A few years ago, while I was a graduate student in Greece, I was preparing slides for my talk at the SIAM Parallel Processing 2012 conference. While showing my slides to one of my colleagues, one of his comments was: “All good, but why do you guys doing numerical linear algebra and parallel computing always use the Message Passing Interface to communicate between the processors?”. Having read* the book review of Beresford Parlett in , I did have the wit to imitate Marvin Minsky and reply “Is there any other way?”. Nowadays, this question is even more interesting, and my answer would certainly be longer (perhaps too long!). Execution of programs in distributed computing environments requires communication between the processors. It is then natural to consider by what protocols and guidelines should the processors communicate with each other? This is the question to which the Message Passing Interface (MPI) has been the answer for more than 25 years.