eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2017-10-12
51:1
51:3
10.4230/LIPIcs.DISC.2017.51
article
Brief Announcement: Lower Bounds for Asymptotic Consensus in Dynamic Networks
Függer, Matthias
Nowak, Thomas
Schwarz, Manfred
In this work we study the performance of asymptotic and approximate consensus algorithms in dynamic networks. The asymptotic consensus problem requires a set of agents to repeatedly set their outputs such that the outputs converge to a common value within the convex hull of initial values. This problem, and the related approximate consensus problem, are fundamental building blocks in distributed systems where exact consensus among agents is not required, e.g., man-made distributed control systems, and have applications in the analysis of natural distributed systems, such as flocking and opinion dynamics. We prove new nontrivial lower bounds on the contraction rates of asymptotic consensus algorithms, from which we deduce lower bounds on the time complexity of approximate consensus algorithms. In particular, the obtained bounds show optimality of asymptotic and approximate consensus algorithms presented in [Charron-Bost et al., ICALP'16] for certain classes of networks that include classical failure assumptions, and confine the search for optimal bounds in the general case.
Central to our lower bound proofs is an extended notion of valency, the set of reachable limits of an asymptotic consensus algorithm starting from a given configuration. We further relate topological properties of valencies to the solvability of exact consensus, shedding some light on the relation of these three fundamental problems in dynamic networks.
https://drops.dagstuhl.de/storage/00lipics/lipics-vol091-disc2017/LIPIcs.DISC.2017.51/LIPIcs.DISC.2017.51.pdf
Asymptotic Consensus
Dynamic Networks
Contraction Rate
Time Commplexity
Lower Bounds