diff options
| -rw-r--r-- | Lib/test/test_math.py | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py index 9e646ac..d74f01f 100644 --- a/Lib/test/test_math.py +++ b/Lib/test/test_math.py @@ -13,6 +13,11 @@ NAN = float('nan') INF = float('inf') NINF = float('-inf') +# detect evidence of double-rounding: fsum is not always correctly +# rounded on machines that suffer from double rounding. +x, y = 1e16, 2.9999 # use temporary values to defeat peephole optimizer +HAVE_DOUBLE_ROUNDING = (x + y == 1e16 + 4) + # locate file with test values if __name__ == '__main__': file = sys.argv[0] @@ -359,6 +364,10 @@ class MathTests(unittest.TestCase): self.assertEquals(math.frexp(NINF)[0], NINF) self.assert_(math.isnan(math.frexp(NAN)[0])) + @unittest.skipUnless(float.__getformat__("double").startswith("IEEE"), + "test requires IEEE 754 doubles") + @unittest.skipIf(HAVE_DOUBLE_ROUNDING, + "fsum is not exact on machines with double rounding") def testFsum(self): # math.fsum relies on exact rounding for correct operation. # There's a known problem with IA32 floating-point that causes @@ -368,14 +377,6 @@ class MathTests(unittest.TestCase): # 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+2.0 != 1e16+2.9999: - return - # Python version of math.fsum, for comparison. Uses a # different algorithm based on frexp, ldexp and integer # arithmetic. |