anchor.diff:  ! flip data back to the input orientation
   DO i=1,xdim
      DO j=1,ydim
  -      sout(i+iflip*(xdim+1-2*i),j+jflip*(ydim+1-2*j)) = s(i,j)
  +      sout(i+iflip*(xdim+1-2*i),j+jflip*(ydim+1-2*j)) = s(j,i)
      ENDDO
   ENDDO
   
  
positive.code: alpha=t*sigma*vth*fwc**beta/2./vg
  g=nt*2.*vg/fwc**beta
  
  DO i=1,xdim
     gamm = g * REAL(i)
     DO k=1,zdim
        DO j=1,ydim
           nc=0.
           
           IF(s(i,j).gt.0.01)THEN
  
negative.code: alpha=st*sigma*vth*sfwc**beta/2./svg
  g=nt*2.*svg/sfwc**beta
  
  DO j=1,xdim
     gamm = g * REAL(j)
     DO k=1,zdim
        IF(tr(k).lt.t)THEN
           DO i=1,ydim
              nc=0.
              
              IF(s(i,j).gt.0.01)THEN
  