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Preface
Bob Stern of CRC Press, to whom I am indebted, approached me in late 1999
asking if I was interested in developing a second edition of volume I of the
Practical Handbook of Genetic Algorithms. My immediate response was an
unequivocal “Yes!” This is the fourth book I have edited in the series and each
time I have learned more about GAs and people working in the field. I am proud
to be associated with each and every person with whom I have dealt with over the
years. Each is dedicated to his or her work, committed to the spread of knowledge
and has something of significant value to contribute.
This second edition of the first volume comes a number of years after the
publication of the first. The reasons for this new edition arose because of the
popularity of the first edition and the need to perform a number of functions for
the GA community. These “functions” fall into two main categories: the need to
keep practitioners abreast of recent discoveries/learning in the field and to very
specifically update some of the best chapters from the first volume.
The book leads off with chapter 0, which is the same chapter as the first edition
by Jim Everett on model building, model testing and model fitting. An excellent
“How and Why.” This chapter offers an excellent lead into the whole area of
models and offers some sensible discussion of the use of genetic algorithms,
which depends on a clear view of the nature of quantitative model building and
testing. It considers the formulation of such models and the various approaches
that might be taken to fit model parameters. Available optimization methods are
discussed, ranging from analytical methods, through various types of hillclimbing,
randomized search and genetic algorithms. A number of examples
illustrate that modeling problems do not fall neatly into this clear-cut hierarchy.
Consequently, a judicious selection of hybrid methods, selected according to the
model context, is preferred to any pure method alone in designing efficient and
effective methods for fitting parameters to quantitative models.
Chapter 1 by Roubos and Setnes deals with the automatic design of fuzzy rulebased
models and classifiers from data. It is recognized that both accuracy and
transparency are of major importance and we seek to keep the rule-based models
small and comprehensible. An iterative approach for developing such fuzzy rulebased
models is proposed. First, an initial model is derived from the data.
Subsequently, a real-coded GA is applied in an iterative fashion, together with a
rule-based simplification algorithm to optimize and simplify the model,
respectively. The proposed modeling approach is demonstrated for a system
identification and a classification problem. Results are compared to other
approaches in the literature. The proposed modeling approach is more compact
and interpretable.
Goldberg and Hammerham in Chapter 2, have extended their contribution to
Volume III of the series (Chapter 6, pp 119–238) by describing their current
research, which applies this technology to a different problem area, designing
automata that can recognize languages given a list of representative words in the
language and a list of other words not in the language. The experimentation
carried out indicates that in this problem domain also, smaller machine solutions
are obtained by the MTF operator than the benchmark. Due to the small variation
of machine sizes in the solution spaces of the languages tested (obtained
empirically by Monte Carlo methods), MTF is expected to find solutions in a
similar number of iterations as the other methods. While SFS obtained faster
convergence on more languages than any other method, MTF has the overall best
performance based on a more comprehensive set of evaluation criteria.
Taplin and Qiu, in Chapter 3, have contibuted material that very firmly grounds
GA in solving real-world problems by employing GAs to solve the very complex
problems associated with the staging of road construction projects. The task of
selecting and scheduling a sequence of road construction and improvement
projects is complicated by two characteristics of the road network. The first is that
the impacts and benefits of previous projects are modified by succeeding ones
because each changes some part of what is a highly interactive network. The
change in benefits results from the choices made by road users to take advantage
of whatever routes seem best to them as links are modified. The second problem
is that some projects generate benefits as they are constructed, whereas others
generate no benefits until they are completed.
There are three general ways of determining a schedule of road projects. The
default method has been used to evaluate each project as if its impacts and
benefits would be independent of all other projects and then to use the resulting
cost-benefit ratios to rank the projects. This is far from optimal because the
interactions are ignored. An improved method is to use rolling or sequential
assessment. In this case, the first year’s projects are selected, as before, by
independent evaluation. Then all remaining projects are reevaluated, taking
account of the impacts of the first-year projects, and so on through successive
years. The resulting schedule is still sub-optimal but better than the simple
ranking.
Another option is to construct a mathematical program. This can take account of
some of the interactions between projects. In a linear program, it is easy to specify
relationships such as a particular project not starting before another specific
project or a cost reduction if two projects are scheduled in succession. Fairly
simple traffic interactions can also be handled but network-wide traffic effects
have to be analysed by a traffic assignment model (itself a complex programming
task). Also, it is difficult to cope with deferred project benefits. Nevertheless,
mathematical programming has been used to some extent for road project
scheduling.
The novel option, introduced in this chapter, is to employ a GA which offers a
convenient way of handling a scheduling problem closely allied to the travelling
salesman problem while coping with a series of extraneous constraints and an
objective function which has at its core a substantial optimising algorithm to
allocate traffic.
The authors from City University of Hong Kong are Zhang, Chung, Lo, Hui, and
Wu. Their contribution, Chapter 4, deals with the optimization of electronic
circuits. It presents an implementation of a decoupled optimization technique for
the design of switching regulators. The optimization process entails selection of
the component values in the regulator to meet the static and dynamic
requirements. Although the proposed approach inherits characteristics of
evolutionary computations that involve randomness, recombination, and survival
of the fittest, it does not perform a whole-circuit optimization. Consequently,
intensive computations that are usually found in stochastic optimization
techniques can be avoided. In the proposed optimization scheme, a regulator is
decoupled into two components, namely, the power conversion stage (PCS) and
the feedback network (FN). The PCS is optimized with the required static
characteristics such as the input voltage and output load range, whils”t the FN is
optimized with the required static characteristics of the whole system and the
dynamic responses during the input and output disturbances. Systematic
procedures for optimizing circuit components are described. The proposed
technique is illustrated with the design of a buck regulator with overcurrent
protection. The predicted results are compared with the published results
available in the literature and are verified with experimental measurements.
Chapter 5 by Hallinan discusses the problems of feature selection and
classification in the diagnosis of cervical cancer. Cervical cancer is one of the
most common cancers, accounting for 6% of all malignancies in women. The
standard screening test for cervical cancer is the Papanicolaou (or “Pap”) smear,
which involves visual examination of cervical cells under a microscope for
evidence of abnormality.
Pap smear screening is labour-intensive and boring, but requires high precision,
and thus appears on the surface to be extremely suitable for automation. Research
has been done in this area since the late 1950s; it is one of the “classical”
problems in automated image analysis.
In the last four decades or so, with the advent of powerful, reasonably priced
computers and sophisticated algorithms, an alternative to the identification of
malignant cells on a slide has become possible.
The approach to detection generally used is to capture digital images of visually
normal cells from patients of known diagnosis (cancerous/precancerous condition
or normal). A variety of features such as nuclear area, optical density, shape and
texture features are then calculated from the images, and linear discriminant
analysis is used to classify individual cells as either “normal” or “abnormal.” An
individual is then given a diagnosis on the basis of the proportion of abnormal
cells detected on her Pap smear slide.
The problem with this approach is that while all visually normal cells from
“normal” (i.e., cancer-free) patients may be assumed to be normal, not all such
cells from “abnormal” patients will, in fact, be abnormal. The proportion of
affected cells from an abnormal patient is not known a priori, and probably varies
with the stage of the cancer, its rate of progression, and possibly other factors.
This means that the “abnormal” cells used for establishing the canonical
discriminant function are not, in fact, all abnormal, which reduces the accuracy of
the classifier. Further noise is introduced into the classification procedure by the
existence of two more-or-less arbitrary cutoff values – the value of the
discriminant score at which individual cells are classified as “normal” or
“abnormal,” and the proportion of “abnormal” cells used to classify a patient as
“normal” or “abnormal.”
GAs are employed to improve the ability of the system to discriminate and
therefore enhance classification.
Chapter 6, dealing with “Algorithms for Multidimensional Scaling,” offers
insights into looking at the potential for using GAs to map a set of objects in a
multidimensional space. GAs have a couple of advantages over the standard
multidimensional scaling procedures that appear in many commercial computer
packages. The most frequently cited advantage of Gas – the ability to avoid being
trapped in a local optimum – applies in the case of multidimensional scaling.
Using a GA or at least a hybrid GA, offers the opportunity to freely choose an
appropriate objective function. This avoids the restrictions of the commercial
packages, where the objective function is usually a standard function chosen for
its stability of convergence rather than for its applicability to the user’s particular
research problem. The chapter details genetic operators appropriate to this class of
problem, and uses them to build a GA for multidimensional scaling with fitness
functions that can be chosen by the user. The algorithm is tested on a realistic
problem, which shows that it converges to the global optimum in cases where a
systematic hill-descending method becomes entrapped at a local optimum. The
chapter also looks at how considerable computation effort can be saved with no
loss of accuracy by using a hybrid method. For hybrid methods, the GA is
brought in to “fine-tune” a solution, which has first been obtained using standard
multidimensional scaling methods.
Chapter 7 by Lam and Yin describes various applications of GAs to transportation
optimization problems. In the first section, GAs are employed as solution
algorithms for advanced transport models; while in the second section, GAs are
used as calibration tools for complex transport models. Both sections show that,
similar to other fields, GAs provide an alternative powerful tool to a wide variety
of problems in the transportation domain.
It is well-known that many decision-making problems in transportation planning
and management could be formulated as bilevel programming models (singleobjective
or multi-objectives), that are intrinsically non-convex and it is thus
difficult to find the global optimum. In the first example, a genetic-algorithmsbased
(GAB) approach is proposed to solve the single-objective models.
Compared with the previous heuristic algorithms, the GAB approach is much
simpler in principle and more efficient in applications. In the second example, the
GAB approach to accommodate multi-objective bilevel programming models is
extended. It is shown that this approach can capture a number of Pareto solutions
efficiently and simultaneously which can be attributed to the parallelism and
globality of GAs.
Varela, Vela, Puente, Gomez and Vidal in Chapter 8 describe an approach to
solve job shop scheduling problems by means of a GA which is adapted to the
problem in various ways. First, a number of adjustments of the evaluation
function are suggested; and then it is proposed that a strategy to generate a
number of chromosomes of the initial population allows the introduction of
heuristic knowledge from the problem domain. In order to do that, the variable
and value ordering heuristics proposed by Norman Sadeh are exploited. These are
a class of probability-based heuristics which are, in principle, set to guide a
backtracking search strategy. The chapter validates all of the refinements
introduced on well known benchmarks and reports experimental results showing
that the introduction of the proposed refinements has an accumulative and
positive effect on the performance of the GA.
Chapter 9, developed by Raich and Ghaboussi, discusses an evolutionary-based
method called the implicit redundant representation genetic algorithm (IRR GA)
is applied to evolve synthesis design solutions for an unstructured, multi-objective
frame problem domain. The synthesis of frame structures presents a design
problem that is difficult, if not impossible, for current design and optimization
methods to formulate, let alone search. Searching for synthesis design solutions
requires the optimization of structures with diverse structural topology and
geometry. The topology and geometry define the number and the location of
beams and columns in the frame structure. As the topology and geometry change
during the search process, the number of design variables also change. To support
the search for synthesis design solutions, an unstructured problem formulation
that removes constraints that specify the number of design variables is used.
Current optimization methods, including the simple genetic algorithm (SGA), are
not able to model unstructured problem domains since these methods are not
flexible enough to change the number of design variables optimized. The
unstructured domain can be modeled successfully using the location-independent
and redundant IRR GA representation.
The IRR GA uses redundancy to encode a variable number of locationindependent
design variables in the representation of the problem domain. During
evolution, the number and locations of the encoded variables dynamically change
within each individual and across the population. The IRR GA provides several
benefits: redundant segments protect existing encoded design variables from the
disruption of crossover and mutation; new design variables may be designated
within previously redundant segments; and the dimensions of the search space
dynamically change as the number of design variables represented changes. The
IRR GA synthesis design method is capable of generating novel frame designs
that compare favorably with solutions obtained using a trial-and-error design
process.
Craenen, Eiben and Marchiori in Chapter 10 develop a contribution that describes
evolutionary algorithms (EAs) for constraint handling. Constraint handling is not
straightforward in an EA because the search operators mutation and
recombination are “blind” to constraints. Hence, there is no guarantee that if the
parents satisfy some constraints the offspring will satisfy them as well. This
suggests that the presence of constraints in a problem makes EAs intrinsically
unsuited to solve this problem. This should especially hold when the problem
does not contain an objective function to be optimized, but only constraints – the
category of constraint satisfaction problems. A survey of related literature,
however, indicates that there are quite a few successful attempts to evolutionary
constraint satisfaction. Based on this survey, the authors identify a number of
common features in these approaches and arrive at the conclusion that EAs can be
effective constraint solvers when knowledge about the constraints is incorporated
either into the genetic operators, in the fitness function, or in repair mechanisms.
The chapter concludes by considering a number of key questions on research
methodology.
Chapter 11 provides a very valuable approach to fine-tuning fuzzy rules. The
chapter presents the design of a fuzzy logic controller (FLC) for a boost-type
power factor corrector. A systematic offline design approach using the genetic
algorithm to optimize the input and output fuzzy subsets in the FLC is proposed.
Apart from avoiding complexities associated with nonlinear mathematical
modeling of switching converters, circuit designers do not have to perform timeconsuming
procedures of fine-tuning the fuzzy rules, which require sophisticated
experience and intuitive reasoning as in many classical fuzzy-logic-controlled
applications. Optimized by a multi-objective fitness function, the proposed
control scheme integrates the FLC into the feedback path and a linear
programming rule on controlling the duty time of the switch for shaping the input
current waveform, making it unnecessary to sense the rectified input voltage. A
200-W experimental prototype has been built. The steady-state and transient
responses of the converter under a large-signal change in the supply voltage and
in the output load are investigated.
In Chapter 12, Grundler, from the University of Zagreb describes a new method
of complex process control with the coordinating control unit based upon a
genetic algorithm. The algorithm for the control of complex processes controlled
by PID and fuzzy regulators at the first level and coordinating unit at the second
level has been theoretically laid out. A genetic algorithm and its application to the
proposed control method have been described in detail. The idea has been verified
experimentally and by simulation in a two-stage laboratory plant. Minimal energy
consumption criteria limited by given process response constraints have been
applied, and improvements in relation to other known optimizing methods have
been made. Independent and non-coordinating PID and fuzzy regulator parameter
tuning have been performed using a genetic algorithm and the results achieved are
the same or better than those obtained from traditional optimizing methods while
at the same time the method proposed can be easily automated. Multilevel
coordinated control using a genetic algorithm applied to a PID and a fuzzy
regulator has been researched. The results of various traditional optimizing
methods have been compared with an independent non-coordinating control and
multilevel coordinating control using a genetic algorithm.
Chapter 13 discusses GA approaches to cancer treatment. The aim of radiation
therapy is to cure the patient of malignant disease by irradiating tumours and
infected tissue, whilst minimising the risk of complications by avoiding
irradiation of normal tissue. To achieve this, a treatment plan, specifying a
number of variables, including beam directions, energies and other factors, must
be devised. At present, plans are developed by radiotherapy physicists, employing
a time-consuming iterative approach. However, with advances in treatment
technology which will make higher demands on planning soon to be available in
clinical centres, computer optimisation of treatment plan parameters is being
actively researched. These optimisation systems can provide treatment solutions
that better approach the aims of therapy. However, direct optimisation of
treatment goals by computer remains a time-consuming and computationally
expensive process. With the increases in the demand for patient throughput, a
more efficient means of planning treatments would be beneficial. Previous work
by Knowles (1997) described a system which employs artificial neural networks
to devise treatment plans for abdominal cancers. Plan parameters are produced
instantly upon input of seven simple values, easily measured from the CT-scan of
the patient. The neural network used in Knowles (1997) was trained with fairly
standard backpropagation (Rumelhart et al., 1986) coupled with an adaptive
momentum scheme. This chapter focuses on later work in which the neural
network is trained using evolutionary algorithms. Results show that the neural
network employing evolutionary training exhibits significantly better
generalisation performance than the original system developed. Testing of the
evolutionary neural network on clinical planning tasks at Royal Berkshire
Hospital in Reading, UK, has been carried out. It was found that the system can
readily produce clinically useful treatment plans, considerably quicker than the
human-based iterative method. Finally, a new neural network system for breast
cancer treatment planning was developed. As plans for breast cancer treatments
differ greatly from plans for abdominal cancer treatments, a new network
architecture was required. The system developed has again been tested on clinical
planning tasks at Royal Berkshire Hospital and results show that, in some cases,
plans which improve on those produced by the hospital are generated.
For those of you who are well-entrenched in the field, there are authors that you
will recognise as being some of the best; and for those of you who are new to
Gas, the same will apply – these are names you will certainly come to know and
respect. The contributors to this edition come from a cross-section of academia
and industry – theoreticians and practitioners. All make a significant contribution
to our understanding of and ability to use GAs.
One of the main objectives of the series has been to develop a work that will allow
practitioners to take the material offered and use it productively in their own work.
This edition maintains that objective. To that end, some contributors have also
included computer code so that their work can be duplicated and used productively
in your own endeavours. I will willingly e-mail the code to you if you send a
request to
lchambers@transport.wa.gov.au or it may be found on the CRC Press
web site at
www.crcpress.com.
The science and art of GA programming and application has come a long way in
the last 5 years since the publication of the first edition. However, I consider GAs
as still being a “new science” that has a long way to go before the bounds of the
effects are well-defined and their ability to contribute in a meaningful manner to
many fields of human endeavour are exhausted. We are, metaphorically, still
“scratching the surface” of our understanding and applications of GAs. This book
is designed to help scratch that surface just a little bit deeper and a little bit more.
As in the previous volumes, authors have come from countries around the world.
In a world, which we are told is continually shrinking, it is pleasing to obtain first
hand evidence of this shrinkage. As in the earlier volumes all communications
were by e-mail which has dramatically sped up the whole process. But even so, a
work of this nature invariably takes time.
The development of a chapter contribution to any field of serious endeavour is a
task that must, of need, be taken on only after serious consideration and
contemplation. I am happy to say that I believe all the authors contributing to this
volume have gone through those processes and I believe that because of the
manifest quality of the work presented.
Lance Chambers
Perth, Western Australia
lchambers@transport.wa.gov.au
Note: I have not Americanised (sic) the spelling of English spelling contributors.
So, as you read, you will find a number of words with s’s where you may expect
z’s, and you may find a large number of u’s where you might least expect them as
in the word, “colour” and “behaviour.” Please do not be perturbed. I believe the
authors have the right to see their work in a form each recognises. I also have not
altered the referencing forms used (we all understand the various forms and this
should not detract from the book, but hopefully add some individuality) by the
authors.
Ultimately, however, I am responsible for all alterations, errors and omissions.
Crc Press - The Practical Handbook Of Genetic Algorithms Application IS GOOD BOOK ,THANK YOU