https://github.com/python/cpython/commit/c4333a12708a917d1cfb6418c04be45793ecc392
commit: c4333a12708a917d1cfb6418c04be45793ecc392
branch: main
author: Sergey B Kirpichev <[email protected]>
committer: vstinner <[email protected]>
date: 2026-03-10T17:40:51+01:00
summary:
gh-144173: fix flaky test_complex.test_truediv() (#144355)
Previously, component-wise relative error bound was tested. However,
such bound can't exist already for complex multiplication as one can be
used to perform subtraction of floating-point numbers, e.g. x and y for
z0=1+1j and z1=x+yj.
```pycon
>>> x, y = 1e-9+1j, 1+1j
>>> a = x*y*y.conjugate()/2;a
(1.0000000272292198e-09+1j)
>>> b = x*(y*y.conjugate()/2);b
(1e-09+1j)
>>> b == x
True
>>> (a.real-b.real)/math.ulp(b.real)
131672427.0
```
files:
M Lib/test/test_complex.py
diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
index 0c7e7341f13d4e..bee2aceb187027 100644
--- a/Lib/test/test_complex.py
+++ b/Lib/test/test_complex.py
@@ -72,8 +72,8 @@ def assertAlmostEqual(self, a, b):
else:
unittest.TestCase.assertAlmostEqual(self, a, b)
- def assertCloseAbs(self, x, y, eps=1e-9):
- """Return true iff floats x and y "are close"."""
+ def assertClose(self, x, y, eps=1e-9):
+ """Return true iff complexes x and y "are close"."""
# put the one with larger magnitude second
if abs(x) > abs(y):
x, y = y, x
@@ -82,26 +82,15 @@ def assertCloseAbs(self, x, y, eps=1e-9):
if x == 0:
return abs(y) < eps
# check that relative difference < eps
- self.assertTrue(abs((x-y)/y) < eps)
-
- def assertClose(self, x, y, eps=1e-9):
- """Return true iff complexes x and y "are close"."""
- self.assertCloseAbs(x.real, y.real, eps)
- self.assertCloseAbs(x.imag, y.imag, eps)
+ self.assertTrue(abs(x-y)/abs(y) < eps)
def check_div(self, x, y):
"""Compute complex z=x*y, and check that z/x==y and z/y==x."""
z = x * y
- if x != 0:
- q = z / x
- self.assertClose(q, y)
- q = z.__truediv__(x)
- self.assertClose(q, y)
- if y != 0:
- q = z / y
- self.assertClose(q, x)
- q = z.__truediv__(y)
- self.assertClose(q, x)
+ if x:
+ self.assertClose(z / x, y)
+ if y:
+ self.assertClose(z / y, x)
def test_truediv(self):
simple_real = [float(i) for i in range(-5, 6)]
@@ -115,10 +104,20 @@ def test_truediv(self):
self.check_div(complex(1e200, 1e200), 1+0j)
self.check_div(complex(1e-200, 1e-200), 1+0j)
+ # Smith's algorithm has several sources of inaccuracy
+ # for components of the result. In examples below,
+ # it's cancellation of digits in computation of sum.
+ self.check_div(1e-09+1j, 1+1j)
+ self.check_div(8.289760544677449e-09+0.13257307440728516j,
+ 0.9059966714925808+0.5054864708672686j)
+
# Just for fun.
for i in range(100):
- self.check_div(complex(random(), random()),
- complex(random(), random()))
+ x = complex(random(), random())
+ y = complex(random(), random())
+ self.check_div(x, y)
+ y = complex(1e10*y.real, y.imag)
+ self.check_div(x, y)
self.assertAlmostEqual(complex.__truediv__(2+0j, 1+1j), 1-1j)
self.assertRaises(TypeError, operator.truediv, 1j, None)
@@ -454,7 +453,7 @@ def test_boolcontext(self):
self.assertTrue(1j)
def test_conjugate(self):
- self.assertClose(complex(5.3, 9.8).conjugate(), 5.3-9.8j)
+ self.assertEqual(complex(5.3, 9.8).conjugate(), 5.3-9.8j)
def test_constructor(self):
def check(z, x, y):
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