Diameter-Free Distributed Frequency Control for Graph Coloring in the CONGEST Model

Abstract

This paper presents two randomized proper-coloring algorithms that control color frequencies in the synchronous CONGEST model without paying a diameter-dependent coordination cost. Let $λ\geq 1$ denote the desired failure exponent. For every fixed $δ> 0$, the first algorithm uses $χ= \lceil (2+δ)Δ\rceil$ colors and, with probability at least $1 - n^{-λ}$, outputs a proper coloring that bounds the deviation of every color frequency from $n/χ$ by $O_δ(\sqrt{(λ+1)(n/χ)\lg n} + (λ+1)\lg n)$. Under an explicit load condition, this additive guarantee yields two-sided relative balance. The second algorithm works with every $χ> Δ$ and gives a one-sided frequency cap controlled by the palette slack $χ- Δ$. In particular, it uses $Δ+ \lceil (Δ+1)/\lceil \ln n \rceil \rceil$ colors and caps every used color class by $O((λ+1)(σ\lg^2 n + \lg n))$, where $σ= n/(Δ+1)$. Both algorithms run in $O((λ+1)\lg n)$ rounds, with no dependence on the network diameter; for the first algorithm, the multiplicative constant in the time bound depends on $δ$.