A Combination of Intra- and Inter-place Work Stealing for the APGAS Library

Since today's clusters consist of nodes with multicore processors, modern parallel applications should be able to deal with shared and distributed memory simultaneously. In this paper, we present a novel hybrid work stealing scheme for the APGAS library for Java, which is a branch of the X10 project. Our scheme extends the library's runtime system, which traditionally performs intra-node work stealing with the Java Fork/Join framework. We add an inter-node work stealing scheme that is inspired by lifeline-based global load balancing. The extended functionality can be accessed from the APGAS library with new constructs. Most important, locality-flexible tasks can be submitted with asyncAny, and are then automatically scheduled over both nodes and cores. In experiments with up to 144 workers on up to 12 nodes, our system achieved near linear speedups for three benchmarks.