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- # Tests for a few of the "double-double" C++ functions defined in
- # special/cephes/dd_real.h. Prior to gh-20390 which translated these
- # functions from C to C++, there were test cases for _dd_expm1. It
- # was determined that this function is not used anywhere internally
- # in SciPy, so this function was not translated.
- import pytest
- from numpy.testing import assert_allclose
- from scipy.special._test_internal import _dd_exp, _dd_log
- # Each tuple in test_data contains:
- # (dd_func, xhi, xlo, expected_yhi, expected_ylo)
- # The expected values were computed with mpmath, e.g.
- #
- # import mpmath
- # mpmath.mp.dps = 100
- # xhi = 10.0
- # xlo = 0.0
- # x = mpmath.mpf(xhi) + mpmath.mpf(xlo)
- # y = mpmath.log(x)
- # expected_yhi = float(y)
- # expected_ylo = float(y - expected_yhi)
- #
- test_data = [
- (_dd_exp, -0.3333333333333333, -1.850371707708594e-17,
- 0.7165313105737893, -2.0286948382455594e-17),
- (_dd_exp, 0.0, 0.0, 1.0, 0.0),
- (_dd_exp, 10.0, 0.0, 22026.465794806718, -1.3780134700517372e-12),
- (_dd_log, 0.03125, 0.0, -3.4657359027997265, -4.930038229799327e-18),
- (_dd_log, 10.0, 0.0, 2.302585092994046, -2.1707562233822494e-16),
- ]
- @pytest.mark.parametrize('dd_func, xhi, xlo, expected_yhi, expected_ylo',
- test_data)
- def test_dd(dd_func, xhi, xlo, expected_yhi, expected_ylo):
- yhi, ylo = dd_func(xhi, xlo)
- assert yhi == expected_yhi, (f"high double ({yhi}) does not equal the "
- f"expected value {expected_yhi}")
- assert_allclose(ylo, expected_ylo, rtol=5e-15)
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