90 lines
3.0 KiB
Python
90 lines
3.0 KiB
Python
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import numpy as np
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from numpy.testing import assert_allclose, assert_equal
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import pytest
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import scipy.special as sc
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class TestInverseErrorFunction:
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def test_compliment(self):
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# Test erfcinv(1 - x) == erfinv(x)
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x = np.linspace(-1, 1, 101)
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assert_allclose(sc.erfcinv(1 - x), sc.erfinv(x), rtol=0, atol=1e-15)
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def test_literal_values(self):
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# The expected values were calculated with mpmath:
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#
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# import mpmath
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# mpmath.mp.dps = 200
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# for y in [0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9]:
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# x = mpmath.erfinv(y)
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# print(x)
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#
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y = np.array([0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9])
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actual = sc.erfinv(y)
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expected = [
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0.0,
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0.08885599049425769,
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0.1791434546212917,
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0.2724627147267543,
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0.37080715859355795,
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0.4769362762044699,
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0.5951160814499948,
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0.7328690779592167,
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0.9061938024368233,
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1.1630871536766743,
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]
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assert_allclose(actual, expected, rtol=0, atol=1e-15)
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@pytest.mark.parametrize(
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'f, x, y',
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[
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(sc.erfinv, -1, -np.inf),
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(sc.erfinv, 0, 0),
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(sc.erfinv, 1, np.inf),
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(sc.erfinv, -100, np.nan),
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(sc.erfinv, 100, np.nan),
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(sc.erfcinv, 0, np.inf),
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(sc.erfcinv, 1, -0.0),
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(sc.erfcinv, 2, -np.inf),
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(sc.erfcinv, -100, np.nan),
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(sc.erfcinv, 100, np.nan),
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],
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ids=[
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'erfinv at lower bound',
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'erfinv at midpoint',
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'erfinv at upper bound',
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'erfinv below lower bound',
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'erfinv above upper bound',
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'erfcinv at lower bound',
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'erfcinv at midpoint',
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'erfcinv at upper bound',
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'erfcinv below lower bound',
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'erfcinv above upper bound',
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]
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)
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def test_domain_bounds(self, f, x, y):
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assert_equal(f(x), y)
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def test_erfinv_asympt(self):
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# regression test for gh-12758: erfinv(x) loses precision at small x
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# expected values precomputed with mpmath:
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# >>> mpmath.mp.dps = 100
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# >>> expected = [float(mpmath.erfinv(t)) for t in x]
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x = np.array([1e-20, 1e-15, 1e-14, 1e-10, 1e-8, 0.9e-7, 1.1e-7, 1e-6])
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expected = np.array([8.86226925452758e-21,
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8.862269254527581e-16,
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8.86226925452758e-15,
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8.862269254527581e-11,
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8.86226925452758e-09,
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7.97604232907484e-08,
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9.74849617998037e-08,
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8.8622692545299e-07])
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assert_allclose(sc.erfinv(x), expected,
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rtol=1e-15)
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# also test the roundtrip consistency
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assert_allclose(sc.erf(sc.erfinv(x)),
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x,
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rtol=5e-15)
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