source code
% The Computer Language Benchmarks Game
% http://benchmarksgame.alioth.debian.org/
%% Contributed by Johan Karlsson based on Fredrik Svahn's mandelbrot program
-module(mandelbrot).
-export([main/1]).
-define(LIM_SQR, 4.0).
-define(ITER, 50).
-define(SR, -1.5).
-define(SI, -1).
main([Arg]) ->
N = list_to_integer(Arg),
io:put_chars(["P4\n", Arg, " ", Arg, "\n"]),
%% Spawn one process per row
Row = fun(NextProc,Y)-> row(NextProc, N-1, 0, ?SI+Y*2/N, N, 0, [], 7) end,
spawn_proc_chain(Row, N).
%% A function that spawns a chain of processes.
spawn_proc_chain(Row, N) ->
Spawn = fun(S,F,I,NN) -> spawn(fun() -> do_spawn_proc_chain(S,F,I,NN) end) end,
Spawn(Spawn,Row,first,N).
do_spawn_proc_chain(_,_,Max,Max) ->
receive _ -> halt(0) end;
do_spawn_proc_chain(Spawn,Row,first,Max) ->
NextProc = Spawn(Spawn,Row,1,Max),
%% I'm the first process in the chain. Inform my self that I can finish.
self() ! done,
%% Execute the row function
Row(NextProc,0);
do_spawn_proc_chain(Spawn,Row,N,Max) ->
NextProc = Spawn(Spawn,Row,N+1,Max),
Row(NextProc,N).
%% Iterate over a row, collect bits, bytes and finally print the row
row(NextProc,X,X, _, _, Bits, Bytes, C) ->
Char = case C of
7 -> lists:reverse(Bytes);
C -> lists:reverse([Bits bsl (C+1) | Bytes])
end,
%% Wait for the previous process to finish before printing
receive _ -> ok end,
io:put_chars(Char),
NextProc ! done;
row(NP,M,X, Y2, N, Bits, Bytes, 0) ->
row(NP,M,X+1, Y2, N, 0, [Bits bsl 1 + m(?ITER, ?SR+(X+X)/N, Y2) | Bytes], 7);
row(NP,M,X, Y2, N, Bits, Bytes, BitC) ->
row(NP,M,X+1, Y2, N, Bits bsl 1 + m(?ITER, ?SR+(X+X)/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.