这是Java中整数数组中更昂贵的操作交换或比较

Question

Which is more expensive operation swap or comparison in integer array in Java ? Or they can all be thought as same ?

Context: Sorting for an almost sorted array (I am not talking about k-sorted array where each element is displaced from the right position by at most k). Even if we use insertion sort, number of comparisons by the end will be same as they would have been for any array or for worst case. Isn't it ? It is just that swaps will be fewer. Please correct if I am wrong.

Answer 1

Swap should be more expensive because it includes:

1. Reading data from memory to cache
2. Reading data from cache to registers
3. Writing data back to cache

Comparison should be less expensive because it includes:

1. Reading data from memory to cache
2. Reading data from cache to registers
3. Executing single compare operations on two registers (which should be a little faster than writing two integers into a cache)

But modern processors are complex and different from each other, so the best way to get the right answer is to benchmark your code.