[MPICH] MPI_Comm_spawn and hosts

Rajeev Thakur thakur at mcs.anl.gov
Mon Aug 27 16:50:29 CDT 2007

By default, spawn probably launches the processes in the same way as mpiexec
and hence they land on the same nodes. (This should probably be changed.) To
launch processes on specific nodes, you can use an info object with the key
"host" set to the hostname (as defined in the MPI spec). This has to be done
separately for each process, so you have to use MPI_Comm_spawn_multiple.
This might be difficult to do when you use PBS because you don't know the
names of the hosts before hand.


> -----Original Message-----
> From: owner-mpich-discuss at mcs.anl.gov 
> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Wei-keng Liao
> Sent: Friday, August 24, 2007 2:15 PM
> To: mpich-discuss at mcs.anl.gov
> Subject: [MPICH] MPI_Comm_spawn and hosts
> I have a simple program that calls MPI_Comm_spawn() to spawn 
> a group of 
> MPI processes. I found that the hosts running parent and 
> child groups are 
> overlapped. I ran The job ran though PBS with enough compute nodes 
> allocated for parents and children to be disjoint.
> How do I ensure the hosts running parents and children are 
> not overlapped?
> Wei-keng

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