[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. 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