[Numpy-discussion] could anyone check on a 32bit system?
robert.kern at gmail.com
Wed May 1 14:07:14 EDT 2013
On Wed, May 1, 2013 at 6:24 PM, Matthew Brett <matthew.brett at gmail.com> wrote:
> 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.
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