[slurm-users] requesting resources and afterwards launch an array of calculations

[Mark Hahn]

> Literal job arrays are built into Slurm: https://slurm.schedmd.com/job_array.html

yes, and the best way to describe these are "job generators".
that is, you submit one and it sits in the pending queue, while 
the array elements kind of "bud" off the parent job.  each of 
the array jobs is a full-fledged job (full-cost, all the accounting
and setup/teardown overhead, just not submission overhead or stuffing
the pending queue.)

I don't think this is what the OP is looking for.

> Alternatively, if you wanted to allocate a set of CPUs for a parallel task, and then run a set of single-CPU tasks in the same job, something like:
>
>  #!/bin/bash
>  #SBATCH --ntasks=30
>  srun --ntasks=${SLURM_NTASKS} hostname

I think this is *exactly* what the OP is looking for!  this runs each 
element of work as a step within a single allocation.  you get some 
accounting, but are not bothering the scheduler during the job.

an alternative would be to run something like GNU Parallel within the job.

regards, mark hahn.
-- 
operator may differ from spokesperson.	            hahn at mcmaster.ca