Figure 4.

(a) Robustness, as measured in terms of degeneracy D_Z, increases with redundancy R_Z in a nonlinear fashion. Here, the first and second algorithms are indicated by means of triangles and circles, respectively. When the first is used, low levels of robustness are achieved, whereas evolution using fault tolerance leads to high robustness, provided that enough redundancy is at play. The inset shows the same results in log–log scale. In (b) we show the correlation between system size Z and fault tolerance. Here, we can clearly see that high levels of reliability are achieved by increasing the system's size. The inset shows the same plot in log–log scale, where we can appreciate a scaling behaviour.