The threshold also with real encoding coding scheme is as follows: θ1θ2⋯θm. (3) Here, the threshold of output layer neuron is also encoded by real number encoding method; θj represents the threshold of jth output neuron. supplier Seliciclib So, in conclusion, the complete coding strand of one chromosome is the combination of the structure, connection weight, and threshold, and it is as follows: c1c2⋯csw11w21⋯ws1w12w22 ⋯ws2⋯w1mw2m⋯wsmθ1θ2⋯θm.
(4) 3.1.2. Constructing Genetic Operator (1) Selection Operator. When it comes to the selection operator, in this paper, choose the proportional selection operator and use the roulette wheel selection, which is the most commonly used method in genetic algorithm. The individuals with
higher fitness will more likely be selected, while the individuals with lower fitness also have the chance to be selected, so that it keeps the diversity of the population under the condition of “survival of the fittest”. (2) Crossover Operator. We use single-point crossover operator as the crossover operator; each time we choose two individuals of parent generation to crossover so as to generate two new individuals, which are added into the new generation. We will repeat this procedure until the new generation population reaches the maximum size. We use single-point crossover although the complete procedure uses hybrid encoding; however, the crossover operation for binary encoding and real encoding is the same. The strategy of elitism selection is used here, that is, to retain several individuals with highest fitness to the next generation directly; this strategy prevents the loss of the optimal individual during the evolution. (3) Mutation Operator. Mutation operator uses reversal operator, as it uses hybrid encoding; different operations are applied
to different code system. Binary encoding uses bit-flipping mutation; that is to say, some bit of the chromosome may turn from 1 to 0 or 0 to 1. For real encoding, we use Gaussian mutation; that means some gene of the chromosome will add a random Gaussian number. 3.1.3. Calculate Fitness Fitness function evaluation is the basis of genetic selection, so it will directly affect the performance of genetic algorithm. Therefore, the selection of fitness function is very crucial; it directly affects the speed Entinostat of genetic algorithm convergence and whether we can find the optimal solution. The original data sets are divided into training data sets and testing data sets, using the network training error and the number of hidden neurons to determine the RBF neural networks’ corresponding fitness of the chromosomes. Suppose the training error is E, the number of hidden layer neurons is s, and upper limit of the number of hidden layer neurons is smax . So the fitness F is defined by F=C−E×ssmax.