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15828 Upper bounds and algorithms for parallel knock-out numbers
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Broersma, H.J. and Johnson, M. and Paulusma, D. (2009) Upper bounds and algorithms for parallel knock-out numbers. Theoretical Computer Science, 410 (14). pp. 1319-1327. ISSN 0304-3975 *** ISI Impact 0,943 ***

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Official URL: http://dx.doi.org/10.1016/j.tcs.2008.03.024

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Abstract

We study parallel knock-out schemes for graphs. These schemes proceed in rounds in each of which each surviving vertex simultaneously eliminates one of its surviving neighbours; a graph is reducible if such a scheme can eliminate every vertex in the graph. We resolve the square-root conjecture, first posed at MFCS 2004, by showing that for a reducible graph $G$, the minimum number of required rounds is $O(\sqrt{n})$; in fact, our result is stronger than the conjecture as we show that the minimum number of required rounds is $O(\sqrt{\alpha})$, where $\alpha$ is the independence number of $G$. This upper bound is tight. We also show that for reducible $K_{1,p}$-free graphs at most $p-1$ rounds are required. It is already known that the problem of whether a given graph is reducible is NP-complete. For claw-free graphs, however, we show that this problem can be solved in polynomial time. We also pinpoint a relationship with (locally bijective) graph homomorphisms.

Item Type:Article
Research Group:EWI-DMMP: Discrete Mathematics and Mathematical Programming
Research Program:CTIT-IE&ICT: Industrial Engineering and ICT
ID Code:15828
Status:Published
Deposited On:28 August 2009
Refereed:Yes
International:Yes
ISI Impact Factor:0,943
More Information:statisticsmetis

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