[CP2K-user] [CP2K:19379] Help with running cp2k in parallel with Slurm

[Ava Rajh]

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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