two ways to get cpu cores

gistfile1.txt

#include <thread>
#include <iostream>
#include <unistd.h>
using std::cout;
using std::endl;

int main()
{
  cout << std::thread::hardware_concurrency() << endl;
  cout << sysconf(_SC_NPROCESSORS_ONLN) << endl;
  return 0;
}