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A widely used class of algorithms for computing tree decompositions of graphs are heuristics that compute an elimination order, i.e., a permutation of the vertex set. In this paper, we propose to turbocharge these heuristics. For a target treewidth k, suppose the heuristic has already computed a partial elimination order of width at most k, but extending it by one more vertex exceeds the target width k. At this moment of regret, we solve a subproblem which is to recompute the last c positions of the partial elimination order such that it can be extended without exceeding width k. We show that this subproblem is fixed-parameter tractable when parameterized by k and c, but it is para-NP-hard and W[1]-hard when parameterized by only k or c, respectively. Our experimental evaluation of the FPT algorithm shows that we can trade a reasonable increase of the running time for quality of the solution.
@InProceedings{gaspers_et_al:LIPIcs.IPEC.2016.13,
author = {Gaspers, Serge and Gudmundsson, Joachim and Jones, Mitchell and Mestre, Juli\'{a}n and R\"{u}mmele, Stefan},
title = {{Turbocharging Treewidth Heuristics}},
booktitle = {11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
pages = {13:1--13:13},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-023-1},
ISSN = {1868-8969},
year = {2017},
volume = {63},
editor = {Guo, Jiong and Hermelin, Danny},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.13},
URN = {urn:nbn:de:0030-drops-69322},
doi = {10.4230/LIPIcs.IPEC.2016.13},
annote = {Keywords: tree decomposition, heuristic, fixed-parameter tractability, local search}
}