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Restricted Space Algorithms for Isomorphism on Bounded Treewidth Graphs

Abstract : The Graph Isomorphism problem restricted to graphs of bounded treewidth or bounded tree distance width are known to be solvable in polynomial time [Bod90],[YBFT99]. We give restricted space algorithms for these problems proving the following results: - Isomorphism for bounded tree distance width graphs is in L and thus complete for the class. We also show that for this kind of graphs a canon can be computed within logspace. - For bounded treewidth graphs, when both input graphs are given together with a tree decomposition, the problem of whether there is an isomorphism which respects the decompositions (i.e. considering only isomorphisms mapping bags in one decomposition blockwise onto bags in the other decomposition) is in L. - For bounded treewidth graphs, when one of the input graphs is given with a tree decomposition the isomorphism problem is in LogCFL. - As a corollary the isomorphism problem for bounded treewidth graphs is in LogCFL. This improves the known TC1 upper bound for the problem given by Grohe and Verbitsky [GroVer06].
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Submitted on : Wednesday, February 10, 2010 - 5:08:54 PM
Last modification on : Monday, August 19, 2019 - 4:20:06 PM
Long-term archiving on: : Friday, June 18, 2010 - 8:02:33 PM


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  • HAL Id : inria-00455593, version 1



Bireswar Das, Jacobo Toran, Fabian Wagner. Restricted Space Algorithms for Isomorphism on Bounded Treewidth Graphs. 27th International Symposium on Theoretical Aspects of Computer Science - STACS 2010, Inria Nancy Grand Est & Loria, Mar 2010, Nancy, France. pp.227-238. ⟨inria-00455593⟩



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