C	/* 
C	 * The proc 0 and proc 1 send to proc 2 separately,
C	 * proc 2 call MPI_PROBE to know whether the messages come,
C	 * if so, it calls MPI_RECV to receive the messages
C	 * Compile: mpif77 mpi_probe01.f -o mpi_probe01
C	 * Run: mpirun -np 3 mpi_probe01
C	 */

	program main
	include 'mpif.h'

	integer rank, tag
	integer ierr, n, i
	real x
	integer status(MPI_STATUS_SIZE)

	tag = 0
	CALL MPI_INIT(ierr)
	CALL MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
	IF (rank.EQ.0) THEN 
		print *, 'Proc 0: Sleep for 5 sec before send...'
		CALL SLEEP(5)
		print *, 'Proc 0: Sending message...'
		CALL MPI_SEND(i, 1, MPI_INTEGER, 2, tag, MPI_COMM_WORLD, ierr) 
	ELSE IF(rank.EQ.1) THEN 
		print *, 'Proc 1: Sleep for 3 sec before send...'
		CALL SLEEP(3)
		print *, 'Proc 1: Sending message...'
		CALL MPI_SEND(x, 1, MPI_REAL, 2, tag, MPI_COMM_WORLD, ierr) 
	ELSE	! rank.EQ.2 
		DO n=1, 2 
			print *, 'Proc 2: Wait for message comes...'
			CALL MPI_PROBE(MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, status, ierr)
			print *, 'Proc 2: New message...'
			IF (status(MPI_SOURCE) .EQ. 0) THEN
				CALL MPI_RECV(i, 1, MPI_INTEGER, 0, tag, MPI_COMM_WORLD, status, ierr) 
			ELSE 
				CALL MPI_RECV(x, 1, MPI_REAL, 1, tag, MPI_COMM_WORLD, status, ierr) 
			END IF 
			print *, 'Proc 2: Received message from Proc ',status(MPI_SOURCE),' successfully!!'
		END DO 
	END IF 

	call MPI_FINALIZE(ierr)
	end