Message Passing Interface (MPI) is a specification for software developers used to make use of a cluster of computers. A set of libraries exist for using this standard on modern day (High Performance Computing) HPC Clusters. The problem with a computing cluster is that while some of the CPUs share memory (Shared Memory), others have a distributed memory architecture which is only connected by network. Today’s developers are able to make use of these distributed memory, shared memory and a hybrid system of both; all with the power of MPI. Over the years, there have been quite a few MPI libraries available, and today, some of the more common libraries include MPICH, MVAPICH, Open MPI and Intel MPI. We also have quite a few applications that have already been ported to run by using MPI.