[Beowulf] CCL:Question regarding Mac G5 performance

[Joe Landman]

On Mon, 24 May 2004 10:45:32 -0700 (PDT), Konstantin Kudin wrote

[...]

> > I would be curious to see the performance with a 64 bit compilation
> > running under a 64 bit OS (SuSE 9.x)
> 
>  Me too :-) According to this CCL message (and other reliable sources),
> the official 64-bit support is just around the corner:
> 
> http://www.ccl.net/cgi-bin/ccl/message.cgi?2004+04+28+013
> (see reply #2)
> 
>  It is unlikely that one can gain much speed from going to 64 bits, but
> the support for larger memory and unlimited scratch files is very
> worthwhile in itself.

I have seen in md43, moldy, and a few others, about 20-30% under gcc
recompilation with -m64 on Opteron.  For informatics codes it was about the same.  

Your mileage will vary of course, but I expect with Gaussian and others that
overflow memory, the overall system design will be as important (if not more so)
to the overall performance than the CPU architecture, unless you can somehow
isolate the computation to never spill to disk.



--
Joseph Landman, Ph.D
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web  : http://scalableinformatics.com
phone: +1 734 612 4615