Is there a performance difference between i++ and ++i in C++ program?

The effective result of i++ and ++i are same. The only difference is that the i++ increases the value of i after assigning it, and for ++i, it increases the value first, then assigns its value. We can see the difference in the following code.

Example Code

using namespace std;
int main() {
   int x = 3, y, z;
   y = x++;
   z = ++x;
   cout << x << ", " << y << ", " << z;
   return 0;


5, 3, 5

Now, the question comes, that as they are doing the same task but in different order, then is there any performance issue or both are same?

Well, the performance of these operations highly dependent on the underlying architecture. One is incrementing value that is stored in the memory, it means the Von-Neumann bottleneck is basically the limiting factor in both cases.

Though we can say that the ++i is slightly faster than i++. The i++ takes local copy of the value of i before incrementing, while ++i never does. Sometimes some compiler optimizes the code if possible. But that optimization is not always being effective, or not all compiler does this thing.

Updated on: 30-Jul-2019

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