In many cases, configure will find the MPI implementation
automatically.  In some cases, it will need some help.  For example:

For IBM MPI, where the compilation commands are not mpicc and mpif77 etc.:

./configure --with-mpi CC=xlc MPICC=mpcc F77=xlf MPIF77=mpxlf CXX=xlC \
                       MPICXX="mpCC -cpp" F90=xlf90 MPIF90=mpxlf90 \
		       --disable-spawn \
		       --enable-strictmpi

(or the _r versions of the compilers)

You may need to add MPI_SIZEOF_OFFSET=8 .

The option "-cpp" is needed for at least some versions of mpCC to define the
C++ bindings of the MPI routines.

The script that runs the tests assumes that the MPI implementation
supports mpiexec; you should consider this the first test of the implementation.

