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(a)
(b)
Fig.2.
Space-time diagrams for an epoch 2 rule. (a)
ρ
0
=0
.
194, (b)
ρ
0
=0
.
879. The
rule only classifies low or high densities.
(a)
(b)
Fig.3.
Space-time diagrams for an epoch 3 rule. (a)
ρ
0
=0
.
489, (b)
ρ
0
=0
.
510.
Block-expanding and vertical strips make their appearance.
The following, and last, epoch 4 sees the refinement of the vertical strips
strategy withfitness above 0.9 and steadily increasing. The propagating patterns
become less noisy and the strategy is little affected by the intrinsic stochasticity
of the update rule. Figure 4 illustrates the best solution found by evolution at
the end of epoch 4. The “zebra-like” moving patterns, which represent the most
e
>
cient strategies for evolved asynchronous automata, are different from those
found in the synchronous case. In fact, the asynchronous updating modes have
the effect of destroying or delaying the propagation of the long-range transversal
signals that carry information in the synchronous case (see figure 1). Thus, the
CA expands blocks of zeros and ones, which collide and annihilate. Small-block
