The stupidity of using XOR to swap integers

swaptest.cpp

#include <iostream>
#include <vector>
#include <random>
#include <iterator>
#include <algorithm>
#include <functional>
#include <chrono>

using test_type = unsigned;

void stupid_swap(test_type &a, test_type &b)
{
    a ^= b;
    b ^= a;
    a ^= b;
}

double timeit(std::function<void(void)> func, int rep_count = 25)
{
    std::vector<double> times;

    for(int i = 0; i < rep_count; i++) {
        auto start = std::chrono::steady_clock::now();
        func();
        auto end = std::chrono::steady_clock::now();
        times.push_back(std::chrono::duration<double, std::chrono::microseconds::period>(end - start).count());
    }
    return *min_element(begin(times), end(times));
}

int main()
{
    const size_t num_elem = 10000000;
    std::mt19937 rnd(0xdeadbeefU);
    std::uniform_int_distribution<test_type> dist;
    std::vector<test_type> data1, data2;
    std::generate_n(back_inserter(data1), num_elem, [&]() { return dist(rnd); });
    std::generate_n(back_inserter(data2), num_elem, [&]() { return dist(rnd); });

    std::cout << "stupid_swap: " << timeit([&]() {
        for(size_t i = 0; i < data1.size(); i++) {
            stupid_swap(data1[i], data2[i]);
        }
    }) << "us\n";

    std::cout << "std::swap: " << timeit([&]() {
        std::swap_ranges(begin(data1), end(data1), begin(data2));
    }) << "us\n";
}

zzz_output.txt

$ g++ -Wall -Wextra -pedantic -std=c++1y -O2 swaptest.cpp -o swaptest && ./swaptest

stupid_swap: 15855.7us
std::swap: 8926.66us