[gmx-developers] max cpu scale-up
roland at utk.edu
Sat Sep 20 02:35:11 CEST 2008
On Fri, Sep 19, 2008 at 1:31 PM, <hessb at mpip-mainz.mpg.de> wrote:
> > What -ddorder cartesian does?
> This determines the order of the PP and PME nodes.
> If the XT4 would really support cartesian communication this would
> be a lot faster, but unfortunately it does not.
> Still it will probably be faster when all the PME nodes are physically
> close toghether. -ddorder cartesian will do this.
> -ddorder pp_pme will also work well, but I expect cartesian
> to be slightly faster, you can try both.
For one of my test systems interleave is fastest on XT4. But the difference
is very small (5%). My system with 120k atoms scales to 160 cores (with 48
cores for PME) giving 21.1ns/day. XT4 latency is really high. So that in
some cases it is 50% slower than on low latency clusters (Myri 10G).
ORNL/UT Center for Molecular Biophysics cmb.ornl.gov
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