Concrete data structures and functional parallel programming

We present a framework for designing parallel programming languages whose semantics is functional and where communications are explicit. To this end, we specialize Brookes and Geva's generalized concrete data structures with a notion of explicit data layout and obtain a CCC of distributed structures called arrays. We nd that arrays' symmetric replicated structures, suggested by the data-parallel SPMD paradigm, are incompatible with sum types. We then outline a functional language with explicitly-distributed (monomorphic) concrete types, including higher-order, sum and recursive ones. In this language, programs can be as large as the network and can observe communication events in other programs. Such exibility is missing from current data-parallel languages and amounts to a fusion with their so-called annotations, directives or metalanguages. 1 Explicit communications and functional programming Faced with the mismatch between parallel programming languages and the requirements of their users, researchers are advocating resource-aware programming tools 9] and programs with measurable utilization of network capacity 19], 17] where control parallelism can be mixed with data parallelism. In this article we propose semantic models for languages whose programs are explicitly parallel and whose semantics is functional. Such languages are expected to address the above-stated requirements by (i) expressing data placement, and hence communications explicitly, ?