program hello_world
	use mpi
	implicit none
	integer ::  rank, nb_mpi_processes, ierror, hostname_len
	character (len=MPI_MAX_PROCESSOR_NAME) :: hostname
 
	!To enhance code readability, we let MPI call or MPI native variables in capital letters in Fortran
	call MPI_INIT(ierror) ! Init MPI (init MPI_COMM_WORLD communicator, set rank to each process, etc)

	call MPI_COMM_SIZE(MPI_COMM_WORLD, nb_mpi_processes, ierror) ! Ask the number of MPI processes running

	call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierror) ! Ask the rank of the current process

	call MPI_GET_PROCESSOR_NAME(hostname,hostname_len,ierror) ! Ask the name of the host the process is running on

	print*, 'Hello world ! I am process',rank,'on',nb_mpi_processes,'processes. I am running on',hostname ! Say hello

	call MPI_FINALIZE(ierror) ! Close MPI

end program hello_world