Parameterized Inapproximability of Target Set Selection and Generalizations
Résumé
In this paper, we consider the Target Set Selection problem: given a graph and a threshold value thr(v) for any vertex v of the graph, find a minimum size vertex-subset to "activate" s.t. all the vertices of the graph are activated at the end of the propagation process. A vertex v is activated during the propagation process if at least thr(v) of its neighbors are activated. This problem models several practical issues like faults in distributed networks or word-to-mouth recommendations in social networks. We show that for any functions f and ρ this problem cannot be approximated within a factor of ρ(k) in f(k)⋅nO(1) time, unless FPT = W[P], even for restricted thresholds (namely constant and majority thresholds). We also study the cardinality constraint maximization and minimization versions of the problem for which we prove similar hardness results.