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Strange behavior of ldexp on Python2.5 + Wine (Trac #1641) #2237

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numpy-gitbot opened this issue Oct 19, 2012 · 1 comment
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Strange behavior of ldexp on Python2.5 + Wine (Trac #1641) #2237

numpy-gitbot opened this issue Oct 19, 2012 · 1 comment
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00 - Bug component: numpy._core
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1.5.1

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Original ticket http://projects.scipy.org/numpy/ticket/1641 on 2010-10-19 by @pv, assigned to unknown.

On Python 2.5 + MinGW + Wine (and probably on a real Windows, too):

>>> import numpy as np
>>> np.iinfo('l').max
2147483647
>>> np.ldexp(2, 2147483647)
0.0
>>> np.ldexp(2, 2147483646)
0.0
>>> np.ldexp(2, 2147483645)
Warning: overflow encountered in ldexp
inf

On Python 2.6 the above works correctly.

This occurs also on d24db3430a and is therefore independent of #2229.
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@pv wrote on 2010-10-19

Ok, got WineDBG working (see http://www.winehq.org/pipermail/wine-devel/2010-July/084788.html for an important hint).

The reason seems to be that python.org 2.5 binary is linked with a C runtime that has a broken implementation of ldexp (oh joy), and this is also what Numpy gets. This is easily tested by inserting printf("\n>>>%g<<<<\n", ldexp(2.0, 2147483647)); in e.g. multiarraymodule.c:initmultiarray.

We cannot fix this, as it's not our bug. The test should just be marked as KNOWNFAIL on Python < 2.5 on Windows. Marked so in 3747ab5 and c6504f5

@numpy-gitbot numpy-gitbot mentioned this issue Oct 23, 2012
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