anchor.diff:        subroutine mb_interpolate_block_corner_ghost(mx,my,mbc,meqn,
        &      refratio, qcoarse, qfine, icorner_coarse, iblock)
         implicit none
  -      integer mx, my, mbc, meqn, icorner_coarse, iblock, refratio,maux
  +      integer mx, my, mbc, meqn, icorner_coarse, iblock, refratio
         double precision qcoarse(1-mbc:mx+mbc,1-mbc:my+mbc,meqn)
         double precision qfine(1-mbc:mx+mbc,1-mbc:my+mbc,meqn)
   
  -      integer mq, ibc, jbc, ii, jj, r2, ifine, jfine
  +      integer mq, ibc, jbc, ii, jj, ifine, jfine
         integer ic, jc, mth
         double precision gradx, grady, shiftx, shifty
         double precision sl, sr, qc, value, compute_slopes
  
positive.code:                do ibc = 1,mbc
  c                 # ibc = 1 corresponds to first layer of ghost cells, and
  c                 # ibc = 2 corresponds to the second layer
                    sumfine = 0
                    do ii = 1,refratio
                       do jj = 1,refratio
                          ifine = (ibc-1)*refratio + ii
                          jfine = (j-1)*refratio + jj
                          if (iface_coarse .eq. 0) then
                             qf = qfine(ifine,jfine,mq)
                             areaf = areafine(ifine,jfine)
                          else
                             qf = qfine(mx+1-ifine,jfine,mq)
                             areaf = areafine(mx+1-ifine,jfine)
                          endif
                          sumfine = sumfine + qf*areaf
                       enddo
                    enddo
                    if (iface_coarse .eq. 0) then
                       areac = areacoarse(1-ibc,j+jc_add)
                       qcoarse(1-ibc,j+jc_add,mq) = sumfine/areac
                    else
                       areac = areacoarse(mx+ibc,j+jc_add)
                       qcoarse(mx+ibc,j+jc_add,mq) = sumfine/areac
                    endif
                 enddo
              enddo
  
negative.code:       implicit none
  
        integer mx,my,mbc,meqn,refratio,igrid,idir,iface_coarse
        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 areacoarse(-mbc:mx+mbc+1,-mbc:my+mbc+1)
        double precision areafine(-mbc:mx+mbc+1,-mbc:my+mbc+1)
  
        double precision sum, kf, kc, qf
  
        integer mq
        integer i, ic_add, ibc, ii, ifine
        integer j, jc_add, jbc, jj, jfine
  
  c     # 'iface' is relative to the coarse grid
  
  c     # Average fine grid onto coarse grid
        do mq = 1,meqn
  