What MPI Does and Does Not Specify

The standard specifies the form of the following.

• Point to point communications, that is, messages between pairs of processes.
• Collective communications: communication or synchronization operations that involve entire groups of processes.
• Process groups: how they are used and manipulated.
• Communicators: a mechanism for providing separate communication scopes for modules or libraries. Each communicator specifies a distinct name space for processes, a distinct communication context for messages and may carry additional, scope-specific information.
• Process topologies: functions that allow the convenient manipulation of process labels, when the processes are regarded as forming a particular topology, such as a Cartesian grid.
• Bindings for Fortran 77 and ANSI C: MPI was designed so that versions of it in both C and Fortran had straightforward syntax. In fact, the detailed form of the interface in these two languages is specified and is part of the standard.
• Profiling interface: the interface is designed so that runtime profiling or performance-monitoring tools can be joined to the message-passing system. It is not necessary to have access to the MPI source to do this and hence, portable profiling systems can be easily constructed.
• Environmental management and inquiry functions: these functions give a portable timer, some system-querying capabilities, and the ability to influence error behavior and error-handling functions.

• shared-memory operations
• interrupt-driven messages, remote execution, and active messages
• program construction tools
• debugging support
• thread support
• process or task management
• input and output functions

The remainder of this article discusses some of the more interesting features of MPI.