If you are using hydra – the default launcher installed with MPICH, the “-hosts” option accepts a comma separated list, so something like “-hosts node1:4,node2:4,node3:4”. The “:4” tells the launcher to assign 4 processes per host, so you don’t need another “-map-by” option. Alternatively, you could use “-hosts node1,node2,node3 -ppn 4” for the same effect.

 

-- 
Hui Zhou

 

 

From: Jeffrey Layton via discuss <discuss@mpich.org>
Date: Tuesday, October 8, 2024 at 6:50 AM
To: discuss@mpich.org <discuss@mpich.org>
Cc: Jeffrey Layton <laytonjb@gmail.com>
Subject: [mpich-discuss] How to use ppr with mpiexec?

Good morning, I'm trying to "port" an Open MPI script with MPICH and I'm having some trouble. I've got a few questions. What is the form of the "-hosts" option? Is it something like '-hosts node1: 4 node2: 4

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Good morning,

 

I'm trying to "port" an Open MPI script with MPICH and I'm having some trouble. I've got a few questions.

1.  What is the form of the "-hosts" option? Is it something like '-hosts node1:4 node2:4 node3:4 ...'?

2.  The Open MPI script has an option "-map-by ppr:4:node" that tells it to run 4 processes per node and then it runs as many nodes as needed to meet the number of processes. How can I do this in MPICH?

Thanks for the help!

 

Jeff