**Figure 6:** The scope of the iteration times for different problem dimensions (N) for (a)- the queens problem, (b)- the map colouring problem, (c)- the filtering problem. 1 iteration is approximately 1 second; the convergence is achieved with classical error energy functions, with *column, line and diagonal restrictions* for (a), *neighborhood restrictions* for (b), and *infinite norm Lyapunov* function for (c).

Tue Feb 9 20:20:27 JST 1999