
                             4.000000330961484e-11])
        self.check_logit_out(a, expected)

    def test_nan(self):
        expected = np.array([np.nan]*4)
        with np.errstate(invalid='ignore'):
            actual = logit(np.array([-3., -2., 2., 3.]))

        assert_equal(expected, actual)


class TestExpit:
    def check_expit_out(self, dtype, expected):
        a = np.linspace(-4, 4, 10)
        a = np.array(a, dtype=dtype)
        actual = expit(a)
        assert_allclose(actual, expected, atol=1.5e-7, rtol=0)
        assert_equal(actual.dtype, np.dtype(dtype))

    def test_float32(self):
        expected = np.array([0.01798621, 0.04265125,
                            0.09777259, 0.20860852,
                            0.39068246, 0.60931754,
                            0.79139149, 0.9022274,
                            0.95734876, 0.98201376], dtype=np.float32)
        self.check_expit_out('f4', expected)

    def test_float64(self):
        expected = np.array([0.01798621, 0.04265125,
                            0.0977726, 0.20860853,
                            0.39068246, 0.60931754,
                            0.79139147, 0.9022274,
                            0.95734875, 0.98201379])
        self.check_expit_out('f8', expected)

    def test_large(self):
        for dtype in (np.float32, np.float64, np.longdouble):
            for n in (88, 89, 709, 710, 11356, 11357):
                n = np.array(n, dtype=dtype)
                assert_allclose(expit(n), 1.0, atol=1e-20)
                assert_allclose(expit(-n), 0.0, atol=1e-20)
                assert_equal(expit(n).dtype, dtype)
                assert_equal(expit(-n).dtype, dtype)


class TestLogExpit:

    def test_large_negative(self):
        x = np.array([-10000.0, -750.0, -500.0, -35.0])
        y = log_expit(x)
        assert_equal(y, x)

    def test_large_positive(self):
        x = np.array([750.0, 1000.0, 10000.0])
        y = log_expit(x)
        # y will contain -0.0, and -0.0 is used in the expected value,
        # but assert_equal does not check the sign of zeros, and I don't
        # think the sign is an essential part of the test (i.e. it would
        # probably be OK if log_expit(1000) returned 0.0 instead of -0.0).
        assert_equal(y, np.array([-0.0, -0.0, -0.0]))

    def test_basic_float64(self):
        x = np.array([-32, -20, -10, -3, -1, -0.1, -1e-9,
                      0, 1e-9, 0.1, 1, 10, 100, 500, 710, 725, 735])
        y = log_expit(x)
        #
        # Expected values were computed with mpmath:
        #
        #   import mpmath
        #
        #   mpmath.mp.dps = 100
        #
        #   def mp_log_expit(x):
        #       return -mpmath.log1p(mpmath.exp(-x))
        #
        #   expected = [float(mp_log_expit(t)) for t in x]
        #
        expected = [-32.000000000000014, -20.000000002061153,
                    -10.000045398899218, -3.048587351573742,
                    -1.3132616875182228, -0.7443966600735709,
                    -0.6931471810599453, -0.6931471805599453,
                    -0.6931471800599454, -0.6443966600735709,
                    -0.3132616875182228, -4.539889921686465e-05,
                    -3.720075976020836e-44, -7.124576406741286e-218,
                    -4.47628622567513e-309, -1.36930634e-315,
                    -6.217e-320]

        # When tested locally, only one value in y was not exactly equal to
        # expected.  That was for x=1, and the y value differed from the
        # expected by 1 ULP.  For this test, however, I'll use rtol=1e-15.
        assert_allclose(y, expected, rtol=1e-15)

    def test_basic_float32(self):
        x = np.array([-32, -20, -10, -3, -1, -0.1, -1e-9,
                      0, 1e-9, 0.1, 1, 10, 100], dtype=np.float32)
        y = log_expit(x)
        #
        # Expected values were computed with mpmath:
        #
        #   import mpmath
        #
        #   mpmath.mp.dps = 100
        #
        #   def mp_log_expit(x):
        #       return -mpmath.log1p(mpmath.exp(-x))
        #
        #   expected = [np.float32(mp_log_expit(t)) for t in x]
        #
        expected = np.array([-32.0, -20.0, -10.000046, -3.0485873,
                             -1.3132616, -0.7443967, -0.6931472,
                             -0.6931472, -0.6931472, -0.64439666,
                             -0.3132617, -4.5398898e-05, -3.8e-44],
                            dtype=np.float32)

        assert_allclose(y, expected, rtol=5e-7)