[OMPI users] Environment variables [documentation]

[Paul Kapinos]

Dear Open MPI developer,
here:
http://www.open-mpi.org/faq/?category=running#mpi-environmental-variables
are enlisted four envvars Open MPI set for every process. We use they for some
scripting and thank you for providing they.

But simple "mpiexec -np 1 env | grep OMPI" brings lotz more envvars. These are
interesting for us:

1) OMPI_COMM_WORLD_LOCAL_SIZE - seem to contain the number of processes which
are running on the specific node, see also
http://www.open-mpi.org/community/lists/users/2008/07/6054.php

Is this envvar also "stable" as OMPI_COMM_WORLD_LOCAL_RANK is? (This would make
sense as it looks like the OMPI_COMM_WORLD_SIZE, OMPI_COMM_WORLD_RANK pair.)

If yes, maybe it also should be documented in the Wiki page.



2) OMPI_COMM_WORLD_NODE_RANK - is that just a double of
OMPI_COMM_WORLD_LOCAL_RANK ?

Best wishes,
Paul Kapinos

[Ralph Castain]

Post by Paul Kapinos
Dear Open MPI developer,
http://www.open-mpi.org/faq/?category=running#mpi-environmental-variables
are enlisted four envvars Open MPI set for every process. We use they for some scripting and thank you for providing they.
But simple "mpiexec -np 1 env | grep OMPI" brings lotz more enviers.

Yes, we set quite a few more, but those are intended solely for internal use and are not guaranteed. The list on the web site only identifies a set that are guaranteed to be provided.

Post by Paul Kapinos
1) OMPI_COMM_WORLD_LOCAL_SIZE - seem to contain the number of processes which are running on the specific node, see also
http://www.open-mpi.org/community/lists/users/2008/07/6054.php
Is this envvar also "stable" as OMPI_COMM_WORLD_LOCAL_RANK is? (This would make sense as it looks like the OMPI_COMM_WORLD_SIZE, OMPI_COMM_WORLD_RANK pair.)

Yes, and I'll add it to the page

Post by Paul Kapinos
If yes, maybe it also should be documented in the Wiki page.
2) OMPI_COMM_WORLD_NODE_RANK - is that just a double of OMPI_COMM_WORLD_LOCAL_RANK ?

No - the "local rank" is your rank on the node within your own job. The "node rank" is your rank on the node overall. The two differ when you do a comm_spawn. For example, suppose you have two ranks from your initial job on a node, and then comm_spawn three additional ranks. Their values would look like this:

job/rank local_rank node_rank
0/0 0 0
0/1 1 1
1/0 0 2
1/1 1 3
1/2 2 4

Again, I'll add it to the page

Thanks
Ralph

Post by Paul Kapinos
Best wishes,
Paul Kapinos
--
Dipl.-Inform. Paul Kapinos - High Performance Computing,
RWTH Aachen University, Center for Computing and Communication
Seffenter Weg 23, D 52074 Aachen (Germany)
Tel: [phone]
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