Содержание
- 2. ES quick overview Developed: Germany in the 1970’s Early names: I. Rechenberg, H.-P. Schwefel Typically applied
- 3. ES technical summary tableau
- 4. Introductory example Task: minimimise f : Rn ? R Algorithm: “two-membered ES” using Vectors from Rn
- 5. Introductory example: pseudocde Set t = 0 Create initial point xt = 〈 x1t,…,xnt 〉 REPEAT
- 6. Introductory example: mutation mechanism z values drawn from normal distribution N(ξ,σ) mean ξ is set to
- 7. Illustration of normal distribution
- 8. Another historical example: the jet nozzle experiment Task: to optimize the shape of a jet nozzle
- 9. Another historical example: the jet nozzle experiment cont’d Jet nozzle: the movie
- 10. The famous jet nozzle experiment (movie)
- 11. Genetic operators: mutations (2) The one dimensional case
- 12. Representation Chromosomes consist of three parts: Object variables: x1,…,xn Strategy parameters: Mutation step sizes: σ1,…,σnσ Rotation
- 13. Mutation Main mechanism: changing value by adding random noise drawn from normal distribution x’i = xi
- 14. Mutate σ first Net mutation effect: 〈 x, σ 〉 ? 〈 x’, σ’ 〉 Order
- 15. Mutation case 1: Uncorrelated mutation with one σ Chromosomes: 〈 x1,…,xn, σ 〉 σ’ = σ
- 16. Mutants with equal likelihood Circle: mutants having the same chance to be created
- 17. Mutation case 2: Uncorrelated mutation with n σ’s Chromosomes: 〈 x1,…,xn, σ1,…, σn 〉 σ’i =
- 18. Mutants with equal likelihood Ellipse: mutants having the same chance to be created
- 19. Mutation case 3: Correlated mutations Chromosomes: 〈 x1,…,xn, σ1,…, σn ,α1,…, αk 〉 where k =
- 20. Correlated mutations cont’d The mutation mechanism is then: σ’i = σi • exp(τ’ • N(0,1) +
- 21. Mutants with equal likelihood Ellipse: mutants having the same chance to be created
- 22. Recombination Creates one child Acts per variable / position by either Averaging parental values, or Selecting
- 23. Names of recombinations
- 24. Parent selection Parents are selected by uniform random distribution whenever an operator needs one/some Thus: ES
- 25. Survivor selection Applied after creating λ children from the μ parents by mutation and recombination Deterministically
- 26. Survivor selection cont’d (μ+λ)-selection is an elitist strategy (μ,λ)-selection can “forget” Often (μ,λ)-selection is preferred for:
- 27. Self-adaptation illustrated Given a dynamically changing fitness landscape (optimum location shifted every 200 generations) Self-adaptive ES
- 28. Self-adaptation illustrated cont’d Changes in the fitness values (left) and the mutation step sizes (right)
- 29. Prerequisites for self-adaptation μ > 1 to carry different strategies λ > μ to generate offspring
- 30. Example application: the cherry brandy experiment Task to create a colour mix yielding a target colour
- 31. Example application: cherry brandy experiment cont’d Fitness: students effectively making the mix and comparing it with
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