novel solution. Otherwise, if the average distance is
small, the point is in a dense region.
There exist some techniques for preserving
population diversity (e.g. crowding, sharing,
niching, etc.). They are widely used for finding
multiply optima (Mahfoud, 1995), but seem to be
unsuitable for a novelty search as their fitness
function is based on objectives.
We state the problem of the design of image
analysis technologies as an optimization problem
with two criteria: recognition accuracy and novelty
search. Thus, we have to use a multi-objective
technique instead of the standard GA. In this work,
we use an efficient approach called the self-
configuring coevolutionary multi-objective genetic
algorithm (SelfCOMOGA). The SelfCOMOGA was
introduced in (Ivanov and Sopov, 2013a) and its
effectiveness was investigated in (Ivanov and Sopov,
2013b).
One of the ways to develop self-configuring
search algorithms is the co-evolutionary approach
(Ficici, 2004).
Most of the works related to the co-evolutionary
multi-objective GA use the cooperative co-evolution
scheme, which implies the problem decomposition
of variables, objectives, population functionality,
etc. The fitness evaluation is based on the fitness
values of many individuals. Such a scheme shows
good performance, but requires the fine-tuning of
algorithm parameters, decomposition and
cooperation.
In the case of competitive co-evolution,
algorithms (populations) evolve independently over
some time. Then their performance is estimated.
Computational resources are redistributed to the
most effective algorithms. In addition, random
migrations of the best solutions are presented. The
competitive co-evolution scheme eliminates the
necessity to define an appropriate algorithm for the
problem as the choice of the best algorithm is
performed automatically during the run (Goh, 2007).
It is clear that applying the co-evolution scheme
provides the self-configuration for the given multi-
objective problem. Using different multi-objective
search approaches with fundamentally different
properties, the co-evolution algorithm is able to
improve the use of their individual advantages and
minimize the effects of the disadvantages.
The general SelfCOMOGA scheme is as follows:
Step 1. To define a set of multi-objective
algorithms included in the co-evolution.
Step 2. To perform algorithms run over some
time (called the adaptation period).
Step 3. To estimate the performance for each
algorithm over the adaptation period.
Step 4. To redistribute the computational
resources (population) and perform a new adaptation
period (go to the step 2).
We will discuss the SelfCOMOGA steps in
detail.
The first step defines the search strategies in the
form of the algorithms included. There are at least
three ways to form the algorithm set:
A pre-defined set of algorithms with special
performance features, which can be applied to
multi-objective problem solving:
All appropriate multi-objective algorithms;
A random selection of algorithms from the set
of all possible algorithms combinations.
The first way requires the involvement of a priori
knowledge of the problem and appropriate
algorithms. So it is not applicable to complex real-
world problems and contradicts the idea of the self-
configuring GA. The second approach is very
expensive because of the number of all algorithm
combinations (tens and hundreds). As shown in
(Ivanov and Sopov, 2013b), the third strategy
provides acceptable efficiency on average, and it is
not necessary to involve additional information
about the algorithms and their properties. This
option provides the best concept of the self-
configuring GA.
The adaptation period is a parameter of the co-
evolution algorithm. Numerical experiments show
that the parameter value is individual for each
problem and depends on the performance criteria of
the algorithm. Moreover, the value depends on the
limitation of the computational resource (total
number of fitness evaluations). It should be noted
that the algorithm is not sensitive to the parameter
on average with sufficient computational resources.
The key point of any co-evolutionary scheme is
the performance evaluation of the individual
algorithm. Since the performance is estimated using
the Pareto concept, a direct comparison of
algorithms is not possible, so well-known
approaches cannot be used. In various studies the
following criteria are proposed: the distance
(closeness) of the obtained solutions set to the true
Pareto set and the uniformity of the set of obtained
solutions. It is obvious that in real-world problems
the first criterion is not applicable because the true
Pareto set is a priori unknown. In this work we use
the following criteria combined into two groups.
The first group includes the static criteria (the
performance is measured over the current adaptation
period):
DesignEfficientTechnologiesforContextImageAnalysisinDialogHCIUsingSelf-ConfiguringNoveltySearchGenetic
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