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2008 / 12 / 22 ( Mon )

¡ÖÉÔÊÑ¥¯¥é¥¹¤È¤·¤ÆÀß·×¤·¤¿Ê£ÁÇ¿ô¥¯¥é¥¹Complex¡ÊJava¤Ë¤è¤ë¼ÂÁõ¡Ë¡×¤ËÂÐ¤·¤Æ¡¢

¡ädiv()¤Ë¤ª¤¤¤Æ¡¢¤¢¤é¤«¤¸¤áÊ¬Êì(c.re*c.re + c.im*c.im)¤ò·×»»¤·¤Æ°ì»þÊÑ¿ôdenominator¤Ë³ÊÇ¼¤·¤Æ¤¤¤ë¤Î¤Ï¡¢¤³¤Î·×»»¤ò2ÅÙ¹Ô¤¦¤È¥Ñ¥Õ¥©¡¼¥Þ¥ó¥¹¤¬Äã²¼¤¹¤ë¤¿¤á¤Ç¤¹¡£¤³¤Î¤è¤¦¤Ë¡¢Ê£¿ô²ó¥ª¥Ö¥¸¥§¥¯¥È¤ò»²¾È¤¹¤ë¾ì¹ç¤Ï¤½¤ÎÃÍ¤ò°ì»þÊÑ¿ô¤Ë³ÊÇ¼¤¹¤ë¤³¤È¤Ç¥Ñ¥Õ¥©¡¼¥Þ¥ó¥¹¤¬¸þ¾å¤·¤Þ¤¹¡£

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Complex¥¯¥é¥¹¤Ë¿·¤¿¤Ë¥á¥½¥Ã¥Énaive_div()¤òÄÉ²Ã¤¹¤ë¤È¤È¤â¤Ë¡¢Complex¤ÎÆâÉô¥¯¥é¥¹¤È¤·¤Æ¥Æ¥¹¥ÈÍÑ¤Î¥¯¥é¥¹ComplexPerformanceTest¤ò¼ÂÁõ¤·¤Þ¤·¤¿¡£¤³¤ì¤ò5²ó¼Â¹Ô¤·¡¢¼¡¤Ë c1.naive_div(c2); ¤ò c1.div(c2); ¤Ë½ñ¤´¹¤¨¤Æ5²ó¼Â¹Ô¤·¡¢¤½¤ì¤¾¤ì¤Î¼Â¹Ô»þ´Ö¤ò·×Â¬¤¹¤ë¤³¤È¤Ç¥Ñ¥Õ¥©¡¼¥Þ¥ó¥¹¤ÎÈæ³Ó¤ò¹Ô¤¤¤Þ¤·¤¿¡£

¥á¥½¥Ã¥Énaive_div()

/* ¤³¤Á¤é¤ÎÊý¤¬ÃÙ¤¤¤ÈÍ½Â¬¤µ¤ì¤ë¡£*/
public Complex naive_div(Complex c) {
  return new Complex(
    (re*c.re + im*c.im)/(c.re*c.re + c.im*c.im),
    (im*c.re - re*c.im)/(c.re*c.re + c.im*c.im));
}

¥á¥½¥Ã¥Édiv()

/* ¤³¤Á¤é¤ÎÊý¤¬Â®¤¤¤ÈÍ½Â¬¤µ¤ì¤ë¡£*/
public Complex div(Complex c) {
  double denominator = c.re*c.re + c.im*c.im;
  return new Complex((re*c.re + im*c.im)/denominator,
    (im*c.re - re*c.im)/denominator);
}

¥Æ¥¹¥ÈÍÑ¤Î¥¯¥é¥¹

class ComplexPerformanceTest {
  
  public static void main(String args[]) {
    long start[] = new long[100];
    long stop[] = new long[100];
    long time[] = new long[100];
    
    for(int j=0; j<100; j++) {
      start[j] = System.currentTimeMillis();
      for(int i=0; i<1000000; i++) {
        Complex c1 = new Complex(1, 2);
        Complex c2 = new Complex(3, 4);
        c1.naive_div(c2);
      }
      stop[j] = System.currentTimeMillis();
    }
    for(int i=0; i<start.length; i++) {
      time[i] = stop[i] - start[i];
    }
    System.out.println(mean(time));
  }
  
  private static long mean(long l[]) {
    long sum = 0;
    for(int i=0; i<l.length; i++) {
      sum += l[i];
    }
    return sum/l.length;
  }
}