SCI networking for shared-memory computing in UPC: blueprints of the GASNet SCI conduit

Abstract

Unified Parallel C (UPC) is a programming model for shared-memory parallel computing on shared- and distributed-memory systems. The Berkeley UPC software, which operates on top of their Global Addressing Space Networking (GASNet) communication system, is a portable, high-performance implementation of UPC for large-scale clusters. The Scalable Coherent Interface (SCI), a torus-based system-area network (SAN), is known for its ability to provide very low latency transfers as well as its direct support for both shared-memory and message-passing communications. High-speed clusters constructed around SCI promise to he a potent platform for large-scale UPC applications. This work introduces the design of the core API for the new SCI conduit for GASNet and UPC, which is based on active messages (AM). Latency and bandwidth data were collected and are compared with raw SCI results and with other existing GASNet conduits. The outcome shows that the new GASNet SCI conduit is able to provide promising performance in support of UPC applications.