Abstract. To better manage the ever increasing complexity of LAM/MPI, we have created a lightweight component architecture for it that is specifically designed for high-performance message passing. This paper describes the basic design of the component architecture, as well as some of the particular component instances that constitute the latest release of LAM/MPI. Performance comparisons against the previous, monolithic, version of LAM/MPI show no performance impact due to the new architecture—in fact, the newest version is slightly faster. The modular and extensible nature of this implementation is intended to make it significantly easier to add new functionality and to conduct new research using LAM/MPI as a development platform. 1

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