OpenSHMEM Reference Implementation using UCCS-uGNI Transport Layer

OpenSHMEM is a library interface implementation and specification that enables the implementation of the Partitioned Global Address Space (PGAS) model. It exports modern RDMA network functionality and communication semantics to applications very efficiently. There are many closed source implementations of OpenSHMEM for modern RDMA interconnects such as InfiniBand and Cray's Gemini and Aries. Given the important role that Cray systems play in HPC, in this paper, we present an open source implementation of OpenSHMEM for Cray XE/XK/XC systems. To implement OpenSHMEM, we use the uGNI interface. uGNI is a generic interface that is designed for multiple programming models. The interface fits well the goal of UCCS. Having OpenSHMEM with UCCS-uGNI allows usage of the same implementation over multiple interconnects. This also translates into many advantages that come with common code such as resource sharing, increasing productivity because of less code maintenance, etc. Preliminary results show that OpenSHMEM-UCCS performs comparable to state-of-the-art Cray SHMEM for Put, Get, and AMO operations.