Introduction

Imagine a design space [1] where each point in that space represents the design of an electronic circuit. All possible electronic circuits are there, given the component types available to an electronics engineer, and the technological restrictions on how many components there can be and how they can interact. In this metaphor, we loosely visualise the circuits to be arranged in the design space so that `similar' circuits are close to each-other.

The design space is vast. There are oscillators and filters, finite-state machines, analogue computers, parallel distributed systems, von Neumann computers, and so on. These nestle amongst the majority of circuits for which a use will never be found. In this paper, we investigate the following hypotheses:

H1

Conventional design methods can only work within constrained regions of design space. Most of the whole design space is never considered.

H2

Evolutionary algorithms can explore some of the regions in design space that are beyond the scope of conventional methods. In principle, this raises the possibility that designs can be found that are in some sense better.

H3

Evolutionary algorithms in practice can produce designs that are beyond the scope of conventional methods and are, in some sense, better.

Note that the truth of each hypothesis relies in part on the truth of the preceding ones. In Section II we attempt to verify the first hypothesis by characterising what electronics designers normally do. Being essentially a work of anthropology, this is inevitably subjective and open to dispute. We judge that the basic conclusions are robust to variations in the exact details of how the designer's activities are conceptualised.

In the case studies of Sections III and IV, the second hypothesis is verified empirically, to a high degree of confidence. The hierarchical dependency of the hypotheses means that H1 is also strengthened.

In the final section, tools are presented for ongoing research to produce circuits through artificial evolution that are beyond the scope of conventional design, are in some sense better, and that are practically useful. This is the third hypothesis. From the experimental results, it is clear that there can be some special `niches' [1] for unusual circuits, but it remains to be seen how broadly they can be applied. We interpret our results as encouraging.