mc.erl

-module(mc).
-compile(export_all).

pmap(Fun, Lst) ->
	% get current Pid
	Self = self(), 
	
	% get a unique idendifier
	Ref  = erlang:make_ref(), 
	
	% create a process for every element in the list
	% and run do_fun on them
	Pids = lists:map(fun (X) -> 
								spawn(fun() -> do_fun(Self, Ref, Fun, X) end) 
						  end, Lst),
	
	% receive data and construct function
	gather(Pids, Ref).


do_fun(Sender, Ref, Fun, X) ->
	% run Fun, and catch error if Fun aborts
	Sender ! {self(), Ref, (catch Fun(X))}.


gather([], _) -> [];
gather([Pid | T], Ref) ->
	% gather the results in order and recursively 
	receive
		{Pid, Ref, Result} -> [Result | gather(T, Ref)]
	end.


fib(0) -> 0;
fib(1) -> 1;
fib(N) when N > 0 -> fib(N - 1) + fib(N - 2).


test() ->
	Lst = lists:duplicate(100, 27),
	{Time1, Result1} = timer:tc(lists, map, [fun fib/1, Lst]),
	{Time2, Result2} = timer:tc(?MODULE, pmap, [fun fib/1, Lst]),
	io:format("Results are equal: ~w, speedup = ~w~n", [Result1 == Result2, Time1 / Time2]).