[gmx-developers] mpi and thread command line options

Berk Hess hess at kth.se
Wed Jul 11 10:21:51 CEST 2012

On 07/11/2012 10:10 AM, Roland Schulz wrote:
> On Wed, Jul 11, 2012 at 3:56 AM, Berk Hess <hess at kth.se> wrote:
>> With process MPI we could still use -nt as setting the total number of
>> threads (only
>> meaningful with the Verlet scheme), this would then indirectly control
>> -ntomp.
>> This might not be particularly useful, but at least it makes things
>> consistent.
>> So with process mpi the only option which does nothing is -ntmpi.
> I'm not sure this makes it more consistent. For tMPI "-nt" means the
> total number of threads on that node. For process MPI with "mprun -np
> n" n>1 this isn't true. Thus my suggestion to make "-nt" unavailable
> for process MPI binaries, because I think it might actually be more
> confusing. If we don't remove it I would suggest to have a warning
> "-nt specified with a binary not supporting mpi threads. Assuming you
> mean -ntomp".
> Roland
I meant -nt is total number of threads for the whole simulation (we 
don't mention
node anywhere).
But it's not particularly useful, so we can also disallow the -nt option 
with process MPI.



>> Cheers,
>> Berk
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