measurement of CPU time using clock()

measure_cpu_time.cpp

#include <iostream>
#include <time.h>

int main() {

  clock_t start, end;

  start = clock();

  long sum = 0;
  for( long i=0; i < 1<<30; i++) {
    sum += i;
  }
  std::cout << sum << std::endl;

  end = clock();

  std::cerr << "Elapased time : " << (double)(end-start)/(CLOCKS_PER_SEC) << std::endl;
  
  return 0;
}