Hi I was about tell that i have written an MPI code in which i have specified only for the communication between nodes and i dont whether can i run program as per my requirement i.e to use the cores present in my node (all 4 cores). So my doubt is should i need to include pthreads or the program which i have written is sufficient.
My program gives the output has MPI-size=4 time at node1: time at node 2: time at node3: time at node 4: This is what i was explaining. On Tue, Aug 14, 2012 at 2:17 PM, Jeff Squyres <jsquy...@cisco.com> wrote: > On Aug 14, 2012, at 7:55 AM, seshendra seshu wrote: > > > I haven't still changed my code to run when threading is needed > (presently working). > > I'm afraid I can't parse that sentence; I don't know what you mean. > > > I have doubt that when i calculate the MPI ranks using the MPI command > it gives only the nodes which have given in a host file. > > I'm not sure what this is saying, either. Sorry! :-( > > If you are running in a scheduled environment (e.g., under the SLURM or > Torque/PBS schedulers), then Open MPI will find out from the schedule how > many processors are on that machine and react accordingly. > > Otherwise, if you are running in an unscheduled environment (e.g., if you > just specify a hostfile to tell Open MPI where to run), then you need to > tell Open MPI how many processes you want it to launch on each node. Per > Tom's advice, we usually recommend running -- at most -- one MPI process > per core. > > > But how can i calculate the MPI ranks as you have told i.e N=H( > number of CPUs showing on a node ) x M ( number of nodes in a cluster). > > Use the Hwloc utility "lstopo" to give you a graphical depiction of the > internal topology of your machine(s). > http://www.open-mpi.org/projects/hwloc/ > > Then you can count how many cores are on your machine and set your > hostfile accordingly. > > > And I would like test like this if have 2 nodes and where I can use up > to 50 cores. I would like to scale like 2,4,8,16,32,45 cores and at the > same time if use 8 cores then I would like to take the readings as node1- > 3cores and node2-5 cores. So in order to do that should I need mention > anything in the host file as I have mentioned the No.of nodes. > > In general, just list how many slots you have on each machine in the > hostfile and then use mpirun's -np and -npernode options to specify how > many total processes to run and how many to run per machine. For example: > > ----- > shell$ cat hostfile > # This hostfile represents 2 Intel Romley-based servers; 16 cores each > server1 slots=16 > server2 slots=16 > shell$ mpirun --hostfile hostfile -np 4 --npernode 2 my_mpi_executable > # ^^ this runs a total of 4 MPI processes, 2 on each node > shell$ mpirun --hostfile hostfile -np 16 --npernode 8 my_mpi_executable > # ^^ this runs a total of 16 MPI processes, 8 on each node > ----- > > ...and so on. > > -- > Jeff Squyres > jsquy...@cisco.com > For corporate legal information go to: > http://www.cisco.com/web/about/doing_business/legal/cri/ > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > -- WITH REGARDS M.L.N.Seshendra
