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.

  MPI 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.

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

• Practical
• Portable
• Efficient
• Flexible

The MPI standard has gone through a number of revisions, with the most recent version being MPI-5.0 .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.

Parallel Computer Memory Architectures

Shared Memory

General Characteristics

• Shared memory parallel computers vary widely, but generally have in common the ability for all processors to access all memory as global address space.
• Multiple processors can operate independently but share the same memory resources.
• Changes in a memory location effected by one processor are visible to all other processors.
• Historically, shared memory machines have been classified as UMA and NUMA, based upon memory access times.

Uniform Memory Access (UMA)