anchor.diff:      end subroutine advect_u
   
   
  -    subroutine advect3d(q,u,v,w,rho,dz,nx,nz,ny,debug,options)
  +    subroutine advect3d(q,u,v,w,rho,dz,nx,nz,ny,debug,options, err)
           implicit none
           real,dimension(1:nx,1:nz,1:ny), intent(inout) :: q
           real,dimension(1:nx,1:nz,1:ny), intent(in) :: w
  
positive.code:     integer :: order
      public:: mpdata, mpdata_init
      public:: advect_u, advect_w, advect_v ! for test_mpdata testing only!
  
  contains
      subroutine flux2(l,r,U,nx,nz,ny,f)
  
negative.code:         real,intent(in)::dt
          
          real::dx
          integer::nx,nz,ny,i, error
          
          dx=domain%dx
          nx=size(domain%dz,1)
          nz=size(domain%dz,2)
  