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The procedure consists in fixing a number of values for the perturbation such that these values are significant for the instance: on average probability and not rare. After that, on runtime it will be possible to check the benchmark plot in order to get an average idea on the instances passed.
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Finding the perturbation algorithm for ILS is not an easy task. The main aim is not to get stuck at the same local minimum and in order to ensure this property, the undo operation is forbidden. Despite this, a good permutation has to consider a lot of values, since there exist two kind of bad
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Another procedure is to optimize a sub-part of the problem while keeping the not-undo property active. If this procedure is possible, all solutions generated after the perturbations tend to be very good. Furthermore the
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that tells which one is the most suitable value for a given perturbation, the best criterion is to get it adaptive. For instance
Battiti and Protasi proposed a reactive search algorithm for
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algorithm and after each perturbation they apply a standard local descent algorithm. Another way of adapting the perturbation is to change deterministically its strength during the search.
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to transform a local minimizer into the starting point for the next run has to be appropriately strong, but not too strong to avoid reverting to memory-less random restarts.
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Penna, Puca H.V.; Satori Ochi, L.; Subramanian, A. (2013). "An
Iterated Local Search heuristic for the Heterogeneous Fleet Vehicle Routing Problem".
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Lourenço, H.R.; Zwijnenburg M. (1996). "Combining the Large-Step
Optimization with Tabu-Search: Application to the Job-Shop Scheduling Problem".
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with a low value than when starting from a random point. The only caveat is to avoid confinement in a given attraction basin, so that the
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The perturbation strength has to be sufficient to lead the trajectory to a different attraction basin leading to a different
414:"Using Iterated Local Search for solving the Flow-Shop Problem: parametrization, randomization and parallelization issues"
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Lourenço, H.R. (1995). "Job-Shop
Scheduling: computational study of local search and large-step optimization methods".
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which fits perfectly into the ILS framework. They perform a "directed" perturbation scheme which is implemented by a
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calls to the local search routine, each time starting from a different initial configuration. This is called
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274:. Kluwer Academic Publishers, International Series in Operations Research & Management Science.
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Lourenço, H.R.; Martin O.; Stützle T. (2010). "Iterated Local Search: Framework and
Applications".
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Iterated Local Search is based on building a sequence of locally optimal solutions by:
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Juan, A.A.; Lourenço, H.; Mateo, M.; Luo, R.; Castella, Q. (2013).
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applying local search after starting from the modified solution.
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291:"Reactive search, a history-sensitive heuristic for MAX-SAT"
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methods for solving discrete optimization problems.
418:International Transactions in Operational Research
289:Battiti, Roberto; Protasi, Marco (1997-01-01).
266:Lourenço, H.R.; Martin O.; Stützle T. (2003).
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139:Since there is no function
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272:Handbook of Metaheuristics
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184:as well as many others.
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109:Perturbation Algorithm
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433:Journal of Heuristics
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