Do I need a single bash file for each task in SLURM? - bash

Question

I am trying to launch several task in a SLURM-managed cluster, and would like to avoid dealing with dozens of files.
Right now, I have 50 tasks (subscripted i, and for simplicity, i is also the input parameter of my program), and for each one a single bash file slurm_run_i.sh which indicates the computations configuration, and the srun command:
#!/bin/bash
#SBATCH --ntasks=1
#SBATCH --cpus-per-task=1
#SBATCH -J pltCV
#SBATCH --mem=30G
srun python plotConvergence.py i
I am then using another bash file to submit all these tasks, slurm_run_all.sh
#!/bin/bash
for i in {1..50}:
sbatch slurm_run_$i.sh
done
This works (50 jobs are running on the cluster), but I find it troublesome to have more than 50 input files. Searching a solution, I came up with the & command, obtaining something as:
#!/bin/bash
#SBATCH --ntasks=50
#SBATCH --cpus-per-task=1
#SBATCH -J pltall
#SBATCH --mem=30G
# Running jobs
srun python plotConvergence.py 1 &
srun python plotConvergence.py 2 &
...
srun python plotConvergence.py 49 &
srun python plotConvergence.py 50 &
wait
echo "All done"
Which seems to run as well. However, I cannot manage each of these jobs independently: the output of squeue shows I have a single job (pltall) running on a single node. As there are only 12 cores on each node in the partition I am working in, I am assuming most of my jobs are waiting on the single node I've been allocated to. Setting the -N option doesn't change anything too.. Moreover, I cannot cancel some jobs individually anymore if I realize there's a mistake or something, which sounds problematic to me.
Is my interpretation right, and is there a better way (I guess) than my attempt to process several jobs in slurm without being lost among many files ?

Answer 1

What you are looking for is the jobs array feature of Slurm.
In your case, you would have a single submission file (slurm_run.sh) like this:
#!/bin/bash
#SBATCH --ntasks=1
#SBATCH --cpus-per-task=1
#SBATCH -J pltCV
#SBATCH --mem=30G
#SBATCH --array=1-50
srun python plotConvergence.py ${SLURM_ARRAY_TASK_ID}
and then submit the array of jobs with
sbatch slurm_run.sh
You will see that you will have 50 jobs submitted. You can cancel all of them at once or one by one. See the man page of sbatch for details.