variable swap comparison

#include <iostream>
#include <sys/time.h>                // for gettimeofday()

// g++ main.cpp -o swap_test -march=native -O2

using namespace std;

#define NUMSTEPS 1000000000

int main(){
    timeval t1, t2, t3, t4;
    unsigned int a = 32, b = 64, c = 0, i = 0;
    double elapsedTime;

    gettimeofday(&t1, NULL);
    for(i = 0; i < NUMSTEPS; ++i){
        swap(a, b);
    }

    gettimeofday(&t2, NULL);
    for(i = 0; i < NUMSTEPS; ++i){
        a^=b;
        b^=a;
        a^=b;
    }

    gettimeofday(&t3, NULL);
    for(i = 0; i < NUMSTEPS; ++i){
        c = b;
        b = a;
        a = c;
    }
    gettimeofday(&t4, NULL);

    // compute and print the elapsed time in millisec
    elapsedTime = (t2.tv_sec - t1.tv_sec) * 1000.0;      // sec to ms
    elapsedTime += (t2.tv_usec - t1.tv_usec) / 1000.0;   // us to ms
    cout << "swap\t" << elapsedTime << " ms.\n";

    elapsedTime = (t3.tv_sec - t2.tv_sec) * 1000.0;      // sec to ms
    elapsedTime += (t3.tv_usec - t2.tv_usec) / 1000.0;   // us to ms
    cout << "XOR\t" << elapsedTime << " ms.\n";

    elapsedTime = (t4.tv_sec - t3.tv_sec) * 1000.0;      // sec to ms
    elapsedTime += (t4.tv_usec - t3.tv_usec) / 1000.0;   // us to ms
    cout << "+var\t" << elapsedTime << " ms.\n";
    cout<<a<<b<<c<<"\b\b\b\b\b\b";
    return 0;
}