Fast Multidimensional Asymptotic and Approximate Consensus

TL;DR

This paper introduces two new algorithms for multidimensional consensus in dynamic networks that achieve faster convergence rates independent of data dimension, improving over previous methods especially in asynchronous Byzantine fault scenarios.

Contribution

The paper presents the first algorithms with contraction rate and time complexity independent of the data dimension for multidimensional consensus in dynamic networks.

Findings

Contraction rate and time complexity are independent of the dimension d.

Improved time complexity from Ω(d log(dΔ/ε)) to O(log(Δ/ε)).

Algorithms handle Byzantine faults in asynchronous message passing systems.

Abstract

We study the problems of asymptotic and approximate consensus in which agents have to get their values arbitrarily close to each others' inside the convex hull of initial values, either without or with an explicit decision by the agents. In particular, we are concerned with the case of multidimensional data, i.e., the agents' values are $d$-dimensional vectors. We introduce two new algorithms for dynamic networks, subsuming classical failure models like asynchronous message passing systems with Byzantine agents. The algorithms are the first to have a contraction rate and time complexity independent of the dimension $d$. In particular, we improve the time complexity from the previously fastest approximate consensus algorithm in asynchronous message passing systems with Byzantine faults by Mendes et al. [Distrib. Comput. 28] from $\Omega\!\left( d \log\frac{d\Delta}{\varepsilon} \right)$ to $O\!\left( \log\frac{\Delta}{\varepsilon} \right)$, where $\Delta$ is the initial and $\varepsilon$ is the terminal diameter of the set of vectors of correct agents.