[Numpy-discussion] could anyone check on a 32bit system?

[Yaroslav Halchenko]

just for completeness... I haven't yet double checked if I have done it
correctly but here is the bisected commit:

aed9925a9d5fe9a407d0ca2c65cb577116c4d0f1 is the first bad commit
commit aed9925a9d5fe9a407d0ca2c65cb577116c4d0f1
Author: Mark Wiebe <mwiebe at enthought.com>
Date:   Tue Aug 2 13:34:13 2011 -0500

    ENH: ufunc: Rewrite PyUFunc_Reduce to be more general and easier to adapt to NA masks
    
    This generalizes the 'axis' parameter to accept None or a list of
    axes on which to do the reduction.

:040000 040000 2bdd71a1ea60c0dbfe370c77f69724fab28038e1 44f54a15f480ccaf519d10e9c42032de86bd0dca M      numpy
bisect run success

FWIW ( ;-) ):

# git describe --tags aed9925a9d5fe9a407d0ca2c65cb577116c4d0f1
v0.3.0-7757-gaed9925

# git describe --tags --contains aed9925a9d5fe9a407d0ca2c65cb577116c4d0f1
v1.7.0b1~377^2~126


On Wed, 01 May 2013, Robert Kern wrote:

> On Wed, May 1, 2013 at 6:24 PM, Matthew Brett <matthew.brett at gmail.com> wrote:
> > HI,

> > On Wed, May 1, 2013 at 9:09 AM, Yaroslav Halchenko <lists at onerussian.com> wrote:

> >> 3. they are identical on other architectures (e.g. amd64)

> > To me that is surprising.  I would have guessed that the order is the
> > same on 32 and 64 bit, but something about the precision of
> > intermediate operations is different.   I don't know enough about
> > amd64 to guess what that could be.  Bradley's suggestion seems kind of
> > reasonable but it's strange that numpy should use intel-80 bit
> > intermediate values differently for 32 and 64 bit.

> "numpy" isn't doing anything different between the two. numpy
> generates the same C code. The C compiler may be generating different
> machine instructions for that code on different architectures, even
> closely related ones like i386 and amd64. Different optimization flags
> and compiler versions will probably also affect this, not just the
> target architecture. It's possible that those are actually the source
> of this observation.
-- 
Yaroslav O. Halchenko, Ph.D.
http://neuro.debian.net http://www.pymvpa.org http://www.fail2ban.org
Senior Research Associate,     Psychological and Brain Sciences Dept.
Dartmouth College, 419 Moore Hall, Hinman Box 6207, Hanover, NH 03755
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