Evolutionary Computation - Computational Intelligence in Time Series Forecasting - page 192

creatures that adapt best to the changed environment will be selected by nature to
survive.
5.1.1 The Mechanisms of Evolution
The subject of evolutionary theory is actually the genetic evolution of individuals
within a population . The population stores multiple solutions of the given problem,
with each solution being a member of this population.
Associated with each member is its fitness , which is simply a measure of how
well this solution solves the problem. Throughout the search for the optimal
solution, a survival of the fittest procedure is used, which means that a solution
with a high fitness is chosen over one with a lower fitness. The main difference
between individual evolutionary algorithms is the way in which new solutions (or
offspring ) are generated from the existing members. There are two possible ways:
two solutions are mated to form two new solutions or each member of the
population generates an offspring by mutation .
Genetic operators are operators (or mechanisms) that produce a change in the
genetic code of genes. The most common of them is mutation in its various forms
causing various effects like:
x Deletion , i.e . a part of the code is deleted. Deletions in genes usually cause
genetic disaster.
x Duplication , i.e. a part of the code is actually duplicated. Again, this also
causes some major problems.
x Cross-over , i.e. the physical exchange of parts of a gene for parts of
another gene. This is more commonly known as the exchange of genetic
material and, much like mutation, promotes variation in an individual. In
fact, this is the principle way in which children often get a combination of
genes from both parents.
x Reproduction , i.e. the most important genetic operation described below.
In nature, there are two types of reproduction: asexual reproduction and sexual
reproduction . Asexual reproduction is actually the splitting of a single individual
into two new individuals, e.g. as with bacteria. In sexual reproduction, two
individuals of the same species, the male and the female , produce an offspring.
The key difference between these two types of reproduction is that sexual
reproduction includes the exchange of genetic material of both parents, whereas
asexual does not, because the daughter cells, produced by splitting into two new
cells, are genetically identical with the original cells of the mother. Hence, in
sexual reproduction the offspring is a combination of its parents, having some traits
from its father and some from its mother, and even some traits that are the
combination of traits from both mother and father.
5.1.2 Evolutionary Algorithms
The study of evolutionary behaviour of biological processes has produced a
qualitatively new background knowledge and a constructive impact on
development of new intelligent computational approaches to solving complex