| Circuit evolution is a kind of intelligent design method based on population-based algorithms and programmable hardware.It is a result of the development of evolutionary algorithms and programmable hardware.Recently,it has received more and more attentions,and has become a hot research field in the EHW field.Evolutionary techniques can find novel topologies of circuits;reduce the resources that are needed to build a circuit,increase transmission speeds of signals, etc.When the circuits are designed intrinsically,they can also have the characteristics of self-organizing,self-repairing and self-adaption.Therefore,the research on circuit evolution has great applicational value.Currently,the research on circuit evolution is still at the initial stage.Both intrinsic evolution and extrinsic evolution can only evolve small-scale circuits and it is hard to apply them in real world applications.The aim of this dissertation is to design effective algorithms and strategies for the evolutionary design of circuits and to do the corresponding experimental analyses by further exploring combinational circuit design methods,sequential circuit design methods and polymorphic circuit design methods.The main research works in this dissertation consist of the following aspects.(1) Based on the mending method,an efficient evolutionary design algorithm for combinational logic circuits is proposed.The evolutionary designing of circuits is now facing the problem of "stalling effect",which means that during the evolutionary process,the fitness value increases rapidly at the initial stage,however,when it reaches a certain percentage of maximum fitness value,the fitness value will increase very slowly.Based on the phenomenon of "stalling effect",the proposed algorithm switches to the mending stage after the initial stage.If the output is incorrect,the algorithm will mcnd the circuit to get the correct result.The empirical results demonstrate the proposed algorithm is effective.In order to mend the circuit(with minor errors) obtained from evolutionary process,a simple regular method for designing the additional mending circuit is proposed.The mending circuit is combined with the circuit that has some errors to form a 100%functionaly correct circuit.It can reduce evolutionary generations and time greatly. (2) For the evolutionary design of sequential logic circuits,a three step decomposition method named 3SD-ES is proposed.The algorithm integrates the decomposition method used in low-power techniques,the input decomposition method in the evolutionary design,the output decomposition method and ES.The experimental results show that this algorithm has better characteristic of expansion. The parameters of state decomposition,output decomposition and input decomposition affect each other.It is hard to set these parameters manually.In order to overcome this problem,an algorithm is proposed which can set the values automatically.(3) Based on the weighted sum method,an efficient evolutionary design algorithm for polymorphic circuits is proposed.Because the different functional circuits in the polymorphic circuit have different degree of difficulty,the algorithm based on the weighted sum method is proposed and the empirical results demonstrate that the algorithm has better performance than traditional EAs except for a few circuits.However,the weighted sum method needs a lot of experiments to evaluate the degree of difficulty beforehand in order to set appropriate weights.To overcome this problem,a dynamic weight adjustment method is proposed.Experiments demonstrate that this method is better than the algorithm based on weighted sum method.In this dissertation,the evolutionary algorithm ES is adopted for further exploring automatic and intelligent design of combinational logic circuits,sequential logic circuits and polymorphic circuits.The works in this dissertation not only can improve the research of evolutionary designing of circuits but also can promote the appilications of intelligent computation.
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