Evolving more efficient digital circuits by allowing circuit layout evolution and multi-objective fitness

Abstract

We use evolutionary search to design combinational logic circuits. The technique is based on evolving the functionality and connectivity of a rectangular array of logic cells whose dimension is defined by the circuit layout. The main idea of this approach is to improve quality of the circuits evolved by the genetic algorithm (GA) by reducing the number of active gates used. We accomplish this by combining two ideas: 1) using multiobjective fitness function; 2) evolving circuit layout. It will be shown that using these two approaches allows us to increase the quality of evolved circuits. The circuits are evolved in two phases. Initially the genome fitness in given by the percentage of output bits that are correct. Once 100% functional circuits have been evolved, the number of gates actually used in the circuit is taken into account in the fitness function. This allows us to evolve circuits with 100% functionality and minimise the number of active gates in circuit structure. The population is initialised with heterogeneous circuit layouts and the circuit layout is allowed to vary during the evolutionary process. Evolving the circuit layout together with the function is one of the distinctive features of proposed approach. The experimental results show that allowing the circuit layout to be flexible is useful when we want to evolve circuits with the smallest number of gates used. We find that it is better to use a fixed circuit layout when the objective is to achieve the highest number of 100% functional circuits. The two-fitness strategy is most effective when we allow a large number of generations.

Extrinsic Evolution of Finite State Machine

“…The circuit evolution is performed using a rudimentary ) 1 ( + λ evolutionary strategy with uniform mutation [16]. The parameter circuit mutation is used to change the type of genes in chromosome excluding the number of columns and rows.…”

“…Recently a new area to design both combinational and sequential logic circuits known as evolvable hardware has been introduced [3]. EHW technique is based on evolving the functionality and connectivity of the rectangular array of logic cells in addition to the layout of this array [4]. There are different definitions of EHW depending on its purpose.…”

Evolutionary synthesis of low-sensitivity equalizers using adjacency matrix representation

“…In a large number of works found in the literature [5][6][7][8][9][10][11], a Genetic Algorithm (GA) is used just as an optimization method to find the multipliers values for a given fixed filter topology. On the other hand, among the works [12][13][14][15][16][17] addressing the evolutionary synthesis methods only a few deal with the lowsensitivity problem [16][17]. Several equivalent filter structures are able to realize the same transfer function.…”

On Evolution of Relatively Large Combinational Logic Circuits

“…At the second level the array of cells is created and the circuit's outputs are determined. The third level represents the structures of each cell in the circuit [19].…”

“…The evolutionary algorithm used is the (1+λ) rudimentary evolutionary strategy with cell and circuit geometry mutation, where λ represents the population size [19], [20]. Once the fitness function of each individual is calculated, the fittest individual is selected and duplicated for the population of the next generation and it is brought up to date by using both cell and circuit geometry mutation operators.…”