#include <array>
#include <chrono>
#include <cstdlib>
#include <ctime>
#include <iostream>

using namespace std::chrono;
using namespace std;

int
    main ()
{
    // Setup
    int sum = 0;
    const std::size_t arrLength = 4000 + 4000 * 4000;
    std::array<int, arrLength> arr;

    for ( size_t i = 0; i < arrLength; i++ ) {
    int value = rand () % arrLength;
    arr[i] = value;
    }

    // Start timer
    auto start = high_resolution_clock::now ();

    // Algo
    for ( int x = 0; x < 4000; ++x ) {
    for ( int y = 0; y < 4000; ++y ) {
        sum += arr[x * 4000 + y];
    }
    }

    // Stop timer and count duration
    auto stop = high_resolution_clock::now ();
    auto duration = duration_cast<microseconds> (stop - start);

    cout << "Finished after" << duration.count () << endl;

    // Start timer
    start = high_resolution_clock::now ();

    // Algo
    for ( int y = 0; y < 4000; ++y ) {
    for ( int x = 0; x < 4000; ++x ) {
        sum += arr[x + 4000 * y];
    }
    }

    // Stop timer and count duration
    stop = high_resolution_clock::now ();
    duration = duration_cast<microseconds> (stop - start);

    cout << "Finished after" << duration.count () << endl;

    return 0;
}