Abstract
Restarting is a technique used by many randomized local search and systematic search algorithms. If the algorithm has not been successful for some time, the algorithm is reset and reinitialized with a new random seed. However, for some algorithms and some problem instances, restarts are not beneficial. Luby et al. [12] showed that if restarts are useful, then there is a restart time \(t^*\) such that the so-called fixed-cutoff strategy is the best possible strategy in expectation.
In this work, we show that deciding whether restarts are useful is NP-complete. Furthermore, we show that there is no feasible approximation algorithm for the optimal restart time \(t^*\). Lastly, we show that calculating the expected runtime for a known probability distribution and a given restart time is \(\#\)P-complete.
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Lorenz, JH. (2019). On the Complexity of Restarting. In: van Bevern, R., Kucherov, G. (eds) Computer Science – Theory and Applications. CSR 2019. Lecture Notes in Computer Science(), vol 11532. Springer, Cham. https://doi.org/10.1007/978-3-030-19955-5_22
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DOI: https://doi.org/10.1007/978-3-030-19955-5_22
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