Aalto University Schools of Technology - electronic academic dissertations - http://otalib.aalto.fi/fi/kokoelmat_tiedonhaku/e-julkaisut/vaitoskirjat/ | |
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Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S3 at Helsinki University of Technology (Espoo, Finland) on the 8th of December, 2006, at 12 noon.
Overview in PDF format (ISBN 951-22-8524-X) [4315 KB]
Dissertation is also available in print (ISBN 951-22-8523-1)
This dissertation deals with improving the reliability of evolutionary computation algorithms and accelerating problem-solving in optimization problems. Evolutionary algorithms have proven their value in difficult optimization problems that are not usually solvable in decent time using conventional optimization methods. However, evolutionary computation methods still suffer from problems related especially to premature convergence and the lengthy run times of the algorithms. In addition, the field of evolutionary computation does not commonly use the widely accepted practices for the comprehensive statistical comparison of two different evolutionary algorithms.
This dissertation aims at improving the process of using evolutionary computation in complex optimization problems from three perspectives. First, new algorithms are proposed for demanding optimization tasks. These algorithms rely on two perspectives, using a new multipopulation approach to enable appropriate conditions for candidate solutions to evolve and fusing evolutionary algorithms with other soft computing technologies, such as fuzzy logic, in a new way. Second, this dissertation discusses a method for reducing the computational time taken to evaluate a computationally demanding objective function value using neural network-based approximations. Third, a statistical method for comparing the results produced by two different evolutionary algorithms is illustrated. This method, relying on bootstrap resampling-based multiple hypothesis testing, is known outside the field of evolutionary computation, but has not been used within the evolutionary computing community. This dissertation illustrates the use of the statistical scheme and studies the parameters affecting the interpretation of its results.
The improvements to evolutionary algorithms this dissertation proposes have been proven to be beneficial by extensive testing. The proposed algorithms and the means to reduce the time required by the objective function evaluation have shown an increase in performance when compared to the reference algorithms. This dissertation also aims at awakening discussion related to the proper use of statistics in the field of evolutionary computation.
This thesis consists of an overview and of the following 8 publications:
Keywords: evolutionary computation, hybrid algorithm, optimization, statistical comparison
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© 2006 Helsinki University of Technology