# include <mpi.h>
# include <stdio.h>
# include <stdlib.h>
# include <time.h>

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

/******************************************************************************/

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

/******************************************************************************/
/*
  Purpose:

    MAIN is the main program for BONES.

  Discussion:

    BONES is a simple demonstration of the use of MPI by a C program.

    This program should be run on at least two processes.
    Any processes beyond the first two will not be given any work.

  Licensing:

    This code is distributed under the GNU LGPL license. 

  Modified:

    11 October 2007

  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.
*/
{
  int count;
  float data[100];
  int dest;
  int i;
  int ierr;
  int num_procs;
  int rank;
  MPI_Status status;
  int tag;
  float value[200];
/*
  Initialize MPI.
*/
  ierr = MPI_Init ( &argc, &argv );

  if ( ierr != 0 )
  {
    printf ( "\n" );
    printf ( "BONES_MPI - Fatal error!\n" );
    printf ( "  MPI_Init returns nonzero IERR.\n" );
    exit ( 1 );
  }
/*
  Determine this process's rank.
*/
  ierr = MPI_Comm_rank ( MPI_COMM_WORLD, &rank );
/*
  Determine the number of available processes.
*/
  ierr = MPI_Comm_size ( MPI_COMM_WORLD, &num_procs );
/*
  Have Process 0 say hello.
*/
  if ( rank == 0 )
  {
    timestamp ( );
    printf ( "\n" );
    printf ( "BONES_MPI:\n" );
    printf ( "  C version\n" );
    printf ( "  An MPI example program.\n" );
    printf ( "  The number of processes available is %d\n", num_procs );
  }
/*
  Process 0 expects up to 200 real values, from any source.
*/
  if ( rank == 0 ) 
  {
    tag = 55;

    ierr = MPI_Recv ( value, 200, MPI_FLOAT, MPI_ANY_SOURCE, tag, 
      MPI_COMM_WORLD, &status );

    ierr = MPI_Get_count ( &status, MPI_FLOAT, &count );

    printf ( "P:%d Got %d elements.\n", rank, count );

    printf ( "P:%d value[5] = %f\n", rank, value[5] );
  }
/*
  Process 1 sends 100 real values to process 0.
*/
  else if ( rank == 1 )
  {
    printf ( "\n" );
    printf ( "P:%d - setting up data to send to process 0.\n", rank );

    for ( i = 0; i < 100; i++ ) 
    {
      data[i] = i;
    }

    dest = 0;
    tag = 55;
    ierr = MPI_Send ( data, 100, MPI_FLOAT, dest, tag, MPI_COMM_WORLD );
  }
/*
  Any other process is idle.
*/
  else
  {
    printf ( "\n" );
    printf ( "P:%d - MPI has no work for me!\n", rank );
  }
/*
  Terminate MPI.
*/
  ierr = MPI_Finalize ( );
/*
  Terminate.
*/
  if ( rank == 0 )
  {
    printf ( "\n" );
    printf ( "BONES:\n" );
    printf ( "  Normal end of execution.\n" );
    printf ( "\n" );
    timestamp ( );
  }
  return 0;
}
/******************************************************************************/

void timestamp ( )

/******************************************************************************/
/*
  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 GNU LGPL license. 

  Modified:

    24 September 2003

  Author:

    John Burkardt

  Parameters:

    None
*/
{
# define TIME_SIZE 40

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

  now = time ( NULL );
  tm = localtime ( &now );

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

  printf ( "%s\n", time_buffer );

  return;
# undef TIME_SIZE
}