mandelbrot_no_io.erl

%% The Computer Language Benchmarks Game
%% http://shootout.alioth.debian.org/
%% Contributed by Fredrik Svahn based on Per Gustafsson's mandelbrot program

-module(mandelbrot_no_io).
-export([start/0, main/1, row/6]).
-define(LIM_SQR, 4.0).
-define(ITER, 50).
-define(SR, -1.5).
-define(SI, -1).

start() -> main(64).

main(N) ->
	%% Spawn one process per row
	Row = fun(Y)-> spawn(mandelbrot_no_io, row, [ 0, ?SI+Y*2/N, N, 0, [], 7]) end,
	Pids = lists:map(Row, lists:seq(0,N-1)),

	%%Pass token around to make sure printouts are in the right order
	hd(Pids) ! tl(Pids) ++ [ self() ],
	receive _Token -> ok end.
			

%Iterate over a row, collect bits, bytes and finally print the row
row(X, _, N, Bits, Bytes, BitC) when X =:= N-1 ->
   receive Pids ->
	    hd(Pids) ! tl(Pids)
   end;

row( X, Y2, N, Bits, Bytes, 0) ->
   row( X+1, Y2, N, 0, [Bits bsl 1 + m(?ITER, ?SR+X*2/N, Y2) | Bytes], 7);

row( X, Y2, N, Bits, Bytes, BitC) ->
   row( X+1, Y2, N, Bits bsl 1 + m(?ITER, ?SR+X*2/N, Y2), Bytes, BitC-1).

%Mandelbrot algorithm
m(Iter, CR,CI) -> m(Iter - 1, CR, CI, CR, CI).

m(Iter, R, I, CR, CI) ->
   case R*R+I*I > ?LIM_SQR of 
	false when Iter > 0 -> m(Iter-1, R*R-I*I+CR, 2*R*I+CI, CR, CI);
	false -> 1;
	true -> 0
   end.