Information Technology Reference
In-Depth Information
a.
012345678900123456789001234567890
AcOAbacbcbb-[3] = 8
AOabccbbabcAOabccbbabc
b.
Sub-ET
1
Sub-ET
2
Sub-ET
3
A
A
A
a
a
c
O
O
O
c
c
A
b
b
b
a
c
Figure 3.23.
A perfect solution to the majority function with a duplicated gene
(shown in bold). These, and all duplicated genes in gene expression programming,
get duplicated only by the combined effect of gene transposition and recombina-
tion.
a)
The three-genic chromosome with the duplicated genes highlighted.
b)
The
sub-ETs encoded in the chromosome.
3.3.5 Recombination
Gene expression programming uses three different kinds of recombination:
one-point recombination, two-point recombination, and gene recombination.
In all types of recombination, though, two chromosomes are randomly cho-
sen and paired to exchange some material between them, resulting in the
formation of two new individuals.
One-point Recombination
In one-point recombination the parent chromosomes are paired side by side
and split up at exactly the same point. The material downstream of the re-
combination point is afterwards exchanged between the two chromosomes.
In GEP, an event of recombination always involves two parent chromosomes
and always results in two new individuals. Usually the new daughter chro-
mosomes are as different from each other as they are from their mothers.
Figure 3.24 shows three populations - an initial population and two later
generations - obtained in a run in order to show the workings of one-point
recombination. Thus, in this experiment, the only source of genetic variation
was one-point recombination at a rate of
p
1r
= 0.8 so that the effects of this
operator could be clearly analyzed. By the results shown in Figure 3.24, you
