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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130214/9a9b0bb9/attachment-0001.html> -------------- next part -------------- A non-text attachment was scrubbed... Name: nothread.log Type: application/octet-stream Size: 9356 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130214/9a9b0bb9/attachment-0004.obj> -------------- next part -------------- A non-text attachment was scrubbed... Name: openmp_nthreads_1.log Type: application/octet-stream Size: 9375 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130214/9a9b0bb9/attachment-0005.obj> -------------- next part -------------- A non-text attachment was scrubbed... Name: ex5_nothread.log Type: application/octet-stream Size: 13199 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130214/9a9b0bb9/attachment-0006.obj> -------------- next part -------------- A non-text attachment was scrubbed... Name: ex5_openmp_nthreads_1.log Type: application/octet-stream Size: 13244 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130214/9a9b0bb9/attachment-0007.obj>
