A Proposal for OpenMP for Java

Abstract. The current OpenMP 2.5 specification does not include a binding for the Java programming language. However, Java is a wide-spread programming language that is even used for HPC programming. We propose an adaptation of OpenMP to Java by retrofitting the basic OpenMP directives to Java and further propose some new concepts to make OpenMP fit into Java’s language philosophy. We discuss how Java’s memory model matches OpenMP’s memory model and how the OpenMP bindings for Java and C++ differ. We also suggest how to achieve flexibility of an OpenMP implementation by allowing both Java threads (java.lang.Thread) and Java tasks (java.util.concurrent.FutureTask). Support for object-orientation is added to allow OpenMP to better fit to Java. For example, we suggest a parallel for-each loop over Java collections, OO-based reductions, and object-cloning semantics to adapt data-sharing clauses to Java. Also, we suggest a minimal runtime library to allow object-pooling to circumvent any implicit synchronization involved in object allocations. Finally, we present some performance numbers for a reference implementation in a research compiler.