横向遍历比纵向遍历更高效

Posted 2022-09-11 zyf-yxm

public void testtt() 
        int[][] array = new int[64 * 1024][1024];

     // 横向遍历
     long currentTimeMillis = System.currentTimeMillis();
     for(int i = 0; i < 64 * 1024; i ++)
         for(int j = 0; j < 1024; j ++)
             array[i][j] ++;
     
     System.out.println(System.currentTimeMillis()-currentTimeMillis);

     // 纵向遍历
     currentTimeMillis = System.currentTimeMillis();
     for(int i = 0; i < 1024; i ++)
         for(int j = 0; j < 64 * 1024; j ++)
             array[j][i] ++;
     System.out.println(System.currentTimeMillis()-currentTimeMillis);
    

 

 这里涉及到cpu cache命中率的问题,横向遍历的命中率大于纵向遍历

附详细地址:https://blog.csdn.net/u010983881/article/details/82704733