====== Submit your OpenMPI job with SLURM ======

OpenMPI is built on Magi with SLURM support. To use OpenMPI, you must load the correspondig [[modules|module]]. Feel free to browse the /softs/modules/compiled/gcc/<gcc_version>/openmpi/ to check available versions of OpenMPI. For example :

   nicolas.greneche@magi3:~$ module load /softs/modules/compiled/gcc/10.2.1/openmpi/4.1.2

Then, you can compile your OpenMPI codes :

   nicolas.greneche@magi3:~$ mpicc -o hellompi hellompi.c

The last step is to write a submission script for slurm (here run.slurm) :

   #!/bin/bash
   #SBATCH --job-name=hello
   #SBATCH --output=slurm.out
   #SBATCH --error=slurm.err
   #SBATCH --mail-type=end
   #SBATCH --mail-user=nicolas.greneche@univ-paris13.fr
   #SBATCH --nodes=2
   #SBATCH --ntasks-per-node=2
   
   srun ./hellompi

You can refer to this [[submission_script|documentation]] for more informations on job submission. This run an OpenMPI job on two nodes (--nodes=2) with two tasks per node (--ntasks-per-node=2). it leads to a total of four MPI process (or workers).