[MPICH] Problem with MPICH2 mpiexec with different executables

[Matthew Siegel]

Hi all,

Thanks for the help in advance.  Here's a detailed explanantion of the
problem I'm running in to.

A little background . . . I am running the latest MPICH2.  I am using Rocks,
running on Xeon EM64T processors with Gig-E IP between the compute nodes.
Not completely relevant, but want to be complete.

I have written an app that has the following source code.  It is a very very
simple because my real program which is quite complicated was not working,
and I figured that this app would work just fine.

#include <mpi.h>
#include <stdio.h>

int main(int argc, char** argv) {
    MPI::Init(argc, argv);
    printf("My app is running!!!!\n");
    MPI::Finalize();
    return 0;
}

I compiled it like this:
    mpicxx -o my_app my_app.cpp

I start an mpd daemon on the the head node 'mpd &', and verify with
mpdtrace.  So far so good.

I then execute the following:
    mpiexec -l -n 1 ./myapp

and I get:
    0: My app is running!!!!

and it quits.  I then run:
    mpiexec -l -n 4 ./myapp

and I get (as expected):
    0: My app is running!!!!
    1: My app is running!!!!
    3: My app is running!!!!
    2: My app is running!!!!

OK, so this is good so far.   Here's where things go awry...

I then run:
    mpiexec -l -n 1 hostname : -n 1 date

and I get (again as expected):
    0: <hostname>
    1: <date>

Then I run (and here's where the problem is):
    mpiexec -l -n 1 ./myapp : -n 1 hostname

and I get:
    1: <hostname>

And NOTHING else!  Just hangs FOREVER . . . have to hit CTRL-C to quit.

This continues regardless of the order that I run my app in, whether it's
the first or second on the line, it does not matter.  Also, this is true
regardless of the "other" app that I am running, not necessarilly just
'hostname' or 'date', and does not matter how many nodes that I am using.
The real apps that I am trying to run both are using MPI and am trying to
pass data between the two processes.  I have rebuilt MPICH2 multiple times,
and tried various configure options with zero luck.

Please help, this has become a showstopper for me.

Thanks!

Matt
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