box_lpl Subroutine

  subroutine box_lpl(mg, id, nc, i_out)
    type(mg_t), intent(inout) :: mg
    integer, intent(in)       :: id
    integer, intent(in)       :: nc
    integer, intent(in)       :: i_out
    !< Index of variable to store Laplacian in
    integer                   :: i, j
    real(dp)                  :: idr2(2)

    idr2 = 1 / mg%dr(:, mg%boxes(id)%lvl)**2

    associate (cc => mg%boxes(id)%cc, n => mg_iphi)
      do j = 1, nc
         do i = 1, nc
            cc(i, j, i_out) = idr2(1) * (cc(i-1, j, n) + cc(i+1, j,&
                n) - 2 * cc(i, j, n)) + idr2(2) * (cc(i, j-1, n) + cc(i, j+1,&
                n) - 2 * cc(i, j, n))
         end do
      end do
    end associate
  end subroutine box_lpl