PAL: high level parallel programming with Java annotations

We present a new programming approach based on user annotations that can be used to transform plain Java programs into suitable parallel code that can be run on workstation clusters, networks and grids. The only user responsibility consists in decorating the methods that will eventually be executed in parallel with standard Java 1.5 annotations. Then these annotations are automatically processed and parallel byte code is derived. When the annotated program is started, it automatically retrieves the information about the executing platform and evaluates the information specified inside the annotations to transform the byte-code into a semantically equivalent multithreaded/multitask version. The results returned by the annotated methods, when invoked, are futures with a wait-by-necessity semantics. A PAL prototype has been implemented in Java, using JJPF as Parallel Framework. The experiments made with the prototype are encouraging: the design of parallel applications has been greatly simplified and the performances obtained are the same of an application directly written in JJPF.