Fitness Function of Chromosomes

The Fitness function is used to evaluate the pros and cons of each chromosome, or how the chromosome adapts to the environment. It is the basis for future genetic manipulation. Commonly used fitness functions are calculated in two ways  

One is rank-based fitness function the other is to set a fitness function through appropriate adjustments (called fitness scaling) of the actual target value. For the second method, in initial phase there are often chromosomes with a hypemormal fitness which constitute a larger proportion of the population if we reproduce them in proportion. Because of their outstanding competitiveness which may lead to their control of the selection process, they may further influence the global optimization 

This chapter deals with the fitness function based on sequence. pop size chromosomes of the population are arranged in descending order according to the values of the target function, which means the chromosomes are arranged from good to bad. Suppose the parameter a G (0,1) is given then the fitness function based on sequence is 

Because the chromosome with the best fitness does not necessarily appear in the last generation, the best chromosome marked Vb has to be reserved at the beginning calculation of iteration. If there is a better chromosome in the next generation then we use it to replace the former Vb- After completing the evolution, this chromosome can be taken as the solution of optimization problem. 

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