[dr. F.I.N.]

Не быстрее Round, но быстрее Trunc.

Код:

function Trunc_Dbl(Value: Double): Integer;
var
  d_w: array[0..3] of word absolute Value;
begin
  Result := ((d_w[3] shl 11) or (d_w[2] shr 5) or $8000) shr (14 - (d_w[3] shr 4 and $03FF));
end;

function Trunc_Asm(Value: Double): Integer;
const
  Half: double = 0.5;
begin
  asm
        fld     Value
        fsub    Half
        fistp   Result
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  I: Integer;
  tc1, tc2, tc3, tc4: Cardinal;
  _value: Double;
  _result: Integer;
begin
  _value := 100.56;
  tc1 := GetTickCount;
  for I := 0 to $FFFFFF do
  begin
    _result := Trunc(_value);
    if _result = 99 then
      ;
  end;
  tc1 := GetTickCount - tc1;
  //-------------
  tc2 := GetTickCount;
  for I := 0 to $FFFFFF do
  begin
    _result := Trunc_Asm(_value);
    if _result = 99 then
      ;
  end;
  tc2 := GetTickCount - tc2;
  //-------------
  tc3 := GetTickCount;
  for I := 0 to $FFFFFF do
  begin
    _result := Trunc_Dbl(_value);
    if _result = 99 then
      ;
  end;
  tc3 := GetTickCount - tc3;
  //-------------
  tc4 := GetTickCount;
  for I := 0 to $FFFFFF do
  begin
    _result := Round(_value);
    if _result = 99 then
      ;
  end;
  tc4 := GetTickCount - tc4;
  //-------------
  ShowMessageFmt('Trunc: %d'#13'Trunc_Asm: %d'#13'Trunc_Dbl: %d'#13'Round: %d', [tc1, tc2, tc3, tc4]);
end;