[slurm-users] Submitting hybrid OpenMPI and OpenMP Jobs

[Paul Edmon]

You might also try swapping to use srun instead of mpiexec as that way 
slurm can give more direction as to what cores have been allocated to 
what. I've found it in the past that mpiexec will ignore what Slurm 
tells it.

-Paul Edmon-

On 9/22/23 8:24 AM, Lambers, Martin wrote:
> Hello,
>
> for this setup it typically helps to disable MPI process binding with 
> "mpirun --bind-to none ..." (or similar) so that OpenMP can use all 
> cores.
>
> Best,
> Martin
>
> On 22/09/2023 13:57, Selch, Brigitte (FIDD) wrote:
>> Hello,
>>
>> one of our applications need hybrid OpenMPI and OpenMP Job-Submit.
>>
>> Only one task is allowed on one node, but this task should use all 
>> cores of the node.
>>
>> So, for example I made:
>>
>> /#!/bin/bash/
>>
>> //
>>
>> /#SBATCH --nodes=5/
>>
>> /#SBATCH --ntasks=5/
>>
>> /#SBATCH --cpus-per-task=44/
>>
>> /#SBATCH --export=ALL/
>>
>> //
>>
>> /export OMP_NUM_THREADS=44/
>>
>> /mpiexec PreonNode test.prscene/
>>
>> But the job does not take more than one  thread:
>>
>> …
>>
>> /Thread binding will be disabled because the full machine is not 
>> available for the process./
>>
>> */Detected 44 CPU threads/*/, 2 l3 caches and 2 packages on the 
>> machine./
>>
>> */Number of CPU processors reported by OpenMP: 1/*
>>
>> */Maximum number of CPU threads reported by OpenMP: 44/*
>>
>> //
>>
>> /Warning: *OMP_NUM_THREADS was set to 44, which is higher than the 
>> number of available processors of *1. Will use 1 threads now./
>>
>> /…/
>>
>> What did I wrong?
>>
>> Does anyone have any idea why OpenMP thinks it can only use one 
>> thread per node?
>>
>> Thanks !
>>
>> Best regards,
>>
>> Brigitte Selch
>>
>> **
>>
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>>
>> IT Produktentwicklung Simulation (FIDD)
>>
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>>
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