Modern networked computing environments and applications often require---or can benefit from---the use of multiple communication substrates, transport mechanisms, and protocols, chosen according to where communication is directed, what is communicated, or when communication is performed. We propose techniques that allow multiple communication methods to be supported transparently in a single application, with either automatic or user-specified selection criteria guiding the methods used for each communication. We explain how communication link and remote service request mechanisms facilitate the specification and implementation of multimethod communication. These mechanisms have been implemented in the Nexus multithreaded runtime system, and we use this system to illustrate solutions to various problems that arise when implementing multimethod communication. We also illustrate the application of our techniques by describing a multimethod, multithreaded implementation of the Message Pas...

High-speed wide-area networks enable innovative ap-plications that integrate geographically distributed com-puting, database, graphics, and networking resources. The Message Passing Interface (MPI) can be used as a portable, high-performance programming model for such systems. However, the wide-area environment in-troduces challenging problems for the MPI implementor, because of the heterogeneity of both the underlying physical infrastructure and the authentication and software environment at different sites. In this article, we describe an MPI implementation that incorporates so-lutions to these problems. This implementation, which was developed for the I-WAY distributed-computing ex-periment, was constructed by layering MPICH on the Nexus multithreaded runtime system. Nexus provides automatic configuration mechanisms that can be used to select and configure authentication, process creation, and communication mechanisms in heterogeneous systems.

We propose extensions to the Message Passing Interface (MPI) that generalize the MPI communicator concept to allow multiple communication endpoints per process, dynamic creation of endpoints, and the transfer of endpoints between processes. The generalized communicator construct can be used to express a wide range of interesting communication structures, including collective communication operations involving multiple threads per process, communications between dynamically created threads, and object-oriented applications in which communications are directed to specific objects. Furthermore, this enriched functionality can be provided in a manner that preserves backward compatibility with MPI. We describe the proposed extensions, illustrate their use with examples, and discuss implementation issues. 1. Introduction One of the most important features of the Message Passing Interface (MPI) [4, 7] is the communicator, which allows the programmer to define unique communication spaces with...

Abstract We propose extensions to the Message Passing Interface (MPI) that generalize the MPI communicator concept to allow multiple communication endpoints per process, dynamic creation of endpoints, and the transfer of endpoints between processes. The generalized communicator construct can be used to express a wide range of interesting communication structures, including collective communication operations involving multiple threads per process, communications between dynamically created threads or processes, and object-oriented applications in which communications are directed to specific objects. Furthermore, this enriched functionality can be provided in a manner that preserves backward compatibility with MPI. We describe the proposed extensions, illustrate their use with examples, and describe a prototype implementation in the popular MPI implementation MPICH.