The MPI/SX Implementation of MPI for NEC's SX-6 and other NEC Platforms

MPI is the standard communication interface for programming parallel applications in the message passing paradigm. MPI/SX is a dedicated, efficient and highly optimized implementation of the full MPI-2 standard for the NEC SX-series of parallel vector supercomputers. MPI/SX is also the basis for implementations of MPI for other NEC parallel platforms, for instance MPI/EX for AzusA and AsAmA, and for the Earth Simulator. This paper gives an overview of the key features and recent developments of MPI/SX. Among these are: highly optimized point-to-point and one-sided communications both within a single, shared-memory node and across nodes; optimized collective operations; efficient, vectorized handling of non-contiguous user data; and a non-trivial implementation of the MPI topology functionality. Although particular attention has been paid to efficient utilization of the vector-capabilities of the SX-machines, the architecture and optimizations of MPI/SX are immediately applicable to other NEC architectures.