anchor.diff:  ! ---------------------------------------------------------------------------
   !> Compute derivatives of the depth field for the pressure solver
   
  -subroutine derivatives_of_the_depth_field(a, depth, g, dx, dy, nx, ny)
  +subroutine calc_A_matrix(a, depth, g, dx, dy, nx, ny)
     implicit none
   
     double precision, intent(out) :: a(5, nx, ny)
  
positive.code:   if (.not. RedGrav) then
      ! Initialise arrays for pressure solver
      ! a = derivatives of the depth field
        call derivatives_of_the_depth_field(a, depth, g_vec(1), dx, dy, nx, ny)
  
  #ifndef useExtSolver
      ! Calculate the spectral radius of the grid for use by the
  
negative.code:   end do
  
    return
  end subroutine calc_A_matrix
  
  ! ---------------------------------------------------------------------------
  
  