[Beowulf] Thought that this might be of interest
landman at scalableinformatics.com
Mon Nov 6 11:33:35 EST 2006
Jeffrey B. Layton wrote:
> So which one is faster - Woodcrest or Opteron - really
> depends on your code.
Most of the testing I have done, where Woodcrest is faster appears to be
linked to the cache size. Since I used the PGI compilers, and built a
single binary (not the mixed binary), it sort of pulls this out and
A CPU with 4M apparent cache for a single processor will run circles
around a machine with a 1M apparent cache per processor for cache
friendly apps running a single thread. As you increase the number of
threads per socket, things even out. And this jives well with my
testing to date.
That said, I am quite interested in trying to feed the Woodcrest SSE
pipeline at a better rate than the compilers allow for (same with the
Opteron). Unfortunately this gets into the area of hand coded SSE*, and
the Intel compiler does a decent job supporting this (while the PGI
doesn't). Since the Intel compiler has other things working against it
(ahem!), this makes the job of writing fast code somewhat harder.
I know, lets all just use GCC ...
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 : +1 734 786 8452 or +1 866 888 3112
cell : +1 734 612 4615
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