benchmarking on Cray XT4

From: Hannes Loeffler (
Date: Tue Mar 16 2010 - 05:50:17 CDT


I am currently running some benchmarks on a Cray XT4 with quad-core
processors. Users can choose how many tasks to run per processor.
What I find is that a single task/processor outperforms a two
task/processor run which itself is faster than a four task/processor
run. I see this behaviour for processor counts from 8 to 2048. Now,
I do understand that there may be performance hits when certain
resource are shared but I would still have expected a different
outcome. Can anyone comment on my findings? Is that the
performance that I have to expect from namd on this architecture?


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