Subsections
Mutation is the random change of (usually small) parts of the genotype
of an individual. The first two mutation operators defined in this
section are the most important ones for continuous variables. The
Gaussian mutation operator is advantageous since it is very flexible
and supports both fine tuning of solutions and searching the domain.
Let
be a real variable. The random mutation
operator
changes
to
where
denotes the uniform distribution on the interval
. Thus the new value of
is independent from its previous
value.
is applied with a probability of a few percent. However
a much better and more versatile mutation operator is the Gaussian
mutation operator described in the following.
8.3.3.2 The Gaussian Mutation Operator
Let
be a real variable. Then the Gaussian mutation
operator
changes
to
where
may depend on the length
of the interval
and typically
.
is applied with
probability
to each variable, where
generally has a value
of a few percent. The value of
may also depend on time, i.e.,
the number of the current generation, and usually decreases with time.
The reason for a decreasing
is that stronger mutation during
the beginning of an optimization supports the sampling of the search
space and smaller displacements towards the end aid in fine tuning
extremum values.
Another advantageous setup is to use two mutation operators: one with
a high and one with a low value of
. This enables to achieve
a similar effect as a decreasing
.
Clemens Heitzinger
2003-05-08