Evaluating Contexts in OpenSHMEM-X Reference Implementation

Many-core processors are now ubiquitous in supercomputing. This evolution pushes toward the adoption of mixed models in which cores are exploited with threading models (and related programming abstractions, such as OpenMP), while communication between distributed memory domains employ a communication Application Programming Interface (API). OpenSHMEM is a partitioned global address space communication specification that exposes one-sided and synchronization operations. As the threaded semantics of OpenSHMEM are being fleshed out by its standardization committee, it is important to assess the soundness of the proposed concepts. This paper implements and evaluate the ``context'' extension in relation to threaded operations. We discuss the implementation challenges of the context and the associated API in OpenSHMEM-X. We then evaluate its performance in threaded situations on the Infiniband network using micro-benchmarks and the Random Access benchmark and see that adding communication contexts significantly improves message rate achievable by the executing multi-threaded PEs.