Hello,
Two questions from an old MPI user who's still learning.
Let's assume mpirun's spawned N copies of program A and M (/=N) copies of
program B. This execution option leads A and B processes to belong to the
same MPI_COMM_WORLD and ranks are ordered consequently from 0 to N-1 for A
and from N to (N+M)-1 for B.
Now, since A and B are two independent programs, let's consider that
MPI_COMM_WORLD has to be splitted into two communicator groups using
MPI_Comm_split. Then, as we know, the color argument must be set so that
its value is different for A and B.
Q1: A part from setting it as a constant in A and B or reading it from a
file, is there a more elegant way to set it automatically so that
color(A) is always different from color(B)?
Furthermore, let's consider that MPI_COMM_WORLD has been splitted into A
and B groups anyway. We want to create an inter-communicator between them
using MPI_Intercomm_create. Group B can always set the peer_leader rank
process of A as 0.
Q2: Is there a MPI-1 solution that can return to A any peer_leader (or first)
rank of the remote group B?
Both questions Q1 and Q2 can be bypassed using MPI_Comm_spawn or
server/client base processing or a combination of both. But this is not my
aim since the constraint is to stick to a MPI-1 implementation to execute
such MPMD applications on some special architecture like BlueGene machine.
Thanks a lot for your help.
Regards,
Jalel
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