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c.
dA:
Sub-ET 1
Sub-ET 2
A
A
a
O
A
O
O
b
N
O
a
c
c
b
a
a
b
dB:
Sub-ET 1
Sub-ET 2
O
O
c
a
b
b
Figure 3.27. Continued.
homogenizing tendencies of recombination). However, together with muta-
tion, inversion, and transposition, these operators work wonderfully and play
an important part in the creation of good solutions to virtually all problems.
Gene Recombination
In the third kind of GEP recombination, entire genes are exchanged between
two parent chromosomes, forming two new daughter chromosomes contain-
ing genes from both parents. Thus, the gene recombination operator ran-
domly chooses the two parent chromosomes and the gene to be exchanged.
Typically, a small gene recombination rate p gr of 0.3 is used as this operator
is seldom used as the only source of genetic variation.
The last two populations shown in Figure 3.28 are the outcome of an evolu-
tionary process in which the only source of genetic variation was gene recom-
bination at a much higher rate of 0.8. For this simple problem, again the ma-
jority function problem, it was possible to find a perfect solution only by shuf-
fling the genes already present in the initial population. Obviously, we wouldn't
have been that lucky with a more complex problem, unless huge populations
had been used. Note also that, with this operator, genes never trade places in
the chromosome, always occupying the same position. Indeed, genes can only
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