This report introduces the Scatter-Gather parallel-programming and parallel execution model in the form of a simple imperative language named SGL. Its design is based on past experience with Bulk-synchronous parallel (BSP) programming and BSP language design. SGL's novel features are motivated by the last decade's move towards multi-level and heterogeneous parallel architectures involving multi-core processors, graphics accelerators and hierarchical routing networks in the largest multiprocessing systems. The design of SGL is coherent with Valiant's Multi-BSP while off ering a programming interface that is even simpler than the primitives of Bulk-Synchronous parallel ML (BSML). SGL appears to cover a large subset of all BSP algorithms while avoiding complex message-passing programming. It allows automatic load balancing and like all BSP-inspired systems, predictable, portable and scalable performance.
