[Beowulf] compilers vs mpi?

[Mark Hahn]

Hi all,
I'm interested in hearing about experiences with mixing compilers
between the application and MPI.  that is, I would like to be able
to compile MPI (say, OpenMPI) with gcc, and expect it to work correctly 
with apps compiled with other compilers.  I guess I'm reasoning by analogy 
to normal distro libs.

the OpenMPI FAQ has this comment:

NOTE: The Open MPI team recommends using a single compiler suite whenever
possible. Unexpeced or undefined behavior can occur when you mix compiler
suites in unsupported ways (e.g., mixing Fortran 77 and Fortran 90 compilers
between different compiler suites is almost guaranteed not to work).

and there are complaints elsewhere in the FAQ about f90 bindings.  I'd 
appreciate it if someone could help a humble C/C++/perl hacker understand 
the issues here...

thanks, mark hahn.
PS: we have a large and diverse user base, so tend to have to support 
gcc, intel, pathscale and pgi.  we even have people who want to use 
intel's damned synthetic 128b FP over MPI :(