Synchronization Helps Robots to Detect Black Holes in Directed Graphs
OPODIS '09 Proceedings of the 13th International Conference on Principles of Distributed Systems
Mapping an unfriendly subway system
FUN'10 Proceedings of the 5th international conference on Fun with algorithms
Time optimal algorithms for black hole search in rings
COCOA'10 Proceedings of the 4th international conference on Combinatorial optimization and applications - Volume Part II
Synchronous black hole search in directed graphs
Theoretical Computer Science
Improving the optimal bounds for black hole search in rings
SIROCCO'11 Proceedings of the 18th international conference on Structural information and communication complexity
Black hole search with finite automata scattered in a synchronous torus
DISC'11 Proceedings of the 25th international conference on Distributed computing
FUN'12 Proceedings of the 6th international conference on Fun with Algorithms
Fault-Tolerant exploration of an unknown dangerous graph by scattered agents
SSS'12 Proceedings of the 14th international conference on Stabilization, Safety, and Security of Distributed Systems
Exploring an unknown dangerous graph using tokens
Theoretical Computer Science
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We study a group of mobile agents operating on an arbitrary unknown distributed system. One of the nodes of the distributed system is extremely harmful and destroys any incoming agent without notification. The task of exploring the distributed system and locating the harmful node, Black hole search, has been studied with various modifications.We are studying the effects of the knowledge of incoming link on the size of the optimal solution. When an agent enters a node, the information which port leads back can be given to it. We refer to this as to the knowledge of incoming link. In previous research, it was always assumed that the agent is given this information.In this paper we study arbitrary, unknown distributed systems without the knowledge of incoming link. Agents are asynchronous and they communicate via whiteboards. We present a lower bound on the size of the optimal solution, proving that at least $\frac{\Delta^2+\Delta}{2} + 1$ agents are necessary to locate the black hole, with respect to the degree of the black hole Δ. We provide an algorithm for black hole search without the knowledge of incoming link as well. We prove that this algorithm is correct, and that it uses $\frac{\Delta^2+\Delta}{2} + 1$ agents, thus providing optimal solution.