anchor.diff:         call relax_2D_5(lev,p,b,cA,nsweeps,nx,ny,nh)
   
       else
  - 
  +
          call relax_line_3D_8(lev,p,b,cA,nsweeps,nx,ny,nz,nh)
   
       end if
  
positive.code: 
                     d(k)   = cA(1,k,j,i)
                     ud(k)  = cA(2,k+1,j,i)
   
                     do k = 2,nz-1 !interior levels
                        rhs(k) = b(k,j,i) &
                             - cA(3,k,j,i)*p(k+1,j-1,i) - cA(3,k-1,j+1,i)*p(k-1,j+1,i) &
  
negative.code:     do k=l-1,1,-1
         xc(k) = xc(k)-gam(k+1)*xc(k+1)
      enddo
      !    endif
    end subroutine tridiag
  
    !----------------------------------------
  