anchor.diff:  
           do i = 2, pasx
               do j = 2, pasy-1
  -                temp1 = (eta(i-1,j)+eta(i+1,j)-2*eta(i,j))/(dx*dx)        &
  -                      + (eta(i,j-1)+eta(i,j+1)-2*eta(i,j))/(dy*dy)
  -                temp2 = ((eta(i+1,j)-eta(i-1,j))/(2*dx))**2               &
  -                      + ((eta(i,j+1)-eta(i,j-1))/(2*dy))**2
  +                temp1 = (eta(i-1,j) + eta(i+1,j) - 2*eta(i,j))/(dx*dx)        &
  +                      + (eta(i,j-1) + eta(i,j+1) - 2*eta(i,j))/(dy*dy)
  +                temp2 = ((eta(i+1,j) - eta(i-1,j))/(2*dx))**2               &
  +                      + ((eta(i,j+1) - eta(i,j-1))/(2*dy))**2
                   b(i,j) = (Bu+Ro*eta(i,j))*temp1 + Ro/2*temp2
                   q(i,j) = temp1
               end do
  
positive.code: 
          ! Calcul des vitesses
  
          if(saveu.EQ.1) then
              if(n.EQ.save*fsave) then
                  do i = 2, pasx
                      do j = 2, pasy-1
  
  
negative.code:      
          ! Red Black
  
          fin = .false.
          compt = 0
  
          do while (fin == 0)
              compt = compt + 1
              fin = .true.
  
              ! Deux passages alternes
  
  