パフォーマンス関連

実験君１

class Num 
{
  public static char utoa (ulong u)
  {
    char tmp = new char [20];
    int i = tmp.Length;
    do {
      tmp [--i] = (char)(u % 10 + '0');
    } while ((u /= 10) > 0);

    char [] cs = new char [tmp.Length - i]; 
    Array.Copy (tmp, i, cs, 0, cs.Length);

    return cs;
  }
}

実験君２

class Num 
{
  public static StringBuilder utoa (ulong u)
  {
    StringBuilder sb = new StringBuilder (20);
    do {
      sb.Insert (0, (char)(u % 10 + '0'));
    } while ((u /= 10) > 0);

    return sb;
  }
}

実験君３

class Num 
{

  static ulong  U = new ulong  {
      1,
      10,
      100,
      1000,
      10000,
      100000,
      1000000,
      10000000,
      100000000,
      1000000000,
      10000000000,
      100000000000,
      1000000000000,
      10000000000000,
      100000000000000,
      1000000000000000,
      10000000000000000,
      100000000000000000,
      1000000000000000000,
      10000000000000000000,
  };

  public static char utoa (ulong u)
  {
    if (u == 0)
      return new char  {'0'};

    int i = 19, j = 0;

    while (u / U [i] == 0) --i;

    char [] cs = new char [i + 1];
    do {
      ulong n = u / U [i];
      cs [j++] = (char)(n + '0');
      u -= U [i--] * n;
    } while (i >= 0);

    return cs;
  }
}

これらを次のようなテストで比較。

class X 
{
  static void Main ()
  {
    char[] cs;

    DateTime t;

    t = DateTime.Now;
    for (ulong i = 0; i < 1000000; ++i)
      cs = Num.utoa (1234567890);
    Console.WriteLine (DateTime.Now - t);
  }
}

結果

n1:MS.NET - 00:00:00.7500000
n2:MS.NET - 00:00:01.6406250
n3:MS.NET - 00:00:01.3593750

n1:Mono   - 00:00:02.1250000 (90019 KB)
n2:Mono   - 00:00:02.9530000 (76348 KB)
n3:Mono   - 00:00:01.9060000 (35332 KB)

全体的にMS.NETの方が速いですが、n1,n3の結果がMS.NETとMonoで逆転していることが気になりました。Monoはメモリアロケートが不利ってことなのかなぁ。