The Computer Language
24.04 Benchmarks Game

mandelbrot Erlang program

source code

% The Computer Language Benchmarks Game
% https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
%% Contributed by Fredrik Svahn based on Per Gustafsson'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(Y)-> spawn(fun()-> row(0, ?SI+Y*2/N, N, 0, [], 7) end) 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 -> halt(0) 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 ->
	    put_chars(Bits, Bytes, BitC),
	    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.

put_chars(_, Bytes, 7)-> io:put_chars(lists:reverse(Bytes));
put_chars(Bits, Bytes, C) -> io:put_chars(lists:reverse([Bits bsl (C+1) | Bytes])).
    

notes, command-line, and program output

NOTES:
64-bit Ubuntu quad core
Erlang/OTP 27 [erts-15.0]
[source] [64-bit] [smp:4:4]
[ds:4:4:10] [async-threads:1] [jit:ns]



 Mon, 20 May 2024 22:46:51 GMT

MAKE:
mv mandelbrot.erlang mandelbrot.erl
/opt/src/otp_src_27.0/bin/erlc mandelbrot.erl
rm mandelbrot.erl

1.05s to complete and log all make actions

COMMAND LINE:
 /opt/src/otp_src_27.0/bin/erl -smp enable -noshell -run  mandelbrot main 1000

UNEXPECTED OUTPUT 

_out 1000_out differ: byte 855, line 3

(BINARY) PROGRAM OUTPUT NOT SHOWN