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The following is a simple submission script of a parallel psana batch job run with mpi.  It can be submitted with the command "sbatch submit.sh". The commands specified in the script file will be ran on the first available compute node that fits the resources requested.  There are two ideas: "nodes" and "tasks per node".  A "node" is a physical computer box (with a host-name, for example) but each box/node typically has multiple-cpu-cores.  Typically the tasks-per-node parameter is set to utilize all the cores on each node.

NOTE: when running interactively the "mpirun" command takes a "-n" argument with a number of cores.  However, when running with slurm no "-n" is needed, as slurm infers it from the "--nodes" and "--ntasks-per-node" values.

> cat submit.sh #!/bin/bash

#SBATCH --partition=milano
#SBATCH --nodes=2
#SBATCH --ntasks-per-node=120
#SBATCH --output=%j.log

# -u flushes print statements which can otherwise be hidden if mpi hangs
mpirun python -u -m mpi4py.run my_psana_script.py

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