Parmap is a minimalistic library allowing to exploit multicore architecture for OCaml programs with minimal modifications: if you want to use your many cores to accelerate an operation which happens to be a map, fold or map/fold (map-reduce), just use Parmap's parmap, parfold and parmapfold primitives in place of the standard List.map and friends, and specify the number of subprocesses to use by the optional parameter ~ncores.