Searching for a black hole in synchronous tree networks

Jurek Czyzowicz, Dariusz Kowalski, Euripides Markou, Andrzej Pelc

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


A black hole is a highly harmful stationary process residing in a node of a network and destroying all mobile agents visiting the node, without leaving any trace. We consider the task of locating a black hole in a (partially) synchronous tree network, assuming an upper bound on the time of any edge traversal by an agent. The minimum number of agents capable of identifying a black hole is two. For a given tree and given starting node we are interested in the fastest-possible black hole search by two agents. For arbitrary trees we give a 5/3-approximation algorithm for this problem. We give optimal black hole search algorithms for two 'extreme' classes of trees: the class of lines and the class of trees in which any internal node (including the root which is the starting node) has at least two children.

Original languageEnglish (US)
Pages (from-to)595-619
Number of pages25
JournalCombinatorics Probability and Computing
Issue number4
StatePublished - Jul 2007
Externally publishedYes

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Statistics and Probability
  • Computational Theory and Mathematics
  • Applied Mathematics


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