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What is MPI?

An Interface Specification

M P I = Message Passing Interface

MPI is a specification for the developers and users of message passing libraries. By itself, it is NOT a library - but rather the specification of what such a library should be.

MPI primarily addresses the message-passing parallel programming model: data is moved from the address space of one process to that of another process through cooperative operations on each process.

Simply stated, the goal of the Message Passing Interface is to provide a widely used standard for writing message passing programs. The interface attempts to be:

The MPI standard has gone through a number of revisions, with the most recent version being MPI-3.x

Interface specifications have been defined for C and Fortran90 language bindings:

Actual MPI library implementations differ in which version and features of the MPI standard they support. Developers/users will need to be aware of this.

Programming Model

Originally, MPI was designed for distributed memory architectures, which were becoming increasingly popular at that time (1980s - early 1990s).

Distributed Memory

As architecture trends changed, shared memory SMPs were combined over networks creating hybrid distributed memory / shared memory systems.

MPI implementors adapted their libraries to handle both types of underlying memory architectures seamlessly. They also adapted/developed ways of handling different interconnects and protocols.

Hybrid Memory

Today, MPI runs on virtually any hardware platform:

The programming model clearly remains a distributed memory model however, regardless of the underlying physical architecture of the machine.

All parallelism is explicit: the programmer is responsible for correctly identifying parallelism and implementing parallel algorithms using MPI constructs.

Reasons for Using MPI

History and Evolution: (for those interested)

MPI has resulted from the efforts of numerous individuals and groups that began in 1992. Some history:

MPI Evolution


Documentation for all versions of the MPI standard is available at: