Isomorphism Testing Parameterized by Genus and Beyond

Neuen, Daniel
(2021) Isomorphism Testing Parameterized by Genus and Beyond.
In: European Symposium on Algorithms.
Conference: ESA European Symposium on Algorithms

LIPIcs-ESA-2021-72.pdf - Published Version
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We present an isomorphism test for graphs of Euler genus g running in time 2^{O(g^4 log g)}n^{O(1)}. Our algorithm provides the first explicit upper bound on the dependence on g for an fpt isomorphism test parameterized by the Euler genus of the input graphs. The only previous fpt algorithm runs in time f(g)n for some function f (Kawarabayashi 2015). Actually, our algorithm even works when the input graphs only exclude K_{3,h} as a minor. For such graphs, no fpt isomorphism test was known before. The algorithm builds on an elegant combination of simple group-theoretic, combinatorial, and graph-theoretic approaches. In particular, we introduce (t,k)-WL-bounded graphs which provide a powerful tool to combine group-theoretic techniques with the standard Weisfeiler-Leman algorithm. This concept may be of independent interest.


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