迭代二维数组的嵌套循环的顺序更有效率 [英] Which ordering of nested loops for iterating over a 2D array is more efficient

问题描述

在时间（缓存性能）方面，以下哪个嵌套循环顺序迭代二维数组更有效？为什么？

  int a [100] [100]; （j = 0; j <100; j ++）
 {
a（$ i $ 0; i <100; i ++）
 {
 
 
 [i] [j] = 10; 
 
 
 code 
 
 
 
 
 
 
 
 
 
 
 
 
 
对于（j = 0; j <100; j ++）$ b $（i = 0; i <100; i ++）
 {
），$ b 
  b {
a [j] [i] = 10; 
 
 
 $ / code $ / pre 
 
解决方案
第一种方法稍微好一点，因为细胞被分配到彼此相邻。 
 
 
第一种方法：
 
 <$ 
 ^第一作业
 ^第二作业
 [] [] [] [] [] [code> [] [] [] []第二种方法：$ {
 $ 101 
 $ / code $ $ $ $ $ $ 
 
 
  [] [] [] [] ...] 
 ^第一作业
 ^第101作业
 [] [] [] [] [] ... 
 ^第二作业
  
 
Which of the following orderings of nested loops to iterate over a 2D array is more efficient in terms of time (cache performance)? Why?
int a[100][100];

for(i=0; i<100; i++)
{
   for(j=0; j<100; j++)
   {
       a[i][j] = 10;    
   }
}
or
for(i=0; i<100; i++)
{
   for(j=0; j<100; j++)
   {
      a[j][i] = 10;    
   }
}

解决方案
The first method is slightly better, as the cells being assigned to lays next to each other.

First method:
[ ][ ][ ][ ][ ] ....
^1st assignment
   ^2nd assignment
[ ][ ][ ][ ][ ] ....
^101st assignment
Second method:
[ ][ ][ ][ ][ ] ....
^1st assignment
   ^101st assignment
[ ][ ][ ][ ][ ] ....
^2nd assignment


                        
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