MPI4

MPI4 refers to the fourth major revision of the Message Passing Interface (MPI) standard, published by the MPI Forum. It builds on MPI-3 to address contemporary high-performance computing needs, including scalability, heterogeneous architectures, and exascale workloads, by clarifying semantics, expanding capabilities, and offering new mechanisms while maintaining backward compatibility with existing MPI-3 code.

Key additions in MPI-4 include neighborhood collectives, such as neighbor_allgather and neighbor_alltoall families, which enable efficient communication patterns on regular topologies; non-blocking collectives and enhanced persistent communication support to improve overlap and performance; and substantial enhancements to one-sided communications (RMA) with richer synchronization models and atomic operations. MPI-4 also improves shared-memory programming through updated support for shared memory windows and related routines, enabling better exploitation of multi-core nodes. The MPI_T performance tooling interface is extended to facilitate instrumentation, tuning, and portable benchmarking across implementations.

MPI-4 broadens data type and memory model support to aid efficient use on heterogeneous hardware, including accelerators, and emphasizes clearer error handling with more informative diagnostics and predictable failure modes. These changes aim to make MPI more expressive for modern architectures while preserving compatibility with existing MPI-3 applications.

Implementation and adoption vary by vendor, with major MPI libraries such as Open MPI, MPICH, and Intel MPI providing MPI-4 features in current releases. As an evolving standard, MPI-4 encourages developers to leverage new capabilities where beneficial while continuing to maintain portable, scalable MPI code across diverse HPC platforms.