Thanks for all your suggestions.
Yes, indeed what I'm trying to do is execute a serial program. All the
documentation you mention was pretty useful.
I have another question, if mpirun launches several copies of the program on
the different hosts, does it mean that I must have a copy of the program on
all the nodes, because I'm using NFS to share the location were my program
is installed and it seems to work fine when I execute mpirun with simple