[CP2K-user] [CP2K:19384] Help with running cp2k in parallel with Slurm

[Krack Matthias]

Hi Ava

Do you run the “srun” command as part of a SLURM batch job file with a #SBATCH header section or interactively?
Your guess is right, the –ntasks flag defines the number of MPI ranks.

Best

Matthias

From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Ava Rajh <ava.rajh at gmail.com>
Date: Wednesday, 18 October 2023 at 14:17
To: cp2k <cp2k at googlegroups.com>
Subject: [CP2K:19379] Help with running cp2k in parallel with Slurm
Dear all,

I am trying to run cp2k on our HPC cluster and I am new in doing any kind of parallel computing and work on a cluster, so I would appreciate if some help and I apologize if I am missing something obvious.
I am trying to use Cp2k in combination with apptainer  and I followed instructions at https://github.com/cp2k/cp2k/tree/master/tools/apptainer

I have a .sif file in my work directory and if I work within it (Running MPI within the container), everything works perfectly and I can set the number of MPI threads.

But when trying to run it through slurm, I can't seem to be able to set the number of MPI processes per node. If i start a command like:
srun --ntasks=2 apptainer run -B $PWD cp2k-2023.2_mpich_generic_psmp.sif cp2k -i H2O-32.in
it just starts 2 instances of the program that run at the same time, and for each, the total number of message passing processes is 1. I am able to set and change the number of OpenMP threads though.
So my question would be first, am I wrongly assuming that --ntasks X should correspond to the number of MPI threads? And if I am, how would I set it.

Please let me know if I need to provide any more information to diagnose the issue.
Thank you very much for the help and kind regards,
Ava Rajh
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