Evolutionary Computation Glossary
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(biol) The dogma that nucleic acids act as
templates for the synthesis of proteins, but never the reverse. More generally, the dogma that
exert an influence over the form of a body, but the form of a body is never translated back into
genetic code: acquired characteristics are not inherited. cf
The dogma that the behaviour of the algorithm must be analysed using the
(life in general) The dogma that this all is useful in a way.
"You guys have a dogma. A certain irrational set of believes. Well, here's my irrational
set of beliefs. Something that works."
--- Rodney A. Brooks, [LEVY92]
(biol) One of the chains of
found in cells.
each encoded as a subsection of the DNA chain. Chromosomes are usually present in all cells in an
organism, even though only a minority of them will be active in any one cell.
A datastructure which holds a `string' of task parameters, or genes. This may be stored, for
example, as a binary bit-string, or an array of integers.
A system which takes a (set of)
inputs, and produces a (set of) outputs which indicate some classification of the inputs. An
example might take inputs from sensors in a chemical plant, and classify them in terms of: 'running
ok', 'needs more water', 'needs less water', 'emergency'. See Q1.4 for more information.
Some tasks involve
combining a set of entities in a specific way (e.g. the task of building a house). A general
combinatorial task involves deciding (a) the specifications of those entities (e.g. what size,
shape, material to make the bricks from), and (b) the way in which those entities are brought
together (e.g. the number of bricks, and their relative positions). If the resulting combination of
entities can in some way be given a
is the task of designing a set of entities, and deciding how they must be configured, so as to give
maximum fitness. cf
Notation originally proposed in
and the mu parents are discarded, leving only the lambda
to compete directly. Such a process is written as a (mu,lambda) search. The process of only
competing offspring then is a "comma strategy." cf.
is said to have
when 95% of the
all contain the same
for that gene. In some circumstances, a population can be said to have converged when all genes
have converged. (However, this is not true of populations containing multiple
Most people use "convergence" fairly loosely, to mean "the
has stopped finding new, better solutions". Of course, if you wait long enough, the GA will
*eventually* find a better solution (unless you have already found the global optimum). What people
really mean is "I'm not willing to wait for the GA to find a new, better solution, because I've
already waited longer than I wanted to and it hasn't improved in ages."
An interesting discussion on convergence by Michael Vose can be found in GA-Digest v8n22, available
The rate of error reduction.
The behavior of two or more
acting to increase the gains of all participating individuals.
which forms a new
by combining parts of each of two `parent' chromosomes. The simplest form is single-point
in which an arbitrary point in the chromosome is picked. All the information from
A is copied from the start up to the crossover point, then all the information from parent B is
copied from the crossover point to the end of the chromosome. The new chromosome thus gets the head
of one parent's chromosome combined with the tail of the other. Variations exist which use more
than one crossover point, or combine information from parents in other ways.
(biol) A complicated process which typically takes place as follows: chromosomes, while engaged
in the production of
exchange portions of genetic material. The result is that an almost infinite variety of gametes may
be produced. Subsequently, during sexual
male and female gametes (i.e. sperm and ova) fuse to produce a new
cell with a pair of chromosomes.
In [HOLLAND92] the sentence "When sperm and ova fuse,
matching chromosomes line up with one another and then cross their length, thus
swapping genetic material" is thus wrong, since these two activities occur in different parts of
the life cycle. [eds note: If sexual reproduction (the Real Thing) worked like in
then Holland would be right, but as we all know, it's not the case. We just encountered a
Freudian slip of a Grandmaster. BTW: even the German translation of this article has this
"bug", although it's well-hidden by the translator.]
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Hitch Hiker's Guide to Evolutionary Computation,
Issue 9.1, released 12 April 2001
Copyright © 1993-2001 by J. Heitkötter and
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