Message Passing Interface

Message Passing Interface (MPI) is a standardized and portable message-passing standard designed by a group of researchers from academia and industry to function on a wide variety of parallel computing architectures. The standard defines the syntax and semantics of a core of library routines useful to a wide range of users writing portable message-passing programs in C, C++, and Fortran. There are several well-tested and efficient implementations of MPI, many of which are open-source or in the public domain. These fostered the development of a parallel software industry, and encouraged development of portable and scalable large-scale parallel applications. Message Passing Interface (MPI) is a standardized and portable message-passing standard designed by a group of researchers from academia and industry to function on a wide variety of parallel computing architectures. The standard defines the syntax and semantics of a core of library routines useful to a wide range of users writing portable message-passing programs in C, C++, and Fortran. There are several well-tested and efficient implementations of MPI, many of which are open-source or in the public domain. These fostered the development of a parallel software industry, and encouraged development of portable and scalable large-scale parallel applications. The message passing interface effort began in the summer of 1991 when a small group of researchers started discussions at a mountain retreat in Austria. Out of that discussion came a Workshop on Standards for Message Passing in a Distributed Memory Environment held on April 29–30, 1992 in Williamsburg, Virginia. Attendees at Williamsburg discussed the basic features essential to a standard message-passing interface and established a working group to continue the standardization process. Jack Dongarra, Tony Hey, and David W. Walker put forward a preliminary draft proposal, 'MPI1', in November 1992. In November 1992 a meeting of the MPI working group took place in Minneapolis and decided to place the standardization process on a more formal footing. The MPI working group met every 6 weeks throughout the first 9 months of 1993. The draft MPI standard was presented at the Supercomputing '93 conference in November 1993. After a period of public comments, which resulted in some changes in MPI, version 1.0 of MPI was released in June 1994. These meetings and the email discussion together constituted the MPI Forum, membership of which has been open to all members of the high-performance-computing community. The MPI effort involved about 80 people from 40 organizations, mainly in the United States and Europe. Most of the major vendors of concurrent computers were involved in MPI - along with researchers from universities, government laboratories, and industry. MPI provides parallel hardware vendors with a clearly defined base set of routines that can be efficiently implemented. As a result, hardware vendors can build upon this collection of standard low-level routines to create higher-level routines for the distributed-memory communication environment supplied with their parallel machines. MPI provides a simple-to-use portable interface for the basic user, yet one powerful enough to allow programmers to use the high-performance message passing operations available on advanced machines. In an effort to create a universal standard for message passing, researchers incorporated the most useful features of several systems into MPI, rather than choosing one system to adopt as a standard. They adopted features from systems by IBM, Intel, nCUBE, PVM, Express, P4 and PARMACS. The message-passing paradigm is attractive because of wide portability and can be used in communication for distributed-memory and shared-memory multiprocessors, networks of workstations, and a combination of these elements. The paradigm can apply in multiple settings, independent of network speed or of memory architecture. Support for MPI meetings came in part from DARPA and from the US National Science Foundation under grant ASC-9310330, NSF Science and Technology Center Cooperative agreement number CCR-8809615, and from the Commission of the European Community through Esprit Project P6643. The University of Tennessee also made financial contributions to the MPI Forum. MPI is a communication protocol for programming parallel computers. Both point-to-point and collective communication are supported. MPI 'is a message-passing application programmer interface, together with protocol and semantic specifications for how its features must behave in any implementation.' MPI's goals are high performance, scalability, and portability. MPI remains the dominant model used in high-performance computing today. MPI is not sanctioned by any major standards body; nevertheless, it has become a de facto standard for communication among processes that model a parallel program running on a distributed memory system. Actual distributed memory supercomputers such as computer clusters often run such programs. The principal MPI-1 model has no shared memory concept, and MPI-2 has only a limited distributed shared memory concept. Nonetheless, MPI programs are regularly run on shared memory computers, and both MPICH and Open MPI can use shared memory for message transfer if it is available. Designing programs around the MPI model (contrary to explicit shared memory models) has advantages over NUMA architectures since MPI encourages memory locality. Explicit shared memory programming was introduced in MPI-3.