[slurm-users] Multiple Program Runs using srun in one Slurm batch Job on one node

Ward Poelmans ward.poelmans at vub.be
Wed Jun 15 15:25:52 UTC 2022

Hi Guillaume,

On 15/06/2022 16:59, Guillaume De Nayer wrote:
> Perhaps I missunderstand the Slurm documentation...
> As thought that the --exclusive option used in combination with sbatch
> will reserve the whole node (40 cores) for the job (submitted with
> sbatch). This part is working fine. I can check it with sacct.
> Then, this job starts subtasks on the reserved 40 cores with srun.
> Therefore I'm using "-n1 -c1" in combination with "srun". I thought that
> it was possible to use the reserved cores inside this job using srun.

You're correct. --exclusive will give you all cores on the nodes but only as much memory as requested.

> The following slightly modified job without --exclusive and with
> --ntasks=2 leads to a similar problem: Only one srun is running at a
> time. The second starts directly after the first one finished.
> #!/bin/bash
> #SBATCH --job-name=test_multi_prog_srun
> #SBATCH --ntasks=2
> #SBATCH --partition=short
> #SBATCH --time=02:00:00
> srun -vvv --exact -n1 -c1 sleep 20 > srun1.log 2>&1 &
> srun -vvv --exact -n1 -c1 sleep 30 > srun2.log 2>&1 &
> wait

This should work... It works on our cluster. Are you sure they don't run in parallel?

We usually recommend to use gnu parallel or xargs like:

xargs -P $SLURM_NTASKS srun -N 1 -n 1 -c 1 --exact sleep 30

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