Coordinating Heterogeneous Parallel Systems with Skeletons and Activity Graphs

Large scale parallel programming projects may become heterogeneous in bothlanguage and architectural model. We propose that skeletal programmingtechniques can alleviate some of the costs involved in designing and portingsuch programs, illustrating our approach with a simple program which combinesshared memory and message passing code. We introduce Activity Graphs as asimple and practical means of capturing model independent aspects of theoperational semantics of skeletal parallel programs. They are independent oflow level details of parallel implementation and so can act as an intermediatelayer for compilation to diverse underlying models. Activity graphs providea notion of parallel activities, dependencies between activities, and theprocess groupings within which these take place. The compilation processuses a set of graph generators (templates) to derive the activity graph. Wedescribe simple schemes for transforming activity graphs into message passingprograms, targeting both MPI and BSP.