If you get 
<PRE>
<CODE>
mpicc: Command not found.
</CODE>
</PRE>
or something similar, your <CODE>PATH</CODE> doesn't contain the location of
the MPI commands.  You may need something like (for the MPICH implementation)
<PRE>
<CODE>
setenv PATH /usr/local/mpi/lib/sun4/ch_p4:/usr/local/mpi/bin:$PATH
rehash
</CODE>
</PRE>
or something similar.  The exact path will depend on your MPI installation and
the devices that you are using.
<P>
The MPI standard does not specify how MPI programs are compiled or run; this
is up to the implementation.  The examples here are for the MPICH
implementation. 
<P>
If your program runs, but runs with only one processor, you have be accessing
an <CODE>mpirun</CODE> for a different version of MPI.  Give the command
<PRE>
<CODE>
which mpirun
</CODE>
</PRE>
and make sure that the PATH given matches the one that cooresponds to the MPI
implementation that you are using.
