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gh-119372: recover inf's and zeros in _Py_c_quot #119457

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Merged
merged 8 commits into from
Jun 29, 2024
Merged

gh-119372: recover inf's and zeros in _Py_c_quot #119457

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06ac53d
gh-119372: recover inf's and zeros in _Py_c_quot
skirpichev May 22, 2024
fc3f91d
Tests reformatted
skirpichev May 23, 2024
99669a1
Address review: use Py_IS_* macros
skirpichev May 27, 2024
d4718bc
Merge branch 'main' into fix-complex-tdiv-119372
skirpichev May 27, 2024
b1b3e76
Merge branch 'main' into fix-complex-tdiv-119372
skirpichev May 28, 2024
f6f5510
Merge branch 'master' into fix-complex-tdiv-119372
skirpichev May 30, 2024
1c9ccc4
Partially revert 99669a1 (don't use Py_IS_* macros)
skirpichev May 30, 2024
6e17df6
Merge branch 'main' into fix-complex-tdiv-119372
skirpichev Jun 18, 2024
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31 changes: 31 additions & 0 deletions Lib/test/test_complex.py
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Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,10 @@ def assertFloatsAreIdentical(self, x, y):
msg += ': zeros have different signs'
self.fail(msg.format(x, y))

def assertComplexesAreIdentical(self, x, y):
self.assertFloatsAreIdentical(x.real, y.real)
self.assertFloatsAreIdentical(x.imag, y.imag)

def assertClose(self, x, y, eps=1e-9):
"""Return true iff complexes x and y "are close"."""
self.assertCloseAbs(x.real, y.real, eps)
Expand Down Expand Up @@ -139,6 +143,33 @@ def test_truediv(self):
self.assertTrue(isnan(z.real))
self.assertTrue(isnan(z.imag))

self.assertComplexesAreIdentical(complex(INF, 1)/(0.0+1j),
complex(NAN, -INF))

# test recover of infs if numerator has infs and denominator is finite
self.assertComplexesAreIdentical(complex(INF, -INF)/(1+0j),
complex(INF, -INF))
self.assertComplexesAreIdentical(complex(INF, INF)/(0.0+1j),
complex(INF, -INF))
self.assertComplexesAreIdentical(complex(NAN, INF)/complex(2**1000, 2**-1000),
complex(INF, INF))
self.assertComplexesAreIdentical(complex(INF, NAN)/complex(2**1000, 2**-1000),
complex(INF, -INF))

# test recover of zeros if denominator is infinite
self.assertComplexesAreIdentical((1+1j)/complex(INF, INF), (0.0+0j))
self.assertComplexesAreIdentical((1+1j)/complex(INF, -INF), (0.0+0j))
self.assertComplexesAreIdentical((1+1j)/complex(-INF, INF),
complex(0.0, -0.0))
self.assertComplexesAreIdentical((1+1j)/complex(-INF, -INF),
complex(-0.0, 0))
self.assertComplexesAreIdentical((INF+1j)/complex(INF, INF),
complex(NAN, NAN))
self.assertComplexesAreIdentical(complex(1, INF)/complex(INF, INF),
complex(NAN, NAN))
self.assertComplexesAreIdentical(complex(INF, 1)/complex(1, INF),
complex(NAN, NAN))

def test_truediv_zero_division(self):
for a, b in ZERO_DIVISION:
with self.assertRaises(ZeroDivisionError):
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2024-05-22-12-49-03.gh-issue-119372.PXig1R.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Correct invalid corner cases in complex division (resulted in ``(nan+nanj)``
output), e.g. ``1/complex('(inf+infj)')``. Patch by Sergey B Kirpichev.
25 changes: 23 additions & 2 deletions Objects/complexobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -88,8 +88,7 @@ _Py_c_quot(Py_complex a, Py_complex b)
* numerators and denominator by whichever of {b.real, b.imag} has
* larger magnitude. The earliest reference I found was to CACM
* Algorithm 116 (Complex Division, Robert L. Smith, Stanford
* University). As usual, though, we're still ignoring all IEEE
* endcases.
* University).
*/
Py_complex r; /* the result */
const double abs_breal = b.real < 0 ? -b.real : b.real;
Expand Down Expand Up @@ -120,6 +119,28 @@ _Py_c_quot(Py_complex a, Py_complex b)
/* At least one of b.real or b.imag is a NaN */
r.real = r.imag = Py_NAN;
}

/* Recover infinities and zeros that computed as nan+nanj. See e.g.
the C11, Annex G.5.2, routine _Cdivd(). */
if (isnan(r.real) && isnan(r.imag)) {
if ((isinf(a.real) || isinf(a.imag))
&& isfinite(b.real) && isfinite(b.imag))
{
const double x = copysign(isinf(a.real) ? 1.0 : 0.0, a.real);
const double y = copysign(isinf(a.imag) ? 1.0 : 0.0, a.imag);
r.real = Py_INFINITY * (x*b.real + y*b.imag);
r.imag = Py_INFINITY * (y*b.real - x*b.imag);
}
else if ((isinf(abs_breal) || isinf(abs_bimag))
&& isfinite(a.real) && isfinite(a.imag))
{
const double x = copysign(isinf(b.real) ? 1.0 : 0.0, b.real);
const double y = copysign(isinf(b.imag) ? 1.0 : 0.0, b.imag);
r.real = 0.0 * (a.real*x + a.imag*y);
r.imag = 0.0 * (a.imag*x - a.real*y);
}
}

return r;
}
#ifdef _M_ARM64
Expand Down
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