Rendezvous of Distance-Aware Mobile Agents in Unknown Graphs

  • Shantanu Das
  • Dariusz Dereniowski
  • Adrian Kosowski
  • Przemysław Uznański
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8576)


We study the problem of rendezvous of two mobile agents starting at distinct locations in an unknown graph. The agents have distinct labels and walk in synchronous steps. However the graph is unlabelled and the agents have no means of marking the nodes of the graph and cannot communicate with or see each other until they meet at a node. When the graph is very large we want the time to rendezvous to be independent of the graph size and to depend only on the initial distance between the agents and some local parameters such as the degree of the vertices, and the size of the agent’s label. It is well known that even for simple graphs of degree Δ, the rendezvous time can be exponential in Δ in the worst case. In this paper, we introduce a new version of the rendezvous problem where the agents are equipped with a device that measures its distance to the other agent after every step. We show that these distance-aware agents are able to rendezvous in any unknown graph, in time polynomial in all the local parameters such the degree of the nodes, the initial distance D and the size of the smaller of the two agent labels l =  min (l1, l2). Our algorithm has a time complexity of O(Δ(D + logl)) and we show an almost matching lower bound of Ω(Δ(D + logl/logΔ)) on the time complexity of any rendezvous algorithm in our scenario. Further, this lower bound extends existing lower bounds for the general rendezvous problem without distance awareness.


Mobile Agent Rendezvous Synchronous Anonymous Networks Distance Oracle Lower Bounds 


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Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Shantanu Das
    • 1
  • Dariusz Dereniowski
    • 2
  • Adrian Kosowski
    • 3
    • 4
  • Przemysław Uznański
    • 1
  1. 1.LIFAix-Marseille University and CNRSMarseilleFrance
  2. 2.Dept. of Algorithms and System ModelingGdańsk University of TechnologyGdańskPoland
  3. 3.GANG ProjectInria ParisFrance
  4. 4.LIAFAParis Diderot University and CNRSFrance

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