Abstract
In the stabilizing consensus problem each agent of a networked system has an input value and is repeatedly writing an output value; it is required that eventually all the output values stabilize to the same value which, moreover, must be one of the input values. We study this problem for a synchronous model with identical and anonymous agents that are connected by a time-varying topology and may join the system at any time (asynchronous start). Our main result is a generic MinMax algorithm that solves the stabilizing consensus problem in this model when, in each sufficiently long but bounded period of time, there is an agent, called a root, that can send messages, possibly indirectly, to all other agents. We stress that the bound on the time required for achieving this rootedness property is unknown to the agents. Such topologies are highly dynamic (in particular, roots may change arbitrarily over time) and may have very weak connectivity properties (an agent may be never a root). Our distributed MinMax algorithms thus require neither central control nor any global information and are also quite efficient in terms of message size and storage requirements.
Similar content being viewed by others
Notes
To simplify notations, there are self-loops at all nodes of \(\mathbb {G}^{{\mathrm {a}}}(t)\), including those corresponding to the passive agents at round t.
This condition holds if \(\mathbb {G}\) is permanently strongly connected, or if \(\mathbb {G}(t) =G\) for some rooted digraph G and for every positive integer t.
Observe that the network model consisting of all dynamic graphs with non-empty kernel is not closed.
References
Afek, Y., Gafni, E.: Asynchrony from synchrony. In: International Conference on Distributed Computing and Networking, pp. 225–239. Springer, Berlin (2013)
Alpern, B., Schneider, F.B.: Defining liveness. Inf. Process. Lett. 21(4), 181–185 (1985)
Angluin, D., Fischer, M.J., Jiang, H.: Stabilizing consensus in mobile networks. In: Gibbons, P.B., Abdelzaher, T., Aspnes, J., Rao, R. (eds.) Distributed Computing in Sensor Systems. Lecture Notes in Computer Science, vol. 4026, pp. 37–50. Springer, Berlin (2006)
Becchetti, L., Clementi, A., Natale, E., Pasquale, F., Trevisan, L.: Stabilizing consensus with many opinions. In: Proceedings of the Twenty-seventh Annual ACM-SIAM Symposium on Discrete Algorithms, SODA ’16, pp. 620–635, Philadelphia, PA, USA. Society for Industrial and Applied Mathematics (2016)
Bertsekas, D.P., Tsitsiklis, J.N.: Parallel and Distributed Computation: Numerical Methods. Athena Scientific, Belmont (1989)
Blondel, V.D., Hendrickx, J.M., Olshevsky, A., Tsitsiklis, J.N.: Convergence in multiagent coordination, consensus, and flocking. In: Proceedings of the 44th IEEE Conference on Decision and Control, and the European Control Conference (CDC-ECC), pp. 2996–3000. IEEE, New York, NY (2005)
Cao, M., Stephen, M.A., Anderson, B.D.O.: Reaching a consensus in a dynamically changing environment: a graphical approach. SIAM J. Control Optim. 47(2), 575–600 (2008)
Casteigts, A., Flocchini, P., Quattrociocchi, W., Santoro, N.: Time-varying graphs and dynamic networks. Int. J. Parallel Emerg. Distrib. Syst. 27(5), 387–408 (2012)
Charron-Bost, B., Függer, M., Nowak, T.: Approximate consensus in highly dynamic networks: the role of averaging algorithms. In: Proceedings of the 42nd International Colloquium on Automata, Languages, and Programming, ICALP15, pp. 528–539 (2015)
Charron-Bost, B., Moran, S.: The firing squad problem revisited. In: Rolf, N., Brigitte, V. (eds), 35th Symposium on Theoretical Aspects of Computer Science (STACS 2018), Volume 96 of Leibniz International Proceedings in Informatics (LIPIcs), pp. 20:1–20:14 (2018)
Charron-Bost, B., Schiper, A.: The Head-Of model: computing in distributed systems with benign faults. Distrib. Comput. 22(1), 49–71 (2009)
Coulouma, É., Godard, E., Peters, J.: A characterization of oblivious message adversaries for which consensus is solvable. Theor. Comput. Sci. 584, 80–90 (2015)
Doerr, B., Goldberg, L.A., Minder, L., Sauerwald, T., Scheideler, C.: Stabilizing consensus with the power of two choices. In: Proceedings of the Twenty-third Annual ACM Symposium on Parallelism in Algorithms and Architectures, SPAA ’11, pp. 149–158, New York, NY, USA (2011)
Jadbabaie, A., Lin, J., Stephen, M.A.: Coordination of groups of mobile autonomous stability agents using nearest neighbor rules. IEEE Trans. Autom. Control 48(6), 988–1001 (2003)
Lorenz, D.A., Lorenz, J.: Convergence to consensus by general averaging. In: Bru, R., Romero-Vivó, S. (eds.) Positive Systems, Volume 389 of Lecture Notes in Control and Information Sciences, pp. 91–99. Springer, Berlin (2009)
Lubitch, R., Moran, S.: Closed schedulers: a novel technique for analyzing asynchronous protocols. Distrib. Comput. 8(4), 203–210 (1995)
Lynch, N.A.: Distributed Algorithms. Morgan Kaufmann, San Francisco (1996)
Moran, S.: Averaging and rounding cannot achieve stabilizing consensus in rooted dynamic graphs. Unpublished note (2020). Available at https://www.dropbox.com/s/h08myw1hupruxwg/AC-not-SC2002.pdf?dl=0
Moreau, L.: Stability of multiagent systems with time-dependent communication links. IEEE Trans. Autom. Control 50(2), 169–182 (2005)
Olfati-Saber, R., Fax, J.A., Murray, R.M.: Consensus and cooperation in networked multi-agent systems. Proc. IEEE 95(1), 215–233 (2007)
Olshevsky, A., Tsitsiklis, J.N.: Convergence speed in distributed consensus and averaging. SIAM Rev. 53(4), 747–772 (2011)
Santoro, N., Widmayer, P.: Time is not a healer. In: Proceedings of the 6th Symposium on Theoretical Aspects of Computer Science, pp. 304–313, Paderborn, Germany (1989)
Vicsek, T., Czirók, A., Ben-Jacob, E., Cohen, I., Shochet, O.: Novel type of phase transition in a system of self-driven particles. Phys. Rev. Lett. 75(6), 1226–1229 (1995)
Winkler, K., Schmid, U., Moses, Y.: A characterization of consensus solvability for closed message adversaries. In: 23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Schloss Dagstuhl-Leibniz-Zentrum für Informatik (2020)
Acknowledgements
We would like to thank the anonymous referees for their helpful comments.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Charron-Bost, B., Moran, S. MinMax algorithms for stabilizing consensus. Distrib. Comput. 34, 195–206 (2021). https://doi.org/10.1007/s00446-021-00392-9
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00446-021-00392-9