On Wed, Jul 23, 2014 at 12:32 AM, Sikandar Mashayak <symasha...@gmail.com> wrote: > Hi, > > I am checking out GPU performance of Gromacs5.0 on a single node of a > cluster. > The node has two 8-core Sandy Bridge Xeon E5-2670 and two NVIDIA K20x GPUs. > > My question - is there a restriction on how many number of MPI tasks can be > used per GPU task?
No, there is none. In fact, it is rarely optimal to run only one PP rank per GPU, that is two (PP) ranks in a dual socket/GPU node. However, using two ranks per physical core, that is 32 per node if you have HT enabled is not advantageous. > I observe that I could only perform mdrun with same number of MPI tasks as > GPU tasks. I use one OpenMP thread per MPI task. If I use more MPI tasks > than no. of GPUs, I get an error: > > > Fatal error: > Incorrect launch configuration: mismatching number of PP MPI processes and > GPUs per node. > mdrun_mpi was started with 4 PP MPI processes per node, but you provided 2 > GPUs. You are not providing the correct PP rank to GPU mapping; please consult the docs: http://www.gromacs.org/Documentation/Acceleration_and_parallelization#Heterogenous_parallelization.3a_using_GPUs Cheers, -- Szilárd > Thanks, > Sikandar > -- > Gromacs Users mailing list > > * Please search the archive at > http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! > > * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists > > * For (un)subscribe requests visit > https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a > mail to gmx-users-requ...@gromacs.org. -- Gromacs Users mailing list * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists * For (un)subscribe requests visit https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a mail to gmx-users-requ...@gromacs.org.