Map, Reduce and MapReduce, the skeleton way

Composition of Map and Reduce algorithmic skeletons have been widely studied at the end of the last century and it has demonstrated effective on a wide class of problems. We recall the theoretical results motivating the introduction of these skeletons, then we discuss an experiment implementing three algorithmic skeletons, a map, a reduce and an optimized composition of a map followed by a reduce skeleton (map+reduce). The map+reduce skeleton implemented computes the same kind of problems computed by Google MapReduce, but the data flow through the skeleton is streamed rather than relying on already distributed (and possibly quite large) data items. We discuss the implementation of the three skeletons on top of ProActive/GCM in the MareMare prototype and we present some experimental obtained on a COTS cluster