Partial Gathering of Mobile Agents Without Identifiers or Global Knowledge in Asynchronous Unidirectional Rings

  • Masahiro ShibataEmail author
  • Norikazu Kawata
  • Yuichi Sudo
  • Fukuhito Ooshita
  • Hirotsugu Kakugawa
  • Toshimitsu Masuzawa
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11639)


In this paper, we consider the partial gathering problem of mobile agents in asynchronous unidirectional rings. This problem requires that, for a given positive integer g, all the agents terminate in a configuration such that at least g agents or no agent exist at each node. While the previous work achieves move-optimal partial gathering using distinct IDs or knowledge of the number of agents, in this paper we aim to achieve this without such information. We consider deterministic and randomized cases. First, in the deterministic case, we show that unsolvable initial configurations exist. In addition, we propose an algorithm to solve the problem from any solvable initial configuration in O(gn) total number of moves, where n is the number of nodes. Next, in the randomized case, we propose an algorithm to solve the problem in O(gn) expected total number of moves from any initial configuration. Since agents require \(\varOmega (gn)\) total number of moves to solve the partial gathering problem, our algorithms can solve the problem in asymptotically optimal total number of moves without global knowledge.


Distributed system Mobile agent Gathering problem Partial gathering 



This work was partially supported by JSPS KAKENHI Grant Number 17K19977, 18K18000, 18K11167, 18K18031, and 19K11826, and Japan Science and Technology Agency (JST) SICORP.


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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Masahiro Shibata
    • 1
    Email author
  • Norikazu Kawata
    • 2
  • Yuichi Sudo
    • 2
  • Fukuhito Ooshita
    • 3
  • Hirotsugu Kakugawa
    • 4
  • Toshimitsu Masuzawa
    • 2
  1. 1.Graduate School of Computer Science and Systems EngineeringKyushu Institute of TechnologyIizukaJapan
  2. 2.Graduate School of Information Science and TechnologyOsaka UniversitySuitaJapan
  3. 3.Graduate School of Science and TechnologyNAISTIkomaJapan
  4. 4.Faculty of Science and TechnologyRyukoku UniversityOotsuJapan

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