MPI: Difference between revisions

The Message Passing Interface (MPI) is, strictly speaking, a ''standard'' describing a set of subroutines, functions, objects, ''etc.'', with which one can write parallel programs. Many different ''implementations'' of the standard have been produced, such as Open MPI, MPICH, and MVAPICH. The standard describes how MPI should be called from Fortran, C, and C++ languages, but unofficial "bindings" can be found for several other languages.

MPI is an open, non-proprietary standard so an MPI program can easily be ported to many different computers. Applications that use it can be run on a large number of processors at once, often with good efficiency (called "scalability"). And because memory is local to each process some aspects of debugging are simplified --- it isn't possible for one process to interfere with the memory of another, and if a program generates a segmentation fault the resulting core file can be processed by standard serial debugging tools. However, due to the need to manage communication and synchronization explicitly, MPI programs may appear more complex than programs written with tools that support implicit communication. Furthermore, in designing an MPI program one should take care to minimize communication overhead in order that it not overwhelm the speed-up gained from parallel computation.

As we turn now to consider the basics of programming with MPI, we will attempt to highlight a few of the issues that arise and discuss strategies to avoid them. Suggested references are presented at the end of this tutorial and the reader is encouraged to consult them for additional information.