Mitchell, T. J. (2010) An exploration of evolutionary computation ...

strategy, with indicating a strategy with no recombination and and
equating to local and global recombination respectively.
More formally, intermediate recombination amongst
parents, is given by:
where represents the object parameter of the parent
, from which the recombinant object parameters , positioned at
the centre of mass or centroid of the contributing parents, may be derived. Discrete
recombination, on the other hand, is given by:
with chosen randomly anew for all .
Both recombination methods may be applied to the mutation step-sizes in addition to the
object parameters .
Eiben and Bäck (1997) empirically investigated the performance of a multi-membered ES
in application to a series of test functions, while varying the parameter . The paper
concludes that, in most cases, multisexual recombination of the object variables leads to an
increase in performance over asexual recombination (no recombination), with optimal
results often attained when (global recombination).
2.3.2.2 Genetic Repair
Beyer (2001) formally confirmed the positive effects of multisexual recombination with a
theoretical analysis of the ES applied to a simple unimodal sphere function. An
ES adopting global intermediate recombination was shown to provide an increase in
progress rates when compared with an equivalent ES without recombination. Beyer
attributed this increased rate to the corrective effects of the recombination operator, which
gave rise to the genetic repair hypothesis:
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