program closing_channels
  use iso_fortran_env, only: int32, real64
  implicit none

  integer(int32) :: j
  logical :: more, ok

  ! In this example we'll use a `jobs` array to communicate work to be done 
  ! from the main program to a worker image. When we have no more jobs for
  ! the worker we'll use synchronization to indicate completion.

  integer(int32), codimension[:] :: jobs(5)[*]
  logical, codimension[:] :: done[*]

  ! Here's the worker image. It repeatedly receives from `jobs` until 
  ! synchronization indicates that all jobs have been processed.
  ! We use this to notify on `done` when we've worked all our jobs.

  if (this_image() == 2) then
    do
      sync images(1)
      if (jobs(1)[1] == -1) then
        print *, "received all jobs"
        done[1] = .true.
        exit
      else
        print *, "received job", jobs(1)[1]
        jobs(1)[1] = 0  ! Mark job as processed
      end if
    end do
  end if

  ! This sends 3 jobs to the worker over the `jobs` array, 
  ! then signals completion.
  if (this_image() == 1) then
    do j = 1, 3
      jobs(1)[2] = j
      print *, "sent job", j
      sync images(2)
    end do
    jobs(1)[2] = -1  ! Signal end of jobs
    print *, "sent all jobs"
    sync images(2)

    ! We await the worker using synchronization.
    do while (.not. done[2])
      sync images(2)
    end do

    ! In Co-array Fortran, we don't have the concept of closed channels.
    ! Instead, we use explicit synchronization and flags to indicate
    ! completion of work.
    print *, "All jobs processed"
  end if

end program closing_channels