using std::chrono to time a function, fully inlined

chrono-timing.cc

#include <chrono>
#include <utility>

//------------------------------------------------------------------------------

using Elapsed = double;

template<typename FN, typename ...ARGS>
inline std::pair<Elapsed, std::result_of_t<FN&&(ARGS&&...)>>
time1(
  FN&& fn, 
  ARGS&&... args)
{
  auto const start = std::chrono::high_resolution_clock::now();
  auto const result = fn(std::forward<ARGS>(args)...);
  auto const end = std::chrono::high_resolution_clock::now();
  return {std::chrono::duration<Elapsed>(end - start).count(), result};
}


//------------------------------------------------------------------------------

template<typename T>
T
dot(
  size_t const num,
  T const* const arg0,
  T const* const arg1)
{
  T result = 0;
  for (size_t i = 0; i < num; ++i)
    result += arg0[i] * arg1[i];
  return result;
}


//------------------------------------------------------------------------------

#include <iostream>
#include <unistd.h>

int
main()
{
  size_t const num = 1024 * 1024;
  double* const arr0 = new double[num];
  double* const arr1 = new double[num];
  for (size_t i = 0; i < num; ++i) {
    arr0[i] = i + 1;
    arr1[i] = 1.0 / (i + 1);
  }

  auto const result = time1(dot<double>, num, arr0, arr1);
  std::cout << "result=" << result.second << "\n"
            << "timing=" << result.first << std::endl;

  return EXIT_SUCCESS;
}