C
C	The root node sends out a message process 1. Process 1 send back to Process 0.
C
	program main
	include 'mpif.h'

	parameter (BUFSIZE = 64)
	integer my_rank, n_processes, tag
	integer ierr
	integer count, size
	integer status(MPI_STATUS_SIZE)
	double precision buf(BUFSIZE)

	size = BUFSIZE
	tag = 2001
	call MPI_INIT(ierr)
	call MPI_COMM_RANK(MPI_COMM_WORLD, my_rank, ierr)
	call MPI_COMM_SIZE(MPI_COMM_WORLD, n_processes, ierr)

	if (my_rank .eq. 0) then
C		/* send to the next node */
		print *, 'Hello world! I am ', my_rank, ' of ', n_processes,
	1	', sending to Proc ', my_rank+1

		call MPI_SEND(buf, size, MPI_DOUBLE_PRECISION, my_rank+1,
	1	tag, MPI_COMM_WORLD, ierr)

C		/* recieve from the last node */
		call MPI_RECV(buf, size, MPI_DOUBLE_PRECISION, n_processes-1,
	1	tag, MPI_COMM_WORLD, status, ierr)

		call MPI_GET_COUNT(status, MPI_DOUBLE_PRECISION, count, ierr)
		print *, 'Hello world! I am ', my_rank, ' of ', n_processes,
	1	', recv ', count,' entries from proc 0'
	else
C		/* recieve from the previous node */
		call MPI_RECV(buf, size, MPI_DOUBLE_PRECISION, my_rank-1, tag,
	1	MPI_COMM_WORLD, status, ierr)

		call MPI_GET_COUNT(status, MPI_DOUBLE_PRECISION, count, ierr)
		print *, 'Hello world! I am ', my_rank, ' of ', n_processes,
	1	', recv ', count,' entries from Proc 0'

C		/* send to the next node */
		print *, 'Hello world! I am ', my_rank, ' of ', n_processes, ' sending to Proc 0'
		call MPI_SEND(buf, size, MPI_DOUBLE_PRECISION, 0, tag, MPI_COMM_WORLD, ierr)
	endif

	call MPI_FINALIZE(ierr)
	end