Harmless Sets in Sparse Classes.

Felix Reidl
Irene Muzi
Pål Grønås Drange
Abstract: In the classic TARGET SET SELECTION problem, we are asked to minimise the number of nodes to activate so that, after the application of a certain propagation process, all nodes of the graph are active. Bazgan and Chopin [Discrete Optimization}, 14:170--182, 2014] introduced the opposite problem, named HARMLESS SET, in which they ask to maximise the number of nodes to activate such that not a single additional node is activated. In this paper we investigate how sparsity impacts the tractability of HARMLESS SET.

Specifically, we answer two open questions posed by the aforementioned authors, namely a) whether the problem is FPT on planar graphs and b) whether it is FPT parametrised by treewidth. The first question can be answered in the positive using existing meta-theorems on sparse classes, and we further show that HARMLESS SET not only admits a polynomial kernel, but that it can be solved in subexponential time. We then answer the second question in the negative by showing that the problem is W[1]-hard when parametrised by a parameter that upper bounds treewidth.

Cite this paper

@inproceedings{DBLP:conf/iwoca/DrangeMR22, author = {P{\aa}l Gr{\o}n{\aa}s Drange and Irene Muzi and Felix Reidl}, editor = {Cristina Bazgan and Henning Fernau}, title = {Harmless Sets in Sparse Classes}, booktitle = {Combinatorial Algorithms - 33rd International Workshop, {IWOCA} 2022, Trier, Germany, June 7-9, 2022, Proceedings}, series = {Lecture Notes in Computer Science}, volume = {13270}, pages = {299--312}, publisher = {Springer}, year = {2022}, url = {https://doi.org/10.1007/978-3-031-06678-8\_22}, doi = {10.1007/978-3-031-06678-8\_22}, timestamp = {Thu, 23 Jun 2022 19:55:38 +0200}, biburl = {https://dblp.org/rec/conf/iwoca/DrangeMR22.bib}, bibsource = {dblp computer science bibliography, https://dblp.org} }

Felix Reidl

Felix is a Senior Lecturer at Birkbeck. His speciality is the design of algorithms for sparse graphs.