gistfile1.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <chrono>

template<typename T>
T sum_for_each(std::vector<T> const& vec)
{
  T sum = 0;
  std::for_each(vec.begin(), vec.end(),
           [&sum](int const& n) { sum += n; });
  return sum;
}

template<typename T>
T sum_forloop(std::vector<T> const& vec)
{
  T sum = 0;
  size_t const size = vec.size();
  for (size_t i=0; i<size; ++i)
    sum += vec[i];
  return sum;
}

template<typename T>
T sum_accumulate(std::vector<T> const& vec)
{
  return std::accumulate(vec.begin(), vec.end(), 0);
}

int main()
{
  using namespace std::chrono;
  
  std::vector<double> vec(6.2e7);

  high_resolution_clock::time_point t1 = high_resolution_clock::now();
  auto sum1 = sum_forloop(vec);
  high_resolution_clock::time_point t2 = high_resolution_clock::now();
  size_t duration = duration_cast<microseconds>( t2 - t1 ).count();
  std::cout << "forloop " << duration << std::endl;

  
  t1 = high_resolution_clock::now();
  auto sum2 = sum_for_each(vec);
  t2 = high_resolution_clock::now();
  duration = duration_cast<microseconds>( t2 - t1 ).count();
  std::cout << "for_each " << duration << std::endl;  
  

  t1 = high_resolution_clock::now();
  auto sum3 = sum_accumulate(vec);
  t2 = high_resolution_clock::now();
  duration = duration_cast<microseconds>( t2 - t1 ).count();
  std::cout << "accumulate " << duration << std::endl;  
  
  std::cout << sum1 << sum2 << sum3 <<std::endl;
  
  
 return 0; 
}