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Author vstinner
Recipients jcea, mark.dickinson, python-dev, rhettinger, vstinner
Date 2011-05-09.12:10:12
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Message-id <1304943013.84.0.527719124859.issue11888@psf.upfronthosting.co.za>
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Content 
Issue #11888: Use system log2() when available
http://hg.python.org/cpython/rev/565f43f6bed4

"I expect the system libc to use more accurate functions than Python."

You know what? Mac OS X log2 is less accurate than Python log2! A log2 test failed on "x86 Tiger 3.x":

http://www.python.org/dev/buildbot/all/builders/x86%20Tiger%203.x/builds/2488
======================================================================
FAIL: testLog2 (test.test_math.MathTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/db3l/buildarea/3.x.bolen-tiger/build/Lib/test/test_math.py", line 658, in testLog2
    self.assertEqual(actual, expected)
AssertionError: Lists differ: [-324.0, -323.0, -322.0, -321.... != [-324.0, -323.0, -322.0, -321....

First differing element 69:
-254.99999999999997
-255.0
----------------------------------------------------------------------

Should I revert my patch or should we test the system log2 in configure to check if it is as accurate or more accurate than Mark's algorithm?
History
Date User Action Args
2011-05-09 12:10:13vstinnersetrecipients: + vstinner, rhettinger, jcea, mark.dickinson, python-dev
2011-05-09 12:10:13vstinnersetmessageid: <1304943013.84.0.527719124859.issue11888@psf.upfronthosting.co.za>
2011-05-09 12:10:13vstinnerlinkissue11888 messages
2011-05-09 12:10:12vstinnercreate