https://github.com/python/cpython/commit/b6bae536efbec937d6f46f9c98029efa70da3bdb commit: b6bae536efbec937d6f46f9c98029efa70da3bdb branch: main author: Sergey B Kirpichev <[email protected]> committer: vstinner <[email protected]> date: 2026-05-28T13:42:39+02:00 summary:
gh-85989: Add skip_if_double_rounding to test.support (#150219) Co-authored-by: Victor Stinner <[email protected]> files: M Lib/test/support/__init__.py M Lib/test/test_builtin.py M Lib/test/test_math.py M Lib/test/test_statistics.py diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py index 1b4ad5a22ee271..5b0ae098b636ed 100644 --- a/Lib/test/support/__init__.py +++ b/Lib/test/support/__init__.py @@ -73,6 +73,7 @@ "run_no_yield_async_fn", "run_yielding_async_fn", "async_yield", "reset_code", "on_github_actions", "requires_root_user", "requires_non_root_user", + "skip_if_double_rounding", ] @@ -514,6 +515,15 @@ def dec(*args, **kwargs): float.__getformat__("double").startswith("IEEE"), "test requires IEEE 754 doubles") +# detect evidence of double-rounding: +x, y = 1e16, 2.9999 # use temporary values to defeat peephole optimizer +HAVE_DOUBLE_ROUNDING = (x + y == 1e16 + 4) +skip_if_double_rounding = unittest.skipIf(HAVE_DOUBLE_ROUNDING, + "accuracy not guaranteed on " + "machines with double rounding") +del x, y, HAVE_DOUBLE_ROUNDING + + def requires_zlib(reason='requires zlib'): try: import zlib diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py index 1f52b16948c703..1d2c105ac047e1 100644 --- a/Lib/test/test_builtin.py +++ b/Lib/test/test_builtin.py @@ -39,7 +39,7 @@ from test.support.script_helper import assert_python_ok from test.support.testcase import ComplexesAreIdenticalMixin from test.support.warnings_helper import check_warnings -from test.support import requires_IEEE_754 +from test.support import requires_IEEE_754, skip_if_double_rounding from unittest.mock import MagicMock, patch try: import pty, signal @@ -47,11 +47,6 @@ pty = signal = None -# Detect evidence of double-rounding: sum() does not always -# get improved accuracy 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) - # used as proof of globals being used A_GLOBAL_VALUE = 123 A_SENTINEL = sentinel("A_SENTINEL") @@ -2235,8 +2230,7 @@ def __getitem__(self, index): complex(2, -0.0)) @requires_IEEE_754 - @unittest.skipIf(HAVE_DOUBLE_ROUNDING, - "sum accuracy not guaranteed on machines with double rounding") + @skip_if_double_rounding @support.cpython_only # Other implementations may choose a different algorithm def test_sum_accuracy(self): self.assertEqual(sum([0.1] * 10), 1.0) diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py index 7c40f9f94c37ad..85ddf68b3f36ef 100644 --- a/Lib/test/test_math.py +++ b/Lib/test/test_math.py @@ -1,7 +1,8 @@ # Python test set -- math module # XXXX Should not do tests around zero only -from test.support import verbose, requires_IEEE_754 +from test.support import (verbose, requires_IEEE_754, + skip_if_double_rounding) from test import support import unittest import fractions @@ -23,11 +24,6 @@ FLOAT_MAX = sys.float_info.max FLOAT_MIN = sys.float_info.min -# 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] @@ -683,8 +679,7 @@ def testfrexp(name, result, expected): self.assertTrue(math.isnan(math.frexp(NAN)[0])) @requires_IEEE_754 - @unittest.skipIf(HAVE_DOUBLE_ROUNDING, - "fsum is not exact on machines with double rounding") + @skip_if_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 @@ -920,8 +915,7 @@ def testHypot(self): self.assertRaises(TypeError, math.hypot, *([1.0]*18), 'spam') @requires_IEEE_754 - @unittest.skipIf(HAVE_DOUBLE_ROUNDING, - "hypot() loses accuracy on machines with double rounding") + @skip_if_double_rounding @support.skip_on_newlib def testHypotAccuracy(self): # Verify improved accuracy in cases that were known to be inaccurate. @@ -1412,8 +1406,7 @@ def __rmul__(self, other): self.assertEqual(sumprod(*args), 0.0) @requires_IEEE_754 - @unittest.skipIf(HAVE_DOUBLE_ROUNDING, - "sumprod() accuracy not guaranteed on machines with double rounding") + @skip_if_double_rounding @support.cpython_only # Other implementations may choose a different algorithm def test_sumprod_accuracy(self): sumprod = math.sumprod @@ -1498,8 +1491,7 @@ def run(func, *args): ) @requires_IEEE_754 - @unittest.skipIf(HAVE_DOUBLE_ROUNDING, - "sumprod() accuracy not guaranteed on machines with double rounding") + @skip_if_double_rounding @support.cpython_only # Other implementations may choose a different algorithm @support.requires_resource('cpu') def test_sumprod_extended_precision_accuracy(self): diff --git a/Lib/test/test_statistics.py b/Lib/test/test_statistics.py index de7d13651cfea6..700c5ac304f717 100644 --- a/Lib/test/test_statistics.py +++ b/Lib/test/test_statistics.py @@ -16,7 +16,8 @@ import sys import unittest from test import support -from test.support import import_helper, requires_IEEE_754, skip_on_newlib +from test.support import (import_helper, requires_IEEE_754, + skip_if_double_rounding, skip_on_newlib) from decimal import Decimal from fractions import Fraction @@ -28,12 +29,6 @@ # === Helper functions and class === -# Test copied from Lib/test/test_math.py -# 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) - def sign(x): """Return -1.0 for negatives, including -0.0, otherwise +1.0.""" return math.copysign(1, x) @@ -2796,8 +2791,7 @@ def test_sqrtprod_helper_function_fundamentals(self): self.assertEqual(sign(actual), sign(expected)) @requires_IEEE_754 - @unittest.skipIf(HAVE_DOUBLE_ROUNDING, - "accuracy not guaranteed on machines with double rounding") + @skip_if_double_rounding @support.cpython_only # Allow for a weaker sumprod() implementation @skip_on_newlib def test_sqrtprod_helper_function_improved_accuracy(self): _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
