Talk:Improving language shootout results

From Free Pascal wiki

This gives about 15% improvement on Mac OS X 10.5, fpc 2.2.4 over the present version in the shootout:

The most important tricks are conversion of the multiplication for Cx and Cy in the loops into additions, actually manually in line merging the inlined function and save some assignements there. A real boost would be to use 128 bit xmm registers and instructions for Cx, Cy, Zr, Zi, Tr, Ti as well as threads for the quad core shootout, as some of the competitors do.

program mandelbrot2;

var
  n: longint;
  TextBuf: array[0..$FFF] of byte;
  OutFile: PText;

procedure run;
const
  Limit: double = 4.0;
  two: double = 2.0;
var
  i, index1, index2, bits, bit: longint;
  Zr, Zi, Ti, Tr: double;
  Cx, Cy, Step: double;
begin
  Step := two/n;
  Cy := -1.0;
  for index1 := 1 to n do
  begin
    Cx := -1.5;
    bits := 255;
    bit  := 128;
    for index2 := 1 to n do
    begin
      Ti := Cy * Cy;
      Tr := Cx * Cx;
      if (Tr + Ti >= limit) then
        bits := bits xor bit
      else
      begin
        Zi := (Cx + Cx + 1.0) * Cy;
        Zr := Tr - Ti + Cx;
        Ti := Zi * Zi;
        Tr := Zr * Zr;
        if (Tr + Ti >= limit) then
          bits := bits xor bit
        else
        begin
          for i := 3 to 50 do
          begin
            Zi := Zr*Zi + Zr*Zi + Cy;
            Zr := Tr - Ti + Cx;
            Ti := Zi * Zi;
            Tr := Zr * Zr;
            if (Tr + Ti >= limit) then
            begin
              bits := bits xor bit;
              break;
            end;
          end;
        end;
      end;
      if bit > 1 then
        bit := bit shr 1
      else
      begin
        write(OutFile^, chr(bits));
        bits := 255;
        bit  := 128;
      end;
      Cx := Cx + Step;
    end;
    if bit < 128 then
      write(OutFile^, chr(bits xor ((bit shl 1) - 1)));
    Cy := Cy + Step;
  end;
end;
 
begin
  OutFile := @Output;
  SetTextBuf(OutFile^, TextBuf);

  Val(ParamStr(1), n);
  writeln(OutFile^, 'P4');
  writeln(OutFile^, n,' ',n);

  run;
end.