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Subject: Re: [OMPI users] Outputting rank and size for all outputs.
From: Ashley Pittman (apittman_at_[hidden])
Date: 2008-06-24 11:36:22

If you are using the openmpi mpirun then you can put the following in a
wrapper script which will prefix stdout in a manner similar to what you
appear to want. Simply add the wrapper script before the name of your

Is this the kind of thing you were aiming for? I'm quite surprised
mpirun doesn't have an option for this actually, it's a fairly common
thing to want.

Ashley Pittman.


$@ | sed "s/^/\[rk:$OMPI_MCA_ns_nds_vpid,sz:$OMPI_MCA_ns_nds_num_procs

On Tue, 2008-06-24 at 11:06 -0400, Mark Dobossy wrote:
> Lately I have been doing a great deal of MPI debugging. I have, on an
> occasion or two, fallen into the trap of "Well, that error MUST be
> coming from rank X. There is no way it could be coming from any other
> rank..." Then proceeding to debug what's happening at rank X, only to
> find out a few frustrating hours later that rank Y is throwing the
> output (I'm sure no one else out there has fallen into this trap). It
> was at that point, I decided to write up some code to automatically
> (sort of) output the rank and size of my domain with every output. I
> write mostly in C++, and this is what I came up with:
> #include <iostream>
> #include <mpi.h>
> std::ostream &mpi_info(std::ostream &s) {
> int rank, size;
> rank = MPI::COMM_WORLD.Get_rank();
> size = MPI::COMM_WORLD.Get_size();
> s << "[rk:" << rank << ",sz:" << size << "]: ";
> return s;
> }
> Then in my code, I have changed:
> std::cerr << "blah" << std::endl;
> to:
> std::cerr << mpi_info << "blah" << std::endl;
> (or cout, or file stream, etc...)
> where "blah" is some amazingly informative error message.
> Are there other ways people do this? Simpler ways perhaps?
> -Mark
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