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Skip math.sum tests on non IEEE 754 platforms, and on IEEE 754 platforms

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that exhibit the problem described in issue #2937.
This commit is contained in:
Mark Dickinson 2008-05-23 12:07:36 +00:00
parent 2d593cc679
commit badd7da622
1 changed files with 16 additions and 0 deletions
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16
Lib/test/test_math.py
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@ -631,6 +631,22 @@ class MathTests(unittest.TestCase):
self.assert_(math.isnan(math.sqrt(NAN)))
def testSum(self):
# math.sum relies on exact rounding for correct operation.
# There's a known problem with IA32 floating-point that causes
# inexact rounding in some situations, and will cause the
# math.sum tests below to fail; see issue #2937. On non IEEE
# 754 platforms, and on IEEE 754 platforms that exhibit the
# problem described in issue #2937, we simply skip the whole
# test.
if not float.__getformat__("double").startswith("IEEE"):
return
# on IEEE 754 compliant machines, both of the expressions
# below should round to 10000000000000002.0.
if 1e16+2.999 != 1e16+2.9999:
return
# Python version of math.sum algorithm, for comparison
def msum(iterable):
"""Full precision sum of values in iterable. Returns the value of