[Beowulf] Strange Opteron 2350 performance: Gaussian-03
landman at scalableinformatics.com
Sat Jun 28 14:48:02 EDT 2008
Mikhail Kuzminsky wrote:
> And the question is - may be that OLD binary (w/o recompilation) will
> run so slow on Opteron 2350 core ?
This is possible, depending upon the compiler used. Though I have to
admit that I find it odd that it would be the case within the Opteron
family and not between Opteron and Xeon.
Intel compilers used to (haven't checked 10.1) switch between fast
(SSE*) and slow (x87 FP) paths as a function of a processor version
string. If this is an old Intel compiler built code, this is possible
that the code paths may be different, though as noted, I would find that
surprising if this were the case within the Opteron family.
Modern PGI compilers (suggested default for Gaussian-03 last I
checked) have the ability to do this as well, though I don't know how
they implement it (capability testing hopefully?)
Out of curiousity, how does streams run on both systems? Also, it is
possible, with a larger cache, that you might be running into some odd
cache effects (tlb/page thrashing). But DFTs are usually "small" and
thus "sensitive" to cache size.
You might be able to instrument the run within a papi wrapper, and
see if you observe a large number of cache/tlb flushes for some reason.
On a related note: are you using a stepping before B3 of 2350? That
could impact performance, if you have the patch in place or have the
tlb/cache turned off in bios (some MB makers created a patch to do this).
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web : http://www.scalableinformatics.com
phone: +1 734 786 8423
fax : +1 866 888 3112
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