OpenSHMEM: Towards a Unified RMA Model

Abstract

For many problem domains, one-sided communication paradigms, such as RMA (remote memory access), dominate the solution space on massively parallel systems through their ability to preserve problem tractability, high scalability, and overall performance. How- ever, unlike the MPI standard for two-sided communication, there is no single, successful standard RMA model or interface for one-sided communication, though the SHMEM family of APIs have a long history of success spanning many years and multiple platforms. While the various SHMEM implementations have remained similar across numerous implementations, the subtle differences have hindered acceptance, portability, and in some cases, program cor- rectness. In this paper, we will discuss the differences between SHMEM implementations and contrast SHMEM with other extant libraries supporting RMA semantics to provide motivation for a standards-based OpenSHMEM with the requisite breadth of functionality.