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Eclips4 opened this issue Oct 31, 2024 · 7 comments
Closed

test_math fails on Windows #126252

Eclips4 opened this issue Oct 31, 2024 · 7 comments
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OS-windows stdlib Python modules in the Lib dir tests Tests in the Lib/test dir type-bug An unexpected behavior, bug, or error

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@Eclips4
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Eclips4 commented Oct 31, 2024 •
edited by github-actions bot
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Bug report

Bug description:

./python -m test -v test_math
======================================================================
ERROR: test_fma_overflow (test.test_math.FMATests.test_fma_overflow)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\eclips4\programming\cpython\Lib\test\test_math.py", line 2801, in test_fma_overflow
    self.assertEqual(math.fma(a, b, -c),
                     ~~~~~~~~^^^^^^^^^^
OverflowError: overflow in fma

======================================================================
FAIL: test_fma_zero_result (test.test_math.FMATests.test_fma_zero_result)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\eclips4\programming\cpython\Lib\test\test_math.py", line 2760, in test_fma_zero_result
    self.assertIsNegativeZero(math.fma(tiny, -tiny, 0.0))
    ~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\eclips4\programming\cpython\Lib\test\test_math.py", line 2876, in assertIsNegativeZero
    self.assertTrue(
    ~~~~~~~~~~~~~~~^
        value == 0 and math.copysign(1, value) < 0,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        msg="Expected a negative zero, got {!r}".format(value)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
AssertionError: False is not true : Expected a negative zero, got 0.0

======================================================================
FAIL: test_random (test.test_math.FMATests.test_random)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\eclips4\programming\cpython\Lib\test\test_math.py", line 2859, in test_random
    self.assertEqual(math.fma(a, b, c), expected)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 0.5506672157701096 != 0.5506672157701097

----------------------------------------------------------------------
Ran 87 tests in 14.275s

FAILED (failures=2, errors=1, skipped=2)
test test_math failed
test_math failed (1 error, 2 failures)

== Tests result: FAILURE ==

1 test failed:
    test_math

Total duration: 16.3 sec
Total tests: run=87 failures=2 skipped=2
Total test files: run=1/1 failed=1
Result: FAILURE

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows
@Eclips4 Eclips4 added type-bug An unexpected behavior, bug, or error tests Tests in the Lib/test dir OS-windows labels Oct 31, 2024
@terryjreedy
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For me, on current Windows 10, with fresh "Python 3.14.0a1+ experimental free-threading build (heads/main-dirty:0e8665554b2, Oct 31 2024, 14:58:59) [MSC v.1941 64 bit (AMD64)] on win32", 87 tests pass in 10 sec. With installed python.org "Python 3.14.0a1 (tags/v3.14.0a1:8cdaca8, Oct 15 2024, 20:08:21)", ditto, in 1 sec.

@terryjreedy terryjreedy added the stdlib Python modules in the Lib dir label Oct 31, 2024
@eendebakpt
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eendebakpt commented Oct 31, 2024 •
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Tested with main (commit dd3c0fa, Python 3.14.0a1+ (heads/main:dd3c0fa3fd2, Oct 31 2024, 21:48:53) [MSC v.1939 64 bit (AMD64)] on win32) and a normal Windows build, but I cannot reproduce this one either.

@tim-one
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tim-one commented Oct 31, 2024

Please show the first line displayed when you open an interactive shell. For example, with the released Python 3.13,.0 on 64-bit Windows from python.org:

$ python
Python 3.13.0 (tags/v3.13.0:60403a5, Oct  7 2024, 09:38:07) [MSC v.1941 64 bit (AMD64)] on win32

@Eclips4
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Eclips4 commented Nov 1, 2024

Please show the first line displayed when you open an interactive shell. For example, with the released Python 3.13,.0 on 64-bit Windows from python.org:

$ python
Python 3.13.0 (tags/v3.13.0:60403a5, Oct  7 2024, 09:38:07) [MSC v.1941 64 bit (AMD64)] on win32

Python 3.14.0a1+ (heads/main:0e8665554b2, Oct 31 2024, 18:03:04) [MSC v.1941 64 bit (AMD64)] on win32

@clairvoyante
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https://developercommunity.visualstudio.com/t/MSVCs-fma-implementation-is-incorrect-o/10594003 ?

@zooba
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zooba commented Nov 4, 2024

Given the linked issue, this will be solved by an OS update that we can't control and don't need to do anything about.

Unless someone wants to add a platform-specific tolerance to the test so that the failure goes away (without losing bigger failures such as it starting to return zero), there's no need to keep this open.

@Eclips4 Eclips4 closed this as not planned Won't fix, can't repro, duplicate, stale Nov 4, 2024
@clairvoyante
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Or use math.sumprod() instead, like #100485 (comment) :

def fma(x, y, z):
    'Return x * y + z with a single rounding'
    return sumprod((x, z), (y, 1.0))

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@eendebakpt @zooba @tim-one @terryjreedy @clairvoyante @Eclips4