[OMPI users] Help with binding processes correctly in Hybrid code (Openmpi +openmp)

[Anil K. Dasanna]

Hello all,

I am relatively new to mpi computing. I am doing particle simulations.
So far, I only used pure mpi and I never had a problem. But for my system,
its the best if one uses hybrid programming.
But I always fail to correctly bind all processes and receive binding
errors from cluster.
Could one of you please clarify correct parameters for mpirun for below two
cases:

1) I would like to use lets say two mpi tasks and 16 processors as openmp
threads.
I request nodes:2:ppn=16.
2) For the same case, how should i give parameters such that i have 4 mpi
tasks and
8 openmp threads.

I also tried options with --map-by and it happened that sometimes both mpi
tasks are being selected
from same node and other node is idle. I really appreciate your help.
And my openmp version is 1.8.

[Gilles Gouaillardet]

Hi,

per https://www2.cisl.ucar.edu/resources/computational-systems/cheyenne/running-jobs/pbs-pro-job-script-examples,
you can try

#PBS -l select=2:ncpus=16:mpiprocs=2:ompthreads=8

Cheers,

Gilles


On Tue, Nov 14, 2017 at 4:32 PM, Anil K. Dasanna

Post by Anil K. Dasanna
Hello all,
I am relatively new to mpi computing. I am doing particle simulations.
So far, I only used pure mpi and I never had a problem. But for my system,
its the best if one uses hybrid programming.
But I always fail to correctly bind all processes and receive binding errors
from cluster.
Could one of you please clarify correct parameters for mpirun for below two
1) I would like to use lets say two mpi tasks and 16 processors as openmp
threads.
I request nodes:2:ppn=16.
2) For the same case, how should i give parameters such that i have 4 mpi
tasks and
8 openmp threads.
I also tried options with --map-by and it happened that sometimes both mpi
tasks are being selected
from same node and other node is idle. I really appreciate your help.
And my openmp version is 1.8.
--
Kind Regards,
Anil.
*********
"Its impossible" - said Pride
"Its risky" - said Experience
"Its pointless" - said Reason
"Give it a try" - whispered the heart
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