anchor.diff:        cont = get_context()
   
         dxdy = dx*dy
  -      do m = 1,meqn
  +      do m = 1,mfields
            if (fclaw2d_map_is_used(cont)) then
   C            sum(m) = 0
   c            c_kahan = 0
  
positive.code: c    # Output and diagnostics
  c    # ----------------------------------------------------------------------------------
        subroutine fclaw2d_clawpatch46_fort_conservation_check
       &      (mx,my,mbc,meqn,dx,dy,area,q,sum,c_kahan)
        implicit none
  
        integer mx,my,mbc,meqn
        double precision dx, dy, dxdy
        double precision sum(meqn), c_kahan
        double precision q(1-mbc:mx+mbc,1-mbc:my+mbc,meqn)
        double precision c, t, y
  
        include 'metric_terms.i'
  
negative.code:          else
              do j = 1,my
                 do i = 1,mx
                    y = q(i,j,m)*dxdy - c_kahan
                    t = sum(m) + y
                    c_kahan = (t-sum(m)) - y
                    sum(m) = t
                    !!sum(m) = sum(m) + q(i,j,m)*dxdy
                 enddo
              enddo
           endif
  