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

using namespace std;

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

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

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

//****************************************************************************80
//
//  Purpose:
//
//    MAIN is the main program for HELLO_MPI.
//
//  Discussion:
//
//    This is a simple MPI test program.
//    Each process prints out a "Hello, world!" message.
//    The master process also prints out a short message.
//
//    Modified to use the C MPI bindings, 14 June 2016.
//
//  Licensing:
//
//    This code is distributed under the MIT license. 
//
//  Modified:
//
//    14 June 2016
//
//  Author:
//
//    John Burkardt
//
//  Reference:
//
//    William Gropp, Ewing Lusk, Anthony Skjellum,
//    Using MPI: Portable Parallel Programming with the
//    Message-Passing Interface,
//    Second Edition,
//    MIT Press, 1999,
//    ISBN: 0262571323,
//    LC: QA76.642.G76.
//
{
  int id;
  int ierr;
  int p;
  double wtime;
//
//  Initialize MPI.
//
  ierr = MPI_Init ( &argc, &argv );

  if ( ierr != 0 )
  {
    cout << "\n";
    cout << "HELLO_MPI - Fatal error!\n";
    cout << "  MPI_Init returned nonzero ierr.\n";
    exit ( 1 );
  }
//
//  Get the number of processes.
//
  ierr = MPI_Comm_size ( MPI_COMM_WORLD, &p );
//
//  Get the individual process ID.
//
  ierr = MPI_Comm_rank ( MPI_COMM_WORLD, &id );
//
//  Process 0 prints an introductory message.
//
  if ( id == 0 ) 
  {
    timestamp ( );
    cout << "\n";
    cout << "P" << id << ":  HELLO_MPI - Master process:\n";
    cout << "P" << id << ":    C++/MPI version\n";
    cout << "P" << id << ":    An MPI example program.\n";
    cout << "\n";
    cout << "P" << id << ":    The number of processes is " << p << "\n";
    cout << "\n";
  }
//
//  Every process prints a hello.
//
  if ( id == 0 ) 
  {
    wtime = MPI_Wtime ( );
  }
  cout << "P" << id << ":    'Hello, world!'\n";
//
//  Process 0 says goodbye.
//
  if ( id == 0 )
  {
    wtime = MPI_Wtime ( ) - wtime;
    cout << "P" << id << ":    Elapsed wall clock time = " << wtime << " seconds.\n";
  }
//
//  Terminate MPI.
//
  MPI_Finalize ( );
//
//  Terminate.
//
  if ( id == 0 )
  {
    cout << "\n";
    cout << "P" << id << ":  HELLO_MPI:\n";
    cout << "P" << id << ":    Normal end of execution.\n";
    cout << "\n";
    timestamp ( );
  }
  return 0;
}
//****************************************************************************80

void timestamp ( )

//****************************************************************************80
//
//  Purpose:
//
//    TIMESTAMP prints the current YMDHMS date as a time stamp.
//
//  Example:
//
//    31 May 2001 09:45:54 AM
//
//  Licensing:
//
//    This code is distributed under the MIT license. 
//
//  Modified:
//
//    08 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    None
//
{
# define TIME_SIZE 40

  static char time_buffer[TIME_SIZE];
  const struct std::tm *tm_ptr;
  std::time_t now;

  now = std::time ( NULL );
  tm_ptr = std::localtime ( &now );

  std::strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm_ptr );

  std::cout << time_buffer << "\n";

  return;
# undef TIME_SIZE
}