ccccccccccccccccccccccccc     Program 12.5     cccccccccccccccccccccccccc
c
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c                                                                      c
c Please Note:                                                         c
c                                                                      c
c (1) This computer program is part of the book, "An Introduction to   c
c     Computational Physics," written by Tao Pang and published and    c
c     copyrighted by Cambridge University Press in 1997.               c
c                                                                      c
c (2) No warranties, express or implied, are made for this program.    c
c                                                                      c
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
c
      PROGRAM TALK_0_TO_1
      INCLUDE 'mpif.h'
      INTEGER IRANK,IPROC,ITAG,ISEND,IRECV,IERR,IM,ID,
     &        ISTAT(MPI_STATUS_SIZE),IFINISH
      CHARACTER*40 HELLO
C
      ITAG  = 730
      ID    = 40
      ISEND = 0
      IRECV = 1
      CALL MPI_INIT (IERR)
      CALL MPI_COMM_RANK (MPI_COMM_WORLD,IRANK,IERR)
      CALL MPI_COMM_SIZE (MPI_COMM_WORLD,IPROC,IERR)
      PRINT*, IRANK, IPROC
      CALL MPI_BARRIER (MPI_COMM_WORLD,IERR)
      IF (IRANK.EQ.ISEND) THEN
        HELLO = 'I am process 0, who are you ?'
        IM = 29
        CALL MPI_SEND (HELLO,IM,MPI_CHARACTER,IRECV,
     &                 ITAG,MPI_COMM_WORLD,IERR)
        PRINT*, 'I sent the message: ', HELLO
      ELSE IF (IRANK.EQ.IRECV) THEN
        CALL MPI_RECV (HELLO,ID,MPI_CHARACTER,ISEND,
     &                 ITAG,MPI_COMM_WORLD,ISTAT,IERR)
        PRINT*, 'I got your message which is: ', HELLO
      END IF
      CALL MPI_FINALIZE(IFINISH)
      STOP
      END