anchor.diff:    integer          :: i, j, k
     double precision :: loc(3), r
   
  +  ! Don't do anything here if the star no longer exists
  +
  +  phi = ZERO
  +
  +  if (mass_S == ZERO) return
  +
     do k = lo(3), hi(3)
        loc(3) = xlo(3) + (dble(k - lo(3)) + HALF) * dx(3)
        do j = lo(2), hi(2)
  
positive.code:                             lo,hi,domlo,domhi, &
                              dx,xlo,time,dt,bc,level,grid_no) bind(C)
  
    use bl_constants_module, only: HALF
    use probdata_module, only: mass_P, com_P
    use fundamental_constants_module, only: Gconst
  
  
negative.code: 
    integer          :: i, j, k
    double precision :: loc(3), r
  
    ! Don't do anything here if the star no longer exists
  
    phi = ZERO
  
    if (mass_P == ZERO) return
  
    do k = lo(3), hi(3)
       loc(3) = xlo(3) + (dble(k - lo(3)) + HALF) * dx(3)
  