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Subject: [OMPI devel] how should processes be mapped to nodes?
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2009-10-08 10:33:03


If I specify two hosts and no "slots" information, processes should be
started in equal numbers on the two hosts. But, how should they be
ranked? "Block" or "cyclic" (round robin)? Did we change this behavior
recently?

% ompi_info | grep "Open MPI:"
                Open MPI: 1.3.4a1r22009
% mpirun -H saem9,saem10 -np 8 -tag-output hostname
[1,0]<stdout>:saem9
[1,1]<stdout>:saem9
[1,2]<stdout>:saem9
[1,3]<stdout>:saem9
[1,4]<stdout>:saem10
[1,5]<stdout>:saem10
[1,6]<stdout>:saem10
[1,7]<stdout>:saem10

% ompi_info | grep "Open MPI:"
                Open MPI: 1.3.4a1r22051
% mpirun -H saem9,saem10 -np 8 -tag-output hostname
[1,0]<stdout>:saem9
[1,1]<stdout>:saem10
[1,2]<stdout>:saem9
[1,3]<stdout>:saem10
[1,4]<stdout>:saem9
[1,5]<stdout>:saem10
[1,6]<stdout>:saem9
[1,7]<stdout>:saem10