anchor.diff:  !                 ut(ib, jb) = ut(ib, jb) + T0(ntrac) ! entering cell
   !                 print *, 'ut(ia, jb)=', ut(ia, jb), &
   !                             ' ut(ib, jb)=', ut(ib, jb)
  -            else if(y1==dble(ja) .and. y1.ne.y0 .and. y1>y0) then ! moving in positive y direction
  +            else if(idint(y1)>idint(y0)) then
  +!             else if(y1==dble(ja) .and. y1>y0) then ! moving in positive y direction
   !                 print *, 'moving in positive y direction'
   !                 print *, 'vt(ib, ja)=', vt(ib, ja), &
   !                             ' vt(ib, jb)=', vt(ib, jb), &
  
positive.code: !                 ut(ib, jb) = ut(ib, jb) + T0(ntrac) ! entering cell
  !                 print *, 'ut(ia, jb)=', ut(ia, jb), &
  !                             ' ut(ib, jb)=', ut(ib, jb)
              else if(x1==dble(ia-1) .and. x1.ne.x0 .and. x1<x0) then ! moving in negative x direction
  !                 print *, 'moving in negative x direction'
  !                 print *, 'ut(ia, jb)=', ut(ia, jb), &
  !                             ' ut(ib, jb)=', ut(ib, jb), &
  
negative.code: !                 vt(ib, jb) = vt(ib, jb) + T0(ntrac)
  !                 print *, 'vt(ib, ja)=', vt(ib, ja), &
  !                             ' vt(ib, jb)=', vt(ib, jb)
              else if(idint(y1)<idint(y0)) then
  !             else if(y1==dble(ja-1) .and. y1<y0) then ! moving in negative y direction
  !                 print *, 'moving in negative y direction'
  !                 print *, 'vt(ib, ja)=', vt(ib, ja), &
  !                             ' vt(ib, jb)=', vt(ib, jb), &
  