Ah, yes - so here is what is happening. When no slot info is provided, we use the number of detected cores on each node as the #slots. So if you want to loadbalance across the nodes, you need to set —map-by node
Or add slots=1 to each line of your host file to override the default behavior > On Nov 7, 2014, at 8:52 AM, Blosch, Edwin L <edwin.l.blo...@lmco.com> wrote: > > Here’s my command: > > <path_to_OpenMPI_1.8.3>/bin/mpirun <unrelated MCA options> --machinefile > hosts.dat -np 4 <executable> > > Here’s my hosts.dat file: > > % cat hosts.dat > node01 > node02 > node03 > node04 > > All 4 ranks are launched on node01. I don’t believe I’ve ever seen this > before. I had to do a sanity check, so I tried MVAPICH2-2.1a and got what I > expected: 1 process runs on each of the 4 nodes. The mpirun man page says > ‘round-robin’, which I take to mean that one process would be launched per > line in the hosts file, so this really seems like incorrect behavior. > > What could be the possibilities here? > > Thanks for the help! > > > > _______________________________________________ > users mailing list > us...@open-mpi.org <mailto:us...@open-mpi.org> > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > <http://www.open-mpi.org/mailman/listinfo.cgi/users> > Link to this post: > http://www.open-mpi.org/community/lists/users/2014/11/25707.php > <http://www.open-mpi.org/community/lists/users/2014/11/25707.php>
