Dear Stefan,

I could not spot an error in the slurm or python script.

As Sandra already pointed out, it is advantageous to export some OMP variable in your jobfile.
Besides OMP_NUM_THREADS, it is also good to set

• export OMP_PROC_BIND=TRUE  -> pins the threads to certain cores, increases NEST performance
• export OMP_DISPLAY_ENV=TRUE -> gives information on whether OMP was set up correctly
  
• export OMP_DISPLAY_AFFINITY=TRUE -> gives information on whether OMP was set up correctly

See also here for the part of the NEST documentation regarding parallel computing, generally a good source of information.

Regarding your concrete problem, it is somewhat difficult to debug with the information available

What would help is the standard error generated by slurm when exporting the two OMP variables regarding the OMP configuration, i.e. OMP_DISPLAY_ENV=TRUE and OMP_DISPLAY_AFFINITY=TRUE

Best

Anno

Dear Sandra, 

I have done all of what you describe, and still only one OpenMP thread is being used on each node. (I set all above listed variables to 16 threads)

For reproducibility: I attach my SLURM batch script and the simulation script. I use NEST 3.4 compiled with openmp and mpi, and Intel(R) MPI Library for Linux* OS, Version 2019 Update 12 Build 20210429 (id: e380127cb).

Best regards,

On Sun, 6 Aug 2023 at 12:02, Sandra Diaz <s.diaz@fz-juelich.de> wrote:

Dear Stefan,

Have you tried setting the OMP variable in your batch script? Something like:

export OMP_NUM_THREADS=<No. of threads>

You should do this before your srun call to the nest script and in combination to setting the local_num_threads, as well as the right value for -c (or --cpus-per-task).

All the best,
Sandra

On 05.08.23 13:05, Stefan Dvoretskii wrote:

Hello all, 

I am trying to use as much parallelism as possible on my computing grid. In this sense, I combine MPI+OpenMP. MPI processes are spawned fine, but OpenMP threads always amount to 1, no matter that I set local_num_threads correctly (https://nest-simulator.readthedocs.io/en/latest/hpc/slurm_script.html#set-local-num-threads-in-your-nest-script) as well as all SLURM variables. I am sure I have compiled nest with OpenMP too.

I use slightly modified izhikevich neurons with stdp synapses. Can the model specifics be the cause of underutilizing available threads? Or is there something else in the system that could be the reason for that?

Best regards,

--

Stefan Dvoretskii

_______________________________________________
NEST Users mailing list -- users@nest-simulator.org
To unsubscribe send an email to users-leave@nest-simulator.org

-- 
Dr. Sandra Diaz Pier
Simulation & Data Lab Neuroscience
Jülich Supercomputing Centre
Institute for Advanced Simulation
Forschungszentrum Jülich

Office: +49 2461 61-8913

---------------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------------
Forschungszentrum Juelich GmbH
52425 Juelich
Sitz der Gesellschaft: Juelich
Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498
Vorsitzender des Aufsichtsrats: MinDir Stefan Müller
Geschaeftsfuehrung: Prof. Dr.-Ing. Wolfgang Marquardt (Vorsitzender),
Karsten Beneke (stellv. Vorsitzender), Dr. Ir. Pieter Jansens,
Prof. Dr. Astrid Lambrecht, Prof. Dr. Frauke Melchior
---------------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------------

--

Stefan Dvoretskii

_______________________________________________
NEST Users mailing list -- users@nest-simulator.org
To unsubscribe send an email to users-leave@nest-simulator.org