Dear Shri, Just tried with --download-mpich and all is well. Thanks.
Confirmed that using --download-openmpi (instead of using Ubuntu's OpenMPI) produces the same slowdown in communications. Another visible symptom is that it takes a long time to print the log_summary data. Any hints as to why OpenMPI displays this behavior. Thank you again for your help. Regards, Gon?alo On Thu, Feb 14, 2013 at 5:32 PM, Shri <abhyshr at mcs.anl.gov> wrote: > This has something to do with OpenMPI. I cannot reproduce this issue with > MPICH. Can you try switching to MPICH (--download-mpich). > > Shri > On Feb 14, 2013, at 6:58 AM, Gon?alo Albuquerque wrote: > > > Dear All, > > > > I'm experimenting with PETSc hybrid MPI/OpenMP capabilities and I have > run a rather simple test case (2D magnetostatic) using PETSc compiled with > both OpenMPI and thread support (both PThreads and OpenMP) on a Ubuntu > 12.04 system. I cannot figure out the results obtained when comparing runs > made using the same number of MPI processes (2) and specifying either no > threads (-threadcomm_type nothread) or 1 OpenMP thread (-threadcomm_type > openmp -threadcomm_nthreads 1). I attached the logs of both runs. It seems > that the communication time has literally exploded. A grep over the logs > gives: > > > > No threading: > > Average time for MPI_Barrier(): 1.38283e-06 > > Average time for zero size MPI_Send(): 7.03335e-06 > > > > 1 OpenMP thread: > > Average time for MPI_Barrier(): 0.00870218 > > Average time for zero size MPI_Send(): 0.00614798 > > > > The same things is occurring when running ksp ex5 (see attached logs). > > > > Any ideas as to what I'm missing? > > > > Many thanks in advance, > > > > Gon?alo > > > <nothread.log><openmp_nthreads_1.log><ex5_nothread.log><ex5_openmp_nthreads_1.log> > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130214/e6152554/attachment.html>
