Undecided State Dynamics with Many Opinions

Fuente: arXiv
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Auteurs principaux: Cooper, Colin, Mallmann-Trenn, Frederik, Radzik, Tomasz, Shimizu, Nobutaka, Shiraga, Takeharu
Format: Preprint
Publié: 2026
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author Cooper, Colin
Mallmann-Trenn, Frederik
Radzik, Tomasz
Shimizu, Nobutaka
Shiraga, Takeharu
author_facet Cooper, Colin
Mallmann-Trenn, Frederik
Radzik, Tomasz
Shimizu, Nobutaka
Shiraga, Takeharu
contents We study the Undecided-State Dynamics (USD), a fundamental consensus process in which each vertex holds one of $k$ decided opinions or the undecided state. We consider both the gossip model and the population protocol model. Prior work established tight bounds on the consensus time of this process only for the regime $k = O(\sqrt{n}/(\log n)^2)$ (for the population protocol model) and $k = O((n/\log n)^{1/3})$ (for the gossip model), often under restrictive assumptions on the initial configuration. In this paper, we obtain the first consensus-time guarantees for USD that hold for \emph{arbitrary} $2\le k\le n$ and for \emph{arbitrary} initial configurations in both the gossip model and the population protocol model. In the gossip model, USD reaches consensus within $\widetilde O(\min\{k,\sqrt n\})$ synchronous rounds with probability $1-p_{\bot}-n^{-c}$, where $p_{\bot}$ is the gossip-specific probability of collapsing to the all-undecided state in the first round. In the population protocol model, USD reaches consensus within $\widetilde O(\min\{kn,n^{3/2}\})$ asynchronous interactions with high probability. We also present lower bounds that match the upper bounds up to polylogarithmic factors for a specific initial configuration and show that our upper bounds are essentially optimal.
format Preprint
id arxiv_https___arxiv_org_abs_2603_02636
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Undecided State Dynamics with Many Opinions
Cooper, Colin
Mallmann-Trenn, Frederik
Radzik, Tomasz
Shimizu, Nobutaka
Shiraga, Takeharu
Distributed, Parallel, and Cluster Computing
We study the Undecided-State Dynamics (USD), a fundamental consensus process in which each vertex holds one of $k$ decided opinions or the undecided state. We consider both the gossip model and the population protocol model. Prior work established tight bounds on the consensus time of this process only for the regime $k = O(\sqrt{n}/(\log n)^2)$ (for the population protocol model) and $k = O((n/\log n)^{1/3})$ (for the gossip model), often under restrictive assumptions on the initial configuration. In this paper, we obtain the first consensus-time guarantees for USD that hold for \emph{arbitrary} $2\le k\le n$ and for \emph{arbitrary} initial configurations in both the gossip model and the population protocol model. In the gossip model, USD reaches consensus within $\widetilde O(\min\{k,\sqrt n\})$ synchronous rounds with probability $1-p_{\bot}-n^{-c}$, where $p_{\bot}$ is the gossip-specific probability of collapsing to the all-undecided state in the first round. In the population protocol model, USD reaches consensus within $\widetilde O(\min\{kn,n^{3/2}\})$ asynchronous interactions with high probability. We also present lower bounds that match the upper bounds up to polylogarithmic factors for a specific initial configuration and show that our upper bounds are essentially optimal.
title Undecided State Dynamics with Many Opinions
topic Distributed, Parallel, and Cluster Computing
url https://arxiv.org/abs/2603.02636