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GAs and Premature Convergence

GAs and Premature Convergence. Premature convergence - GAs converge too early to suboptimal solution as the population gets homogeneous, only a little new can be evolved. Reasons for premature convergence: improper selection pressure insufficient population size deception

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GAs and Premature Convergence

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  1. GAs and Premature Convergence • Premature convergence - GAs converge too early to suboptimal solution • as the population gets homogeneous, only a little new can be evolved • Reasons for premature convergence: • improper selection pressure • insufficient population size • deception • improper representation and genetic operators

  2. Motivation and Realization • Motivation – to maintain a diversity of the evolved population and extend the explorative power of the algorithm • Realization • Convergence of the population is allowed up to specified extent • Convergence at individual positions of the representation is controlled • Convergence rate – specifies a maximal difference in the frequency of ones and zeroes in every column of the population • ranges from 0 to PopSize/2 • Principal condition – at any position of the representation neither ones nor zeroes can exceed the frequency constraint • Specific way of modifying the population genotype

  3. GALCO Algorithm GALCO– Genetic Algorithms with Limited Convergence 1. Generate initial population 2. Choose parents 3. Create offspring 4. if (offspring > parents) then replace parents with offspring else{ find(replacement) replace_with_mask(child1, replacement) find(replacement) replace_with_mask(child2, replacement) } 5. if (not finished) then go to step 2

  4. 50 Operator replace_with_mask Mask – vector of integer counters; stores a number of 1s for each bit of the representation

  5. Testovací úlohy - statické • Deceptive function • F101(x, y) • Hierarchická funkce • Royal Road Problem

  6. GALCO – vliv parametru C

  7. GALCO vs. SGA

  8. with replace_with_mask without replace_with_mask Multimodal Optimization Initial population SIGA

  9. Multimodal Optimization (cont.) Initial population GALCO SIGA

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