[MITgcm-support] Parallel performance

[Kevin Oliver]

Hello,

I wonder if anyone can help me with a problem I have regarding running the model in parallel. We 
have just started running MIT model running on a new cluster: Opteron 64 bit Susa 9.1, Sun Grid 
Engine, linux platform, myrinet network (running release 1 patch 8 - this was the version I could 
get to work on an older system). Presumably because not everything is set up optimally, we get 
disappointing performance results running the MIT model in parallel.

The experiment I have done uses a 120x120x40 domain. OLx and OLy are both 3 and all diffusion is 
Laplacian. I've run it with 1x1 and 4x4 subgrids (and several other combinations in between). 
Through-put increases more-or-less monotonically with the number of processers used, but the 4x4 
expriment is only 20% faster than the 1x1 experiment. Delays due to competition in the queue are not 
an issue.

Has looked at how the performance scales with multiple processors on a similar setup, so we know 
what we should be aiming for? Also, is there anything I need to look out for in the code (e.g. 
switches) which could affect performance?

Many thanks for your time,

Kevin

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Dr Kevin Oliver
Senior Research Associate
School of Environmental Sciences
University of East Anglia
Norwich, NR4 7TJ
United Kingdom
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