I'm getting a very suprising result with the attached application and configfile. As you can see, I'm asking MPI to run 2 processes on Shakespeare, and 2 on Burns. But when I ran the program using mpiexec -configfile ./MPI_config.txt what I actually get is the output shown in MPI_IO_Test.txt. Furthermore I can confirm that this is genuine: I shut down Burns altogether and the same result ensues. It's as if mpiexec is taking the -host field as advisory but not required, that is, it might execute on the host asked for, but then again if it decides not to, it doesn't interpret the -host field as a requirement. I get the distinct impression, indeed, that instead of interpreting the host as a requirement, it uses a greedy process allocation: if it can spawn all of the processes on the invoking host (the one that ran mpiexec) it does so, and only once the resources there are exhausted does it look at other possible hosts. Clearly if you specify a -host the intention is that the process should be placed there. This looks like a bug in mpiexec. _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss