Running code in parallel

We have now successfully completed the prerequisites for the running of code on multiple machines. We will now learn how to run our code on the Raspberry Pi cluster using the MPICH library. We will first run a demo included with the mpi4py module, and then we will run an N-Body simulation on our cluster. Sounds fun? Let's get into it.

First, we need to tell the MPICH library the IP address of each of the Pis in our network. This is done by simply creating a new file called machinefile in the home folder, which contains a list of the IP addresses of all the Raspberry Pis connected to our network. Execute the following command to create the file:

nano machinefile

Then, add the IP address of each Raspberry Pi in a new line so that the final result looks like this:

Note that we have added three IP addresses because two Raspberry Pis are slaves and one is a master. So, the MPICH library knows that it needs to run the code on these three devices. Also, note that MPICH does...