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Part II.3 Evaluation of algorithms. max. Scalar solution methods Population based methods Evaluation of algorithms. B. A. D. C. max. Performance assessment for Pareto optimization algorithms. Limit behavior of stochastic optimizers.
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Part II.3 Evaluation of algorithms max • Scalar solution methods • Population based methods • Evaluation of algorithms B A D C max
Limit behavior of stochastic optimizers Viewpoint 1: Randomized search heuristics Qualitative: Limit behavior for t → ∞ Probability{Optimum found} 1 Quantitative: Expected Running Time E(T) Algorithm A applied to Problem B 1/2 ∞ Computation Time (number of iterations)
Limit behavior of stochastic optimizers Viewpoint 2: Optimum approximation algorithms Qualitative: Limit behavior for t → ∞ Quality of solution Qmax Quantitative: Trade-off E(Solution Quality) vs. Time Algorithm A applied to Problem B ∞ Computation Time (number of iterations)
Limit Behavior of Multiobjective EA: Related Work • Requirements for archive: • Convergence • Diversity • Bounded Size [Rudolph 98,00] [Veldhuizen 99] [Rudolph 98,00] [Hanne 99] [Thiele et al. 02] convergence to whole Pareto front (diversity trivial) “store all” “store m” convergence to Pareto front subset (no diversity control) (impractical) (not sufficient)
The concept of archiving optimization archiving finitememory generate update, truncate finitearchive A
Bounded archive with diverse solutions 0 0 y2 y1
Theoretical Running Time Analysis for EA problem domain type of results • expected RT (bounds) • RT with high probability (bounds) [Mühlenbein 92] [Rudolph 97] [Droste, Jansen, Wegener 98,02][Garnier, Kallel, Schoenauer 99,00] [He, Yao 01,02] discrete search spaces Single-objective EAs • asymptotic convergence rates • exact convergence rates continuous search spaces [Beyer 95,96,…] [Rudolph 97] [Jagerskupper 03] [Laumanns, Thiele, Deb, Zitzler: GECCO2002] [Laumanns, Thiele, Zitzler, Welzl, Deb: PPSN-VII] Multiobjective EAs discrete search spaces
Which technique is suited for which problem class? Theoretically (by analysis): difficult Limit behavior (unlimited run-time resources) Running time analysis Empirically (by simulation): standard Problems: randomness, multiple objectives Issues:quality measures, statistical testing, benchmark problems, visualization, …
Quality measures A A B B Is A better than B? independent ofuser preferences Yes (strictly) No dependent onuser preferences How much? In what aspects? Ideal: quality measures allow to make both type of statements
Comparisons in practise From: M. Emmerich, Single- and Multiobjective Optimization, ElDorado 2005
Compatibility and completeness of unary operators and their combinations
Compatibility and completeness of unary operators and their combinations
Averaging Pareto Fronts Plotting attainment surfaces: http://dbk.ch.umist.ac.uk/knowles/plot_attainments/ Viviane Grunert da Fonseca, Carlos M. Fonseca, and Andreia O. Hall. Inferential Performance Assessment of Stochastic Optimisers and the Attainment Function. In Eckart Zitzler, Kalyanmoy Deb, Lothar Thiele, Carlos A. Coello Coello, and David Corne, editors, First International Conference on Evolutionary Multi-Criterion Optimization, pages 213-225. Springer-Verlag. Lecture Notes in Computer Science No. 1993, 2001