program ch2802
use mpi
implicit none
integer :: error_number
integer :: this_process_number
integer :: number_of_processes
integer :: i
integer, dimension (mpi_status_size) :: status

  call mpi_init(error_number)
  call mpi_comm_size(mpi_comm_world,number_of_processes,error_number)
  call mpi_comm_rank(mpi_comm_world,this_process_number,error_number)
  if (this_process_number==0) then
    print *, ' Hello from process ', this_process_number, ' of ', &
      number_of_processes, 'processes.'
    do i = 1, number_of_processes - 1
      call mpi_recv(this_process_number,1,mpi_integer,i,1,mpi_comm_world, &
        status,error_number)
      print *, ' Hello from process ', this_process_number, ' of ', &
        number_of_processes, 'processes.'
    end do
  else
    call mpi_send(this_process_number,1,mpi_integer,0,1,mpi_comm_world, &
      error_number)
  end if
  call mpi_finalize(error_number)
end program ch2802