代码优化试验——短循环优化（下）[2]

       int i, j; timer timer;

       timer.start();

       for (i = 0; i < 5; i++) sum4();

       cout << "sum4  : " << timer.gettime() << endl;

       timer.start();

       sum4();sum4();sum4();sum4();sum4();

       cout << "sum4e : " << timer.gettime() << endl;

       timer.start();

       for (i = 0; i < 5; i++) sum5();

       cout << "sum5  : " << timer.gettime() << endl;

       timer.start();

       sum5();sum5();sum5();sum5();sum5();

       cout << "sum5e : " << timer.gettime() << endl;

       timer.start();

       for (i = 0; i < 100; i++) sum4();

       cout << "sum4h : " << timer.gettime() << endl;

       timer.start();

       for (i = 0; i < 100; i++) sum5();

       cout << "sum5h : " << timer.gettime() << endl;

       timer.start();

       for (i = 0; i < 1000; i++)

              for (j = 0; j < 5; j++) sum4();

       cout << "sum4t : " << timer.gettime() << endl;