get_partial_pack_mask Function

  function get_partial_pack_mask(this, upstream_grad) result(output)
    implicit none
    class(array_type), intent(inout) :: this
    type(array_type), intent(in) :: upstream_grad
    type(array_type) :: output
    type(array_type), pointer :: ptr

    if(allocated(this%indices))then
       ptr => unpack(upstream_grad, array_shape=this%adj_ja(2:,1), &
            dim = this%adj_ja(1,1), &
            indices = this%indices &
       )
    else
       ptr => unpack(upstream_grad, array_shape=this%adj_ja(2:,1), &
            dim = this%adj_ja(1,1))
    end if
    call output%assign_and_deallocate_source(ptr)
  end function get_partial_pack_mask