[Beowulf] Simple MPI programs hang

[Bill Rankin]

On Mar 19, 2008, at 7:31 PM, Gregg Germain wrote:

> Hi everyone,
>
> I've created a 2 node cluster running FC8.  I've installed MPICH2  
> 1.0.6pl on both (not NFS'd).
>
> The Master, Ragnar, is a 64 bit; olaf is a 32 bit.
>
> I set up the ring, and mpdtrace shows:
>
> $ mpdtrace -l
> Ragnar_37601 (192.168.0.2)
> olaf_45530 (192.168.0.5)
> $
>
> I run a VERY simple MPI program and it hangs:
> #include "mpi.h"
> #include <stdio.h>
> #include <math.h>
> #include <string.h>
>
> int main( int argc, char *argv[] )
> {
>   MPI_Init(&argc,&argv);
>   printf("Hello!\n");
>   MPI_Finalize();
>   return 0;
> }
>

If it's not a 32/64 bit issue (as the other poster mentioned) you  
should try putting an MPI_Barrier() call immediately before the  
MPI_Finalize().  This will at least make sure that both instances  
have made it complete through MPI_Init() before the one or the other  
one exits.

-bill