[gmx-users] specifying rank using mpich w/ Dual G4 Mac Cluster

David spoel at xray.bmc.uu.se
Fri Dec 20 18:49:58 CET 2002

On Fri, 2002-12-20 at 19:21, DaJustice1 at aol.com wrote:
> Hello all,
> I am trying to use MPICH with a cluster of Dual G4 Macs , and I run into performace problems.  I have found that when running mpi with 1 process on the originating computer and 2 processes on 1 other computer with 2 processors the performace is good (specifying 3 nodes -np 3).  But when I add in another dual G4 and specify 5 nodes (-np 5), mpi wants to put 2 processes on the originating computer, 2 on the second, and 1 on the third.  This causes horrible performace.  I have tried to specify 1 processor for the originating computer in the machines file, but mpi still will put two processes on that computer.  Is there any way that I can specify the rank, and the number of processes that will be run on each computer?  Possibly with -map or some other flag, or is there a better solution possibly with Lam??? 
with lam you can specify it exactly as you want it.

> Thank you ahead of time,
> ~Justice~
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Groeten, David.
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://xray.bmc.uu.se/~spoel

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