Now that we have MPI installed and working we can start using it with real programming languages, and first language of choice for the Pi is ofcourse Python.
Following on with the instructions from Southampton Uni there is some information at the bottom about the use of mpi4py one of a number of Python libraries for MPI.
MPI4PY can be installed through apt-get
sudo apt-get install python-mpi4py
Once installed we can pull down some demo code
mkdir mpi4py cd mpi4py wget http://mpi4py.googlecode.com/files/mpi4py-1.3.tar.gz tar xfz mpi4py-1.3.tar.gz cd mpi4py-1.3/demo
And once its installed we can check it works by running one of the basic examples
mpirun.openmpi -np 2 -machinefile /home/pi/mpi_testing/machinefile python helloworld.py
This produces the following output if running on one node, in this instance pislave1
Hello, World! I am process 0 of 2 on pislave1. Hello, World! I am process 1 of 2 on pislave2.
The above instructions can now be repeated on pimaster, and pislaves2, 3 and 4