!> @brief Illustrates how to receive a message in a synchronous fashion.
!> @details This program is meant to be run with 2 processes: a sender and a
!> receiver.
PROGRAM main
USE mpi
IMPLICIT NONE
INTEGER :: ierror
INTEGER :: size
INTEGER, PARAMETER :: sender_rank = 0
INTEGER, PARAMETER :: receiver_rank = 1
INTEGER :: my_rank
INTEGER :: buffer
CALL MPI_Init(ierror)
! Get the number of processes and check only 2 processes are used
CALL MPI_Comm_size(MPI_COMM_WORLD, size, ierror)
IF (size .NE. 2) THEN
WRITE(*,'(A)') 'This application is meant to be run with 2 processes.'
CALL MPI_Abort(MPI_COMM_WORLD, -1, ierror)
END IF
! Get my rank and do the corresponding job
CALL MPI_Comm_rank(MPI_COMM_WORLD, my_rank, ierror)
SELECT CASE (my_rank)
CASE (sender_rank)
! The 'master' MPI process issues the MPI_Ssend.
buffer = 12345
WRITE(*,'(A,I0,A,I0,A)') 'MPI process ', my_rank, ' sends value ', buffer, '.'
CALL MPI_Ssend(buffer, 1, MPI_INTEGER, receiver_rank, 0, MPI_COMM_WORLD, ierror)
CASE (receiver_rank)
! The 'slave' MPI process receives the message.
CALL MPI_Recv(buffer, 1, MPI_INTEGER, sender_rank, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE, ierror)
WRITE(*,'(A,I0,A,I0,A)') 'MPI process ', my_rank, ' received value: ', buffer, '.'
END SELECT
CALL MPI_Finalize(ierror)
END PROGRAM main