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@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@gmail.com> wrote:
HI,
On Wed, May 1, 2013 at 9:09 AM, Yaroslav Halchenko <lists@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 Phone: +1 (603) 646-9834 Fax: +1 (603) 646-1419 WWW: http://www.linkedin.com/in/yarik