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

DaJustice1 at aol.com DaJustice1 at aol.com
Fri Dec 20 19:21:21 CET 2002

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??? 

Thank you ahead of time,

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