SIDEBAR ON Message Passing Interface Forum

During the past year there has been quite a bit of activity in the community to develop a standard interface for message passing [1]. The main advantages of establishing a message passing standard are portability and ease-of-use. In a distributed memory communication environment in which the higher level routines and/or abstractions are built upon lower level message passing routines the benefits of standardization are particularly apparent. Furthermore, the definition of a message passing standard provides vendors with a clearly defined base set of routines that they can implement efficiently, or in some cases provide hardware support for, thereby enhancing scalability. The standards activity goes by the name Message Passing Interface Forum (MPI Forum) and is composed of the major hardware and software vendors, as well as researchers from universities and laboratories around the world.

The goal of the Message Passing Interface simply stated is to develop a standard for writing message-passing programs. As such the interface should establishing a practical, portable, efficient, and flexible standard for message passing.

A complete list of goals follow.

• Design an application programming interface (not necessarily for compilers or a system implementation library).
• Allow efficient communication: Avoid memory to memory copying and allow overlap of computation and communication and offload to communication coprocessor, where available.
• Allow (but no mandate) extensions for use in heterogeneous environment.
• Allow convenient C, Fortran 77, Fortran 90, and C++ bindings for interface.
• Provide a reliable communication interface: User need not cope with communication failures. Such failures are dealt by the underlying communication subsystem.
• Focus on a proposal that can be agreed upon in 6 months.
• Define an interface that is not too different from current practice, such as PVM, Express, Parmacs, etc.
• Define an interface that can be quickly implemented on many vendor's platforms, with no significant changes in the underlying communication and system software.
• The interface should not contain more functions than are really necessary.

This standard is intended for use by all those who want to write portable message-passing programs in Fortran 77 and/or C. This includes individual application programmers, developers of software designed to run on parallel machines, and creators of higher-level programming languages, environments, and tools. In order to be attractive to this wide audience, the standard must provide a simple, easy-to-use interface for the basic user while not semantically precluding the high-performance message-passing operations available on advanced machines.

The standard includes (this is temporarily as inclusive as possible):

• Point-to-point communication in a variety of modes, including modes that allow fast communication and heterogeneous communication
• Collective operations
• Process groups
• Communication contexts
• A simple way to create processes for the SPMD model
• Bindings for both Fortran and C
• A model implementation
• A formal specification.

One of the objectives of the activity is to have a definition completed by the Summer 1993. If you are interested in finding out more about the MPI effort contact David Walker (walker@msr.epm.ornl.gov) at Oak Ridge National Laboratory.