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srun

srun is the SLURM command used to launch tasks within a job allocation. It can be used in both batch scripts and on the command line to:

Start one or more job ‘steps’ in a batch job (a step can request and use some or all of the resources allocated to the job; steps can run sequentially or in parallel)
- useful for analysing performance across multiple stages of a workflow
Launch MPI or multi-task jobs
- (e.g. with --ntasks > 1)
- where multiple processes need to be started across CPUs or nodes
Run an interactive job
- for example, srun --pty bash -i

Documentation

Run man srun on the system for full details.

To launch an interactive shell:

srun --pty bash -i

To run a non-interactive job directly:

srun --export=ALL --time=00:10:00 --mem=1G python3 my_script.py 100000000

In a batch script:

#SBATCH --ntasks=4
srun --export=ALL ./my_parallel_app

For simple, single-task jobs, srun is optional in batch scripts — your command can be run directly.