[CIG-MC] Citcom runtime on Lonestar vs Ranger (Teragrid): Insights/experience?

[Erin Burkett]

Hi all,
For those of you who have experience running versions of Citcom on the
Teragrid (specifically Lonestar and Ranger), I am seeking some
insight/advice to help understand and minimize/eliminate (if possible) the
longer runtimes I'm currently encountering on Ranger (vs. Lonestar).

I'm attaching a table summarizing timing results of a small test I've run
using various combinations of the different compilers, compiler options,
mpicc versions.  This follows an earlier run on 480 processors resulting in
a 20% longer runtime on Ranger vs Lonestar that first caused me to be aware
of the difference.

I have gathered that because Lonestar has 4 cores/machine and Ranger has 16
cores/machine, the interconnect speed (Citcom uses interconnect heavily/is
communications intensive?) may be limiting the speed despite Ranger being
more powerful.

I would appreciate any shared experience, suggestions, or insights you may
have to help identify the best machine and specifications to use for running
Citcom.
Thank you!
Erin

-- 
~~~~~~~~~~~~~~~~~~~~~
Erin R. Burkett
University of California, Davis
2205 Earth and Physical Sciences
Davis, CA 95616

http://mygeologypage.ucdavis.edu/burkett/
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