[slurm-users] ntasks and cpus-per-task

Paul Edmon pedmon at cfa.harvard.edu
Thu Feb 22 09:12:53 MST 2018

Yeah, I've found that in those situations to have people wrap their 
threaded programs in srun inside of sbatch.  That way the scheduler 
knows which process specifically gets the threading.

-Paul Edmon-

On 02/22/2018 10:39 AM, Loris Bennett wrote:
> Hi Paul,
> Paul Edmon <pedmon at cfa.harvard.edu> writes:
>> At least from my experience wonky things can happen with slurm
>> (especially if you have thread affinity on) if you don't rightly
>> divide between -n and -c.  In general I've been telling our users that
>> -c is for threaded applications and -n is for rank based parallelism.
>> This way the thread affinity works out properly.
> Actually we have do an issue with some applications not respecting the
> CPU mask.  I always assumed it was something to do with the way the
> multithreading was programmed in certain applications, but maybe we
> should indeed be getting the users to use multiple CPUs with a single
> task.
> Thanks for the info.
> Cheers,
> Loris

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