Fault-tolerant exploration of an unknown dangerous graph by scattered agents

Abstract

Black hole search (Bhs) is the problem of mapping or exploring a network where there are dangerous sites (black holes) that eliminate any incoming searcher without leaving a discernible trace. Dangerous graph exploration (Dge) extends the Bhs problem to include dangerous links (black links). In the literature, both problems have only been studied under the assumption that no faults occur in the network during the exploration. In this paper, we examine the impact that link failures can have on the exploration of dangerous graphs. We study the Dge problem under the following conditions: there are multiple black holes and black links, the network topology is unknown, the searchers are initially scattered in arbitrary locations, and the system is totally asynchronous. In this difficult setting, we assume that links can fail during the computation. We present an algorithm that solves the Dge in the presence of such dynamic link failures. Our solution to the problem works with an optimum number of searchers in a polynomial number of moves. This is the first result dealing with fault-tolerant computations in dangerous graphs. © 2012 Springer-Verlag.