Abstract
Local search is the most basic strategy in optimization settings when no specific problem knowledge is employed. While this strategy finds good solutions for certain optimization problems, it generally suffers from getting stuck in local optima. This stagnation can be avoided if local search is modified. Depending on the optimization landscape, different modifications vary in their success.
We discuss several features of optimization landscapes and give analyses as examples for how they affect the performance of modifications of local search. We consider modifying random local search by restarting it and by considering larger search radii. The landscape features we analyze include the number of local optima, the distance between different optima, as well as the local landscape around a local optimum. For each feature, we show which modifications of local search handle them well and which do not.
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Notes
- 1.
The optimum of all test functions in this paper is given by the all-1 string, which leads to the observation that the optimum can be found in constant time by just conjecturing this string. Still theoretical research analyzes such functions, because (a) we can nonetheless observe the behavior of different algorithms on these functions, giving insights into the algorithms; and (b) these functions are representatives of much wider classes of functions with either isomorphic or at least similar properties, but for a theoretical analysis we restrict ourselves to the clean case where the rule “more 1 s means closer to the optimum” holds.
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Acknowledgments
This work was supported by a grant by the Independent Research Fund Denmark (DFF-FNU 8021-00260B), and by the Paris Île-de-France Region via the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 945298-ParisRegionFP.
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Friedrich, T., Kötzing, T., Krejca, M.S., Rajabi, A. (2022). Escaping Local Optima with Local Search: A Theory-Driven Discussion. In: Rudolph, G., Kononova, A.V., Aguirre, H., Kerschke, P., Ochoa, G., Tušar, T. (eds) Parallel Problem Solving from Nature – PPSN XVII. PPSN 2022. Lecture Notes in Computer Science, vol 13399. Springer, Cham. https://doi.org/10.1007/978-3-031-14721-0_31
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