Latency-Bounded Target Set Selection in Social Networks (1303.6785v2)

Abstract: Motivated by applications in sociology, economy and medicine, we study variants of the Target Set Selection problem, first proposed by Kempe, Kleinberg and Tardos. In our scenario one is given a graph $G=(V,E)$, integer values $t(v)$ for each vertex $v$ (\emph{thresholds}), and the objective is to determine a small set of vertices (\emph{target set}) that activates a given number (or a given subset) of vertices of $G$ \emph{within} a prescribed number of rounds. The activation process in $G$ proceeds as follows: initially, at round 0, all vertices in the target set are activated; subsequently at each round $r\geq 1$ every vertex of $G$ becomes activated if at least $t(v)$ of its neighbors are already active by round $r-1$. It is known that the problem of finding a minimum cardinality Target Set that eventually activates the whole graph $G$ is hard to approximate to a factor better than $O(2^{\log^{1-\epsilon}|V|})$. In this paper we give \emph{exact} polynomial time algorithms to find minimum cardinality Target Sets in graphs of bounded clique-width, and \emph{exact} linear time algorithms for trees.