tiny_pmap.erl

-module(tiny_pmap).

-export([pmap/2]).

-define(CONTASKNUM, 2).

pmap(Fun, List) ->
    pmap(List, Fun, 1, [], []).

pmap([], _, _, [], ResList) ->
    ResList;
pmap([], _, _, RefList, ResList) ->
    ResList ++ lists:reverse([task:await(Ref) || Ref <- RefList]);
pmap([Head | Tail], Fun, N, RefList, ResList) ->
    {NewResList, NewRefList, NewN} = pmap_flush(ResList, RefList, N),
    pmap(Tail, Fun, NewN + 1,
         [task:async(erlang, apply, [Fun, [Head]]) | NewRefList], NewResList).

pmap_flush(ResList, RefList, N) ->
    case N rem (?CONTASKNUM + 1) of
        0 ->
            NewResList = ResList ++ lists:reverse([task:await(Ref) || Ref <- RefList]),
            {NewResList, [], 1};
        _ ->
            {ResList, RefList, N}
    end.