#include <bits/stdc++.h>

using namespace std;

void f()
{
    volatile double d = 0;
    for (int n = 0; n != 10000; ++n)
        for (int m = 0; m != 10000; ++m)
            d += d * n * m;
}

void test_clock()
{
    const std::clock_t c_start = std::clock();
    auto t_start = std::chrono::high_resolution_clock::now();
    
    std::thread t1(f);
    std::thread t2(f); // f() is called on two threads
    t1.join();
    t2.join();
    
    const std::clock_t c_end = std::clock();
    const auto t_end = std::chrono::high_resolution_clock::now();

    cout << std::fixed << std::setprecision(2)
         << "CPU time used: "
         << 1000.0 * (c_end - c_start) / CLOCKS_PER_SEC
         << "ms\n" << endl;

    auto duration = t_end - t_start;
    
    cout << "Wall clock time passed: " << duration << endl;
}

int main(void)
{
    struct timespec ts1, ts2, diff;
    clock_gettime(CLOCK_MONOTONIC_RAW, &ts1);
    cout << ts1.tv_sec << " " << ts1.tv_nsec << endl;    
    std::this_thread::sleep_for(std::chrono::microseconds(3));
    clock_gettime(CLOCK_MONOTONIC_RAW, &ts2);
    cout << ts2.tv_sec << " " << ts2.tv_nsec << endl;

    diff.tv_sec  = ts2.tv_sec  - ts1.tv_sec;
    diff.tv_nsec = ts2.tv_nsec - ts1.tv_nsec;

    cout << "   sleep_for: 3us" << endl;
    cout << " diff.tv_sec: " << diff.tv_sec << endl;
    cout << "diff.tv_nsec: " << diff.tv_nsec << endl;

    cout << "time diff(us): " << diff.tv_sec + diff.tv_nsec/1000 << endl;

    test_clock();
    
    return 0;
}