without knowing anything about your environment, its reasonable to
suspect that maybe your openmp program is multi-threaded, but slurm is
constraining your job to a single core.  evidence of this should show
up when running top on the node, watching the cpu% used for the
program

On Wed, Apr 23, 2025 at 1:28 PM Jeffrey Layton via slurm-users
<slurm-users@lists.schedmd.com> wrote:
>
> Good morning,
>
> I'm running an NPB test, bt.C that is OpenMP and built using NV HPC SDK (version 25.1). I run it on a compute node by ssh-ing to the node. It runs in about 19.6 seconds.
>
> Then I run the code using a simple job:
>
> Command to submit job: sbatch --nodes=1 run-npb-omp
>
> The script run-npb-omp is the following:
>
> #!/bin/bash
>
> cd /home/.../NPB3.4-OMP/bin
>
> ./bt.C.x
>
>
> When I use Slurm, the job takes 482 seconds.
>
> Nothing really appears in the logs. It doesn't do any IO. No data is copied anywhere. I'm king of at a loss to figure out why. Any suggestions of where to look?
>
> Thanks!
>
> Jeff
>
>
>
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