timing1.cpp

// Timing in C++14 with auto lambda parameters

#include <chrono>
#include <iostream>

// need C++14 for auto lambda parameters
auto timing = [](auto&& F, auto&&... params) {
    auto start = std::chrono::steady_clock::now();
    // execute the function
    std::forward<decltype(F)>(F)(std::forward<decltype(params)>(params)...);
    return std::chrono::duration_cast<std::chrono::milliseconds>(
               std::chrono::steady_clock::now() - start)
        .count();
};

void f(std::size_t numsteps) // we'll measure how long this function runs
{
    // need volatile, otherwise the compiler optimizes the loop
    for (volatile std::size_t i = 0; i < numsteps; ++i)
        ;
}

int main() {
    auto taken = timing(f, 500 '000' 000); // measure the time taken to run f()
    std::cout << "Took " << taken << " milliseconds" << std::endl;

    taken = timing(f, 100 '000' 000); // measure again
    std::cout << "Took " << taken << " milliseconds" << std::endl;

    std::cout << "Took " << timing([numsteps = (std::size_t)100000000] {
        for (volatile std::size_t i = 0; i < numsteps; ++i)
            ;
    }) << " milliseconds"
              << std::endl;
}