Observe and remain silent (communication-less agent location discovery)

Tom Friedetzky, Leszek Ga̧sieniec, Thomas Gorry, Russell Martin

Research output: Chapter in Book/Report/Conference proceedingConference contribution

9 Scopus citations


We study a randomised distributed communication-less coordination mechanism for n uniform anonymous agents located on a circle with unit circumference. We assume the agents are located at arbitrary but distinct positions, unknown to other agents. The agents perform actions in synchronised rounds. At the start of each round an agent chooses the direction of its movement (clockwise or anticlockwise), and moves at unit speed during this round. Agents are not allowed to overpass, i.e., when an agent collides with another it instantly starts moving with the same speed in the opposite direction. Agents cannot leave marks on the ring, have zero vision and cannot exchange messages. However, on the conclusion of each round each agent has access to (some, not necessarily all) information regarding its trajectory during this round. This information can be processed and stored by the agent for further analysis. The location discovery task to be performed by each agent is to determine the initial position of every other agent and eventually to stop at its initial position, or proceed to another task, in a fully synchronised manner. Our primary motivation is to study distributed systems where agents collect the minimum amount of information that is necessary to accomplish this location discovery task. Our main result is a fully distributed randomised (Las Vegas type) algorithm, solving the location discovery problem w.h.p. in O(nlog 2 n) rounds (assuming the agents collect sufficient information). Note that our result also holds if initially the agents do not know the value of n and they have no coherent sense of direction.

Original languageEnglish (US)
Title of host publicationMathematical Foundations of Computer Science 2012 - 37th International Symposium, MFCS 2012, Proceedings
Number of pages12
StatePublished - 2012
Externally publishedYes
Event37th International Symposium on Mathematical Foundations of Computer Science 2012, MFCS 2012 - Bratislava, Slovakia
Duration: Aug 27 2012Aug 31 2012

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume7464 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference37th International Symposium on Mathematical Foundations of Computer Science 2012, MFCS 2012

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


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