[mvapich-discuss] MVAPICH and pthreads

[Pavel Shamis (Pasha)]

In mvapich1 we have CPU/MEMORY support enabled by default and it may 
cause problem for multi thread application. (I had similar problem with 
threaded version of GOTO blas).
The affinity support you may disable with "VIADEV_USE_AFFINITY=0" parameter.

Thanks,
Pasha

Gregory D Abram wrote:
> I have two versions of a MPI program - one which does all the work in one
> thread, and one that spreads the work over several threads, but which does
> all the MPI calls in the original thread.  I've been trying to figure out
> why the threaded version doesn't go any faster on an 8 processor system,
> and found that it appears that all the threads are running on one processor
> (according to the top command - one is pegged, seven are idle).
>
> So I wrote a little test program that spawns 5 threads that just sit there
> doing arithmetic.   When run, top shows 5 processors busy.  I then stuck
> MPI_Init at the start, compiled it for MVAPICH and ran it under mpirun on
> the same node - just one process - and sure enough,  only 1 processor is
> busy.  I then recompiled it for OpenMPI and ran it, again on the same node,
> and got 5 processors busy.
>
> Is this expected?  I'm trying to be MPI-version agnostic, but this is a
> problem.
>
> Greg
>
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>   


-- 
Pavel Shamis (Pasha)
Mellanox Technologies