New example in ocamerl lib of erlocaml project: a tiny map-reduce-like (1) word-count program (word-count is the simple example often used to illustrate map-reduce principle).

First part of this example is an ocaml distributed erlang node [l52]. It is composed of one permanent registered (‘wc’) mbox [l40] which upon request create other mboxes implementing the mappers [l19] (on request, a mapper read a text file [l8] and send it word by word to reducer [l29]).

Second part of this map-reduce example is an erlang module implementing two functionalities. One of them is the reduce part implementation [l34] done by a process which accept messages from mappers and update a dictionary accordingly.
Second responsibility of this module is orchestration of the map-reduce flow [l90], consisting of running all mappers [l66], waiting end of all those executions [l79], and collecting result of all reducers [l95].

Assuming EPMD is running, this script run an ocaml node and an erlang node, and run a simple map-reduce to count words in two test files.

As usual, not sure it’s a useful example, but it was sure fun to write 🙂

(1) this is not a map-reduce lib … there is no failure case taken care of, processes pipe is mostly done through messages over network (while map-reduce is mainly meant to use an efficient filesystem based communication), etc!

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