anchor.diff:  c     # to 'qcoarse' at face 'iside'  in direction 'idir' of 'qcoarse'
   c     # Assume this is mapped.
         subroutine mb_average_face_ghost(mx,my,mbc,meqn,qcoarse,
  -     &      qfine,auxcoarse, auxfine,
  +     &      qfine,areacoarse, areafine,
        &      idir,iface_coarse,p4est_refineFactor,refratio,igrid)
         implicit none
   
  
positive.code:       integer p4est_refineFactor
        double precision qfine(1-mbc:mx+mbc,1-mbc:my+mbc,meqn)
        double precision qcoarse(1-mbc:mx+mbc,1-mbc:my+mbc,meqn)
        double precision auxcoarse(1-mbc:mx+mbc,1-mbc:my+mbc,1)
        double precision auxfine(1-mbc:mx+mbc,1-mbc:my+mbc,1)
  
        double precision sum, kf, kc, qf
  
  
negative.code:                         ifine = (ibc-1)*refratio + ii
                          jfine = (jbc-1)*refratio + jj
                          qf = qfine(mx+1-ifine,jfine,mq)
                          kf = areafine(mx+1-ifine,jfine)
                          sum = sum + kf*qf
                       enddo
                    enddo
                    kc = r2*areacoarse(mx+ibc,1-jbc)
                    qcoarse(mx+ibc,1-jbc,mq) = sum/r2
                 enddo
              enddo
  