source code
% The Computer Language Benchmarks Game
% https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
%% Contributed by Johan Karlsson based on Fredrik Svahn's mandelbrot program
%% Added usage of port_command by Johan Karlsson
-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),
%% Start a printing process that prints using
%% port_command to decrease memory usage
PrintProc = print_start(),
print(PrintProc,["P4\n", Arg, " ", Arg, "\n"]),
%% Spawn one process per row
Row = fun(NextProc,Y)-> row(PrintProc, NextProc, N-1, 0, ?SI+Y*2/N, N, 0, [], 7) end,
spawn_proc_chain(PrintProc,Row, N).
%% A function that spawns a chain of processes.
spawn_proc_chain(PrintProc,Row, N) ->
Spawn = fun(PP,S,F,I,NN) -> spawn(fun() -> do_spawn_proc_chain(PP,S,F,I,NN) end) end,
Spawn(PrintProc,Spawn,Row,first,N).
do_spawn_proc_chain(PrintProc,_,_,Max,Max) ->
receive done -> ok end,
%% Needed in order to let the print proccess finish printing.
print_stop(PrintProc),
halt(0);
do_spawn_proc_chain(PP,Spawn,Row,first,Max) ->
NextProc = Spawn(PP,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(PP,Spawn,Row,N,Max) ->
NextProc = Spawn(PP,Spawn,Row,N+1,Max),
Row(NextProc,N).
%% Iterate over a row, collect bits, bytes and finally print the row
row(PrintProc, 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,
print(PrintProc, Char),
NextProc ! done;
row(PP, NP,M,X, Y2, N, Bits, Bytes, 0) ->
row(PP, NP,M,X+1, Y2, N, 0, [Bits bsl 1 + m(?ITER, ?SR+(X+X)/N, Y2) | Bytes], 7);
row(PP, NP,M,X, Y2, N, Bits, Bytes, BitC) ->
row(PP, 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.
%% Print stuff
print(PP,Char) ->
PP ! Char.
print_start() ->
spawn(fun() -> do_print_start() end).
print_stop(PrintProc) ->
PrintProc ! {self(),stop},
receive stopped -> ok end.
do_print_start() ->
Fd = open_port({fd,0,1}, [out]),
print_loop(Fd).
print_loop(Fd) ->
receive {Pid,stop} ->
Pid ! stopped;
Char ->
port_command(Fd, Char), print_loop(Fd)
end.