[Beowulf] CCL:Question regarding Mac G5 performance

Konstantin Kudin konstantin_kudin at yahoo.com
Mon May 24 15:10:43 PDT 2004

--- Joe Landman <landman at scalableinformatics.com> wrote:

> >  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.  

 Well, bioinformatics codes presumably run mostly integer operations.
This is very different from heavy floating point calculations in G03
which are double precision in all architectures and run with
approximately the same speed regardless of 32/64 bitness.
> 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.

 With G03, some types of jobs will mostly be compute bound, and others
will be mostly I/O bound. This is reasonably trivial to predict
beforehand. I've tested jobs which were compute bound because testing
the other side of the equation is more difficult due to more factors.

 For I/O bound jobs a box with loads of RAM and fast sequential I/O is
the best. Something like dual-quad Opteron with 16-32Gb of RAM and 2-4
ATA disks with RAID0 (striping) is a good choice these days.


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