setid Subroutine

   pure subroutine setid(mx, my, ns, nsd, lid, iwork)
   !! This routine sets the ID array in `iwork`, indicating which components are differential
   !! and which are algebraic.

      integer, intent(in) :: mx
      integer, intent(in) :: my
      integer, intent(in) :: ns
      integer, intent(in) :: nsd
      integer, intent(in) :: lid
      integer, intent(inout) :: iwork(*)

      integer :: i, i0, i00, jx, jy, nsdp1

      nsdp1 = nsd + 1
      do jy = 1, my
         i00 = mx*ns*(jy - 1) + lid
         do jx = 1, mx
            i0 = i00 + ns*(jx - 1)
            do i = 1, nsd
               iwork(i0 + i) = 1
            end do
            do i = nsdp1, ns
               iwork(i0 + i) = -1
            end do
         end do
      end do

   end subroutine setid