Title
A Tight Analysis of the Parallel Undecided-State Dynamics with Two Colors.
Abstract
The emph{Undecided-State Dynamics} is a well-known protocol for distributed consensus. We analyze it in the parallel pull communication model on the complete graph for the emph{binary} case (every node can either support one of emph{two} possible colors, or be in the undecided state). An interesting open question is whether this dynamics emph{always} (i.e., starting from an arbitrary initial configuration) reaches consensus emph{quickly} (i.e., within a polylogarithmic number of rounds) in a complete graph with $n$ nodes. Previous work in this setting only considers initial color configurations with no undecided nodes and a large emph{bias} (i.e., $Theta(n)$) towards the majority color. In this paper we present an textit{unconditional} analysis of the Undecided-State Dynamics that answers to the above question in the affirmative. We prove that, starting from textit{any} initial configuration, the process reaches a monochromatic configuration within $O(log n)$ rounds, with high probability. This bound turns out to be tight. Our analysis also shows that, if the initial configuration has bias $Omega(sqrt{nlog n})$, then the dynamics converges toward the initial majority color, with high probability.
Year
Venue
Field
2018
MFCS
Consensus,Discrete mathematics,Complete graph,Binary logarithm,Monochromatic color,Combinatorics,Computer science,Models of communication,Omega,Time complexity,Binary number
DocType
Citations 
PageRank 
Conference
1
0.35
References 
Authors
0
6
Name
Order
Citations
PageRank
Andrea E. F. Clementi1116885.30
Mohsen Ghaffari245244.89
Luciano Gualà312119.25
Emanuele Natale47414.52
Francesco Pasquale542128.22
Giacomo Scornavacca643.43