i++ less efficient than ++i, how to show this?

Question

I am trying to show by example that the prefix increment is more efficient than the postfix increment.

In theory this makes sense: i++ needs to be able to return the

Answer 1

In response to Mihail, this is a somewhat more portable version his code:

#include 
#include 
using namespace std;

#define SOME_BIG_CONSTANT 100000000
#define OUTER 40
int main( int argc, char * argv[] ) {

    int d = 0;
    time_t now = time(0);
    if ( argc == 1 ) {
        for ( int n = 0; n < OUTER; n++ ) {
            int i = 0;
            while(i < SOME_BIG_CONSTANT) {
                d += i++;
            }
        }
    }
    else {
        for ( int n = 0; n < OUTER; n++ ) {
            int i = 0;
            while(i < SOME_BIG_CONSTANT) {
                d += ++i;
            }
        }
    }
    int t = time(0) - now;  
    printf( "%d\n", t );
    return d % 2;
}

The outer loops are there to allow me to fiddle the timings to get something suitable on my platform.

I don't use VC++ any more, so i compiled it (on Windows) with:

g++ -O3 t.cpp

I then ran it by alternating:

a.exe   

and

a.exe 1

My timing results were approximately the same for both cases. Sometimes one version would be faster by up to 20% and sometimes the other. This I would guess is due to other processes running on my system.