# include <cstdlib>
# include <iostream>
# include <iomanip>
# include <ctime>
# include <omp.h>

using namespace std;

int main ( int argc, char *argv[] );

//****************************************************************************80

int main ( int argc, char *argv[] )

//****************************************************************************80
//
//  Purpose:
//
//    HELLO has each thread print out its ID.
//
//  Discussion:
//
//    HELLO is a "Hello, World" program for OpenMP.
//
//    But we demonstrate a few simple features of OpenMP, including:
//
//    How you get the "include" file.
//    How you measure wall clock time.
//    How you find out how many processors are available.
//    How you find out which thread you are in a parallel section.
//    How you find out how many threads are available in a parallel section.
//    How you set the number of threads.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    20 July 2008
//
//  Author:
//
//    John Burkardt
//
{
  int id;
  int proc_num;
  int thread_num;
  double wtime;
  double wtime1;
  double wtime2;

  cout << "\n";
  cout << "HELLO\n";
  cout << "  C++/OpenMP version\n";

  wtime1 = omp_get_wtime ( );
//
//  How many processors are available?
//
  proc_num = omp_get_num_procs ( );

  cout << "\n";
  cout << "  The number of processors available:\n";
  cout << "  OMP_GET_NUM_PROCS () = " << proc_num << "\n";
//
//  How many threads are available by default or environment setting?
//
#pragma omp parallel private ( id )
  {
    id = omp_get_thread_num ( );
    thread_num = omp_get_num_threads ( );

    if ( id == 0 )
    {
      cout << "\n";
      cout << "  Calling OMP_GET_NUM_THREADS inside a\n";
      cout << "  parallel region, we get the number of\n";
      cout << "  threads is " << thread_num << "\n";
    }
    cout << "  This is process " << id << " out of " << thread_num << "\n";
  }
//
//  Request double the number of threads.
//
  thread_num = 2 * thread_num;

  cout << "\n";
  cout << "  We request " << thread_num << " threads.\n";

  omp_set_num_threads ( thread_num );
//
//  Now how many threads do we see?
//
#pragma omp parallel private ( id )
  {
    id = omp_get_thread_num ( );
    thread_num = omp_get_num_threads ( );

    if ( id == 0 )
    {
      cout << "\n";
      cout << "  Calling OMP_GET_NUM_THREADS inside a\n";
      cout << "  parallel region, we get the number of\n";
      cout << "  threads is " << thread_num << "\n";
    }
    cout << "  This is process " << id << " out of " << thread_num << "\n";
  }
//
//  Finish up by measuring the elapsed time.
//
  wtime2 = omp_get_wtime ( );
  wtime = wtime2 - wtime1;

  cout << "\n";
  cout << "HELLO\n";
  cout << "  Normal end of execution.\n";

  cout << "\n";
  cout << "  Elapsed wall clock time = " << wtime << "\n";

  return 0;
}