This document describes the Message-Passing Interface ( MPI) standard, version 2.2. The MPI standard includes point-to-point message-passing, collective communications, group and communicator concepts, process topologies, environmental management, process creation and management, one-sided communications, extended collective operations, external interfaces, I/O, some miscellaneous topics, and a profiling interface. Language bindings for C, C++ and Fortran are defined.

Technically, this version of the standard is based on `` MPI: A Message-Passing Interface Standard, version 2.1, June 23, 2008. The MPI Forum added seven new routines and a number of enhancements and clarifications to the standard.

Historically, the evolution of the standards is from MPI-1.0 (June 1994) to MPI-1.1 (June 12, 1995) to MPI-1.2 (July 18, 1997), with several clarifications and additions and published as part of the MPI-2 document, to MPI-2.0 (July 18, 1997), with new functionality, to MPI-1.3 (May 30, 2008), combining for historical reasons the documents 1.1 and 1.2 and some errata documents to one combined document, and to MPI-2.1 (June 23, 2008), combining the previous documents. This version, MPI-2.2, is based on MPI-2.1 and provides additional clarifications and errata corrections as well as a few enhancements.

(c) 1993, 1994, 1995, 1996, 1997, 2008, 2009 University of Tennessee, Knoxville, Tennessee. Permission to copy without fee all or part of this material is granted, provided the University of Tennessee copyright notice and the title of this document appear, and notice is given that copying is by permission of the University of Tennessee.

Version 2.2: September 4, 2009. This document contains mostly corrections and clarifications to the MPI 2.1 document. A few extensions have been added; however all correct MPI 2.1 programs are correct MPI 2.2 programs. New features were adopted only when there were compelling needs for users, open source implementations, and minor impact on existing MPI implementations.

Version 2.1: June 23, 2008. This document combines the previous documents MPI-1.3 (May 30, 2008) and MPI-2.0 (July 18, 1997). Certain parts of MPI-2.0, such as some sections of Chapter 4, Miscellany, and Chapter 7, Extended Collective Operations have been merged into the Chapters of MPI-1.3. Additional errata and clarifications collected by the MPI Forum are also included in this document.

Version 1.3: May 30, 2008. This document combines the previous documents MPI-1.1 (June 12, 1995) and the MPI-1.2 Chapter in MPI-2 (July 18, 1997). Additional errata collected by the MPI Forum referring to MPI-1.1 and MPI-1.2 are also included in this document.

Version 2.0: July 18, 1997. Beginning after the release of MPI-1.1, the MPI Forum began meeting to consider corrections and extensions. MPI-2 has been focused on process creation and management, one-sided communications, extended collective communications, external interfaces and parallel I/O. A miscellany chapter discusses items that don't fit elsewhere, in particular language interoperability.

Version 1.2: July 18, 1997. The MPI-2 Forum introduced MPI-1.2 as Chapter 3 in the standard " MPI-2: Extensions to the Message-Passing Interface", July 18, 1997. This section contains clarifications and minor corrections to Version 1.1 of the MPI Standard. The only new function in MPI-1.2 is one for identifying to which version of the MPI Standard the implementation conforms. There are small differences between MPI-1 and MPI-1.1. There are very few differences between MPI-1.1 and MPI-1.2, but large differences between MPI-1.2 and MPI-2.

Version 1.1: June, 1995. Beginning in March, 1995, the Message-Passing Interface Forum reconvened to correct errors and make clarifications in the MPI document of May 5, 1994, referred to below as Version 1.0. These discussions resulted in Version 1.1, which is this document. The changes from Version 1.0 are minor. A version of this document with all changes marked is available. This paragraph is an example of a change.

Version 1.0: May, 1994. The Message-Passing Interface Forum (MPIF), with participation from over 40 organizations, has been meeting since January 1993 to discuss and define a set of library interface standards for message passing. MPIF is not sanctioned or supported by any official standards organization.

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

This is the final report, Version 1.0, of the Message-Passing Interface Forum. This document contains all the technical features proposed for the interface. This copy of the draft was processed by LaTeX on May 5, 1994. Please send comments on MPI to mpi-comments@mpi-forum.org. Your comment will be forwarded to MPI Forum committee members who will attempt to respond.

Acknowledgments

This document represents the work of many people who have served on the MPI Forum. The meetings have been attended by dozens of people from many parts of the world. It is the hard and dedicated work of this group that has led to the MPI standard. The technical development was carried out by subgroups, whose work was reviewed by the full committee. During the period of development of the Message-Passing Interface ( MPI), many people helped with this effort. Those who served as primary coordinators in MPI-1.0 and MPI-1.1 are:

• Jack Dongarra, David Walker, Conveners and Meeting Chairs
• Ewing Lusk, Bob Knighten, Minutes
• Marc Snir, William Gropp, Ewing Lusk, Point-to-Point Communication
• Al Geist, Marc Snir, Steve Otto, Collective Communication
• Steve Otto, Editor
• Rolf Hempel, Process Topologies
• Ewing Lusk, Language Binding
• William Gropp, Environmental Management
• James Cownie, Profiling
• Tony Skjellum, Lyndon Clarke, Marc Snir, Richard Littlefield, Mark Sears, Groups, Contexts, and Communicators
• Steven Huss-Lederman, Initial Implementation Subset