To use evolutionary search to can arrive at designs of self-checking circuits superior to those produced by conventional design. Self-checking circuits, are capable of signalling when a hardware fault has caused them to fail in performing their function. Self-checking circuits signalling faults as soon as they affect their behaviour are useful in mission critical applications such as medical equipment, transport and space missions.

The following table shows for which circuit types and sized we have evolved circuits superior to those of conventional design.

Fault ModelCircuit typeCircuit size
Single Combinational  
Multiple Combinational       

All evolved circuits details and diagrams can be found in the `Better than Human' Hall of Fame.


Combinational circuits' outputs only depend on circuit inputs.

A Sequential circuits' outputs depend on its inputs and on the state of its memory elements.

The Single Fault model assumes only one fault can happen at any time. Given the assumption that all input words are provided during normal operation between faults arriving, then these circuits will signal failure before the second fault arrives.

The Multiple Fault model assumes any number of faults can happen at any part of the circuit arriving one by one. There is no synthesis method for designing circuits which detect all combinations of multiple faults whithout the assumption of all input words been provided between fault arrivals. Thus the circuit Free-DC evolved by DHEP becomes the first to satisfy this property.