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Subject: Re: [OMPI users] Dynamically changing machine file data
From: Christian Bell (christian.bell_at_[hidden])
Date: 2008-02-04 11:42:47

On Fri, 01 Feb 2008, Keith Hellman wrote:

> I'm working on a rather eccentric application of openmpi. Is there
> any way to dynamically change the information obtained from the
> machine or hosts file provided on the command line to mpirun?
> Perhaps something like:
> MPI_Reread_Hosts( const char* hfilepath );

No. Hostfiles and execution environments are the types of
site-specific things that the MPI specification stays away from.

However, you can use MPI_Group_incl on MPI_COMM_WORLD's group and
reorder the ranks to create a new world communicator. This will
allow you to use a new communicator with your reordering but requires
recompilation (and potentially some C macro trickery).

If you can only change the meaning of MPI_COMM_WORLD at runtime, then
it's significantly more complicated but is feasible using the MPI
profiling interface. Follow-up with more specific information if
this is the type of thing you want to do.

    . . christian

(QLogic Host Solutions Group, formerly Pathscale)