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gh-120010: Fix invalid (nan+nanj) results in _Py_c_prod() (GH-120287)

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In some cases, previously computed as (nan+nanj), we could recover
meaningful component values in the result, see e.g. the C11, Annex
G.5.1, routine _Cmultd():

>>> z = 1e300+1j
>>> z*(nan+infj)  # was (nan+nanj)
(-inf+infj)

That also fix some complex powers for small integer exponents, computed
with optimized algorithm (by squaring):

>>> z**5  # was (nan+nanj)
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    z**5
    ~^^~
OverflowError: complex exponentiation
This commit is contained in:
Sergey B Kirpichev 2024-12-06 13:28:32 +03:00 • committed by GitHub
parent e991ac8f20
commit 8b7c194c7b
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3 changed files with 75 additions and 4 deletions
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17
Lib/test/test_complex.py
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@ -299,6 +299,22 @@ class ComplexTest(ComplexesAreIdenticalMixin, unittest.TestCase):
self.assertRaises(TypeError, operator.mul, 1j, None)
self.assertRaises(TypeError, operator.mul, None, 1j)
for z, w, r in [(1e300+1j, complex(INF, INF), complex(NAN, INF)),
(1e300+1j, complex(NAN, INF), complex(-INF, INF)),
(1e300+1j, complex(INF, NAN), complex(INF, INF)),
(complex(INF, 1), complex(NAN, INF), complex(NAN, INF)),
(complex(INF, 1), complex(INF, NAN), complex(INF, NAN)),
(complex(NAN, 1), complex(1, INF), complex(-INF, NAN)),
(complex(1, NAN), complex(1, INF), complex(NAN, INF)),
(complex(1e200, NAN), complex(1e200, NAN), complex(INF, NAN)),
(complex(1e200, NAN), complex(NAN, 1e200), complex(NAN, INF)),
(complex(NAN, 1e200), complex(1e200, NAN), complex(NAN, INF)),
(complex(NAN, 1e200), complex(NAN, 1e200), complex(-INF, NAN)),
(complex(NAN, NAN), complex(NAN, NAN), complex(NAN, NAN))]:
with self.subTest(z=z, w=w, r=r):
self.assertComplexesAreIdentical(z * w, r)
self.assertComplexesAreIdentical(w * z, r)
def test_mod(self):
# % is no longer supported on complex numbers
with self.assertRaises(TypeError):
@ -340,6 +356,7 @@ class ComplexTest(ComplexesAreIdenticalMixin, unittest.TestCase):
self.assertAlmostEqual(pow(1j, 200), 1)
self.assertRaises(ValueError, pow, 1+1j, 1+1j, 1+1j)
self.assertRaises(OverflowError, pow, 1e200+1j, 1e200+1j)
self.assertRaises(OverflowError, pow, 1e200+1j, 5)
self.assertRaises(TypeError, pow, 1j, None)
self.assertRaises(TypeError, pow, None, 1j)
self.assertAlmostEqual(pow(1j, 0.5), 0.7071067811865476+0.7071067811865475j)