Typically rank scaling assigns a fitness score to each chromosome based on its rank, r, such that better rankings (1,2,3,…) have disproportionately higher fitness scores. This can be achieved by randomly selecting from the top N or top x% of the ranked individuals, but more commonly some form of rank scaling is performed (second transform) and selection takes place from this modified dataset. This ranking ( fitness rank) is then used to guide selection of parents for reproduction, with higher ranking parents being selected preferentially. These real values are generally transformed, often twice, to create a standardized score that is then used in the selection of parents for reproduction.įitness is typically computed for all members of the population, at each generation of the procedure, and the fitness values for all members are then ranked (first transform) such that the fittest=Rank 1 and the least fit=Rank P, where P is the population size. The result of the fitness function is typically a real-valued number ( fitness value), with higher values assigned to better performing individuals. Hence for many geospatial problems the fitness function is simply based on the objective function of the problem, or some simplified or surrogate version of this that provides a suitable comparative measure and can be computed without excessive processor overhead. It measures how good a single individual is in terms of meeting the problem objective, e.g. Specification of a suitable fitness function is a key element in the design of a successful GA. Note that these last two representations require the use of very long strings as every element (gene) of the string (chromosome, genome) is a unique item from the dataset. ![]() identifying a set of discrete locations, such as cities or candidate facilities). Where again each gene corresponds to a separate data item and 103,12,33… represent index values of these data items (e.g.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |