program main

c*********************************************************************72
c
cc MAIN is the main program for HELLO.
c
c  Discussion:
c
c    HELLO is a simple MPI test program.
c
c    Each process prints out a "Hello, world!" message.
c
c    The master process also prints out a short message.
c
c  Licensing:
c
c    This code is distributed under the GNU LGPL license. 
c
c  Modified:
c
c    30 October 2008
c
c  Author:
c
c    John Burkardt
c
c  Reference:
c
c    William Gropp, Ewing Lusk, Anthony Skjellum,
c    Using MPI: Portable Parallel Programming with the
c    Message-Passing Interface,
c    Second Edition,
c    MIT Press, 1999,
c    ISBN: 0262571323,
c    LC: QA76.642.G76.
c

c
c  Define MPI symbols:
c
      include 'mpif.h'
c
c implicit none
c
      integer error
      integer id
      integer p
      double precision wtime
c
c  Initialize MPI.
c
      call MPI_Init ( error )
c
c  Get the number of processes.
c
      call MPI_Comm_size ( MPI_COMM_WORLD, p, error )
c
c  Get the individual process ID.
c
      call MPI_Comm_rank ( MPI_COMM_WORLD, id, error )
c
c  Print a message.
c
      if ( id .eq. 0 ) then

        wtime = MPI_Wtime ( )

        write ( *, '(a)' ) ' '
        write ( *, '(a)' ) 'HELLO_WORLD - Master process:'
        write ( *, '(a)' ) '  FORTRAN77 version'
        write ( *, '(a)' ) '  A simple MPI program.'
        write ( *, '(a)' ) ' '
        write ( *, '(a,i3)' ) '  The number of processes is ', p
        write ( *, '(a)' ) ' '

      end if

      write ( *, '(a)' ) ' '
      write ( *, '(a,i3,a)' ) '  Process ', id, 
     &  ' says "Hello, world!"'

      if ( id .eq. 0 ) then

        write ( *, '(a)' ) ' '
        write ( *, '(a)' ) 'HELLO_WORLD - Master process:'
        write ( *, '(a)' ) 
     &    '  Normal end of execution: "Goodbye, world!".'

        wtime = MPI_Wtime ( ) - wtime
        write ( *, '(a)' ) ' '
        write ( *, '(a,g14.6,a)' ) 
     &  'Elapsed wall clock time = ', wtime, ' seconds.'

      end if
c
c  Shut down MPI.
c
      call MPI_Finalize ( error )

      stop
      end