parallel copy

gistfile1.txt

#include <vector>
#include <thread>

void do_parallel (size_t n)
{
  std::vector<int> a (n), b (n);
 
  double c = clock ();
  std::vector<std::thread> threads;
  int total_threads = std::thread::hardware_concurrency ();
  for (int i  = 0; i < total_threads; i++)
      threads.emplace_back ([&, i]
      {
         size_t start = i * n / total_threads;
         size_t end  = (i + 1) * n / total_threads;
         std::copy (a.begin () + start, a.begin () + end, b.begin () + start);
      });
      
   for (auto &thr : threads)
       thr.join ();

   printf ("parallel time = %lf\n", (clock () - c) / CLOCKS_PER_SEC);
}

void do_serial (size_t n)
{
  std::vector<int> a (n), b (n);
 
  double c = clock ();
  std::copy (a.begin (), a.end (), b.begin ());  
  printf ("serial time = %lf\n", (clock () - c) / CLOCKS_PER_SEC);
}

int main (int argc, char **argv)
{
  if (argc < 2) return 0;
  int n;
  sscanf (argv[1], "%d", &n);
  
  do_serial (n);
  do_parallel (n);
  return 0;
}