mpiexec problem.

[Chris Samuel]

On Thu, 21 Jun 2007, Steve Young wrote:

> The osc mpiexec spawns 8 seperate processes while mpirun does them in
> parallel. Any ideas what I could try to remedy this? Thanks,

If you are not using Myrinet (and have not altered the build time default) 
then you will need to specify the correct MPICH communication lib to use.

Quoting the manual page:

       -comm type
             Specify  the  communication  library used by your code.  Each MPI
             library has different mechanisms for starting all  the  processes
             of a parallel job, thus you must specify to mpiexec which library
             you use so that it can set up the environment  of  the  processes
             correctly.   The  argument type must be one of:  mpich-gm, mpich-
             mx, mpich-p4, mpich-ib, mpich-rai, mpich2-pmi, lam,  shmem,  emp,
             none;  although  the code may not have been compiled with support
             for some of those.  If this argument is  not  specified,  mpiexec
             will  look  for the environment variable MPIEXEC_COMM which could
             specify one of those arguments.  If this fails,  the  compiled-in
             default communication library is chosen.

What you see is often diagnostic of someone using the default MPICH-GM support 
for a P4 application.

cheers,
Chris
-- 
 Christopher Samuel - (03)9925 4751 - VPAC Deputy Systems Manager
 Victorian Partnership for Advanced Computing http://www.vpac.org/
 Bldg 91, 110 Victoria Street, Carlton South, VIC 3053, Australia

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