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dc.contributor.authorCurticapean, Radu
dc.contributor.authorDell, Holger
dc.contributor.authorFomin, Fedor
dc.contributor.authorGoldberg, Leslie Ann
dc.contributor.authorLapinskas, John
dc.PublishedCurticapean R, Dell H, Fomin V, Goldberg LA, Lapinskas J. A Fixed-Parameter Perspective on #BIS. Algorithmica. 2019;81(10):3844-3864eng
dc.description.abstractThe problem of (approximately) counting the independent sets of a bipartite graph (#BIS) is the canonical approximate counting problem that is complete in the intermediate complexity class #RHΠ1. It is believed that #BIS does not have an efficient approximation algorithm but also that it is not NP-hard. We study the robustness of the intermediate complexity of #BIS by considering variants of the problem parameterised by the size of the independent set. We map the complexity landscape for three problems, with respect to exact computation and approximation and with respect to conventional and parameterised complexity. The three problems are counting independent sets of a given size, counting independent sets with a given number of vertices in one vertex class and counting maximum independent sets amongst those with a given number of vertices in one vertex class. Among other things, we show that all of these problems are NP-hard to approximate within any polynomial ratio. (This is surprising because the corresponding problems without the size parameter are complete in #RHΠ1, and hence are not believed to be NP-hard.) We also show that the first problem is #W[1]-hard to solve exactly but admits an FPTRAS, whereas the other two are W[1]-hard to approximate even within any polynomial ratio. Finally, we show that, when restricted to graphs of bounded degree, all three problems have efficient exact fixed-parameter algorithms.en_US
dc.publisherSpringer Natureen_US
dc.rightsAttribution CC BYeng
dc.subjectApproximate countingeng
dc.subjectParameterised complexityeng
dc.subjectIndependent setseng
dc.titleA Fixed-Parameter Perspective on #BISen_US
dc.typePeer reviewed
dc.typeJournal article
dc.rights.holderCopyright 2019 The Author(s)en_US

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