Faster Distributed $Δ$-Coloring via a Reduction to MIS

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Main Authors: Bourreau, Yann, Brandt, Sebastian, Nolin, Alexandre
Format: Preprint
Published: 2025
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author Bourreau, Yann
Brandt, Sebastian
Nolin, Alexandre
author_facet Bourreau, Yann
Brandt, Sebastian
Nolin, Alexandre
contents Recent improvements on the deterministic complexities of fundamental graph problems in the LOCAL model of distributed computing have yielded state-of-the-art upper bounds of $\tilde{O}(\log^{5/3} n)$ rounds for maximal independent set (MIS) and $(Δ+ 1)$-coloring [Ghaffari, Grunau, FOCS'24] and $\tilde{O}(\log^{19/9} n)$ rounds for the more restrictive $Δ$-coloring problem [Ghaffari, Kuhn, FOCS'21; Ghaffari, Grunau, FOCS'24; Bourreau, Brandt, Nolin, STOC'25]. In our work, we show that $Δ$-coloring can be solved deterministically in $\tilde{O}(\log^{5/3} n)$ rounds as well, matching the currently best bound for $(Δ+ 1)$-coloring. We achieve our result by developing a reduction from $Δ$-coloring to MIS that guarantees that the (asymptotic) complexity of $Δ$-coloring is at most the complexity of MIS, unless MIS can be solved in sublogarithmic time, in which case, due to the $Ω(\log n)$-round $Δ$-coloring lower bound from [BFHKLRSU, STOC'16], our reduction implies a tight complexity of $Θ(\log n)$ for $Δ$-coloring. In particular, any improvement on the complexity of the MIS problem will yield the same improvement for the complexity of $Δ$-coloring (up to the true complexity of $Δ$-coloring). Our reduction yields improvements for $Δ$-coloring in the randomized LOCAL model and when complexities are parameterized by both $n$ and $Δ$. We obtain a randomized complexity bound of $\tilde{O}(\log^{5/3} \log n)$ rounds (improving over the state of the art of $\tilde{O}(\log^{8/3} \log n)$ rounds) on general graphs and tight complexities of $Θ(\log n)$ and $Θ(\log \log n)$ for the deterministic, resp.\ randomized, complexity on bounded-degree graphs. In the special case of graphs of constant clique number (which for instance include bipartite graphs), we also give a reduction to the $(Δ+1)$-coloring problem.
format Preprint
id arxiv_https___arxiv_org_abs_2508_01762
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Faster Distributed $Δ$-Coloring via a Reduction to MIS
Bourreau, Yann
Brandt, Sebastian
Nolin, Alexandre
Distributed, Parallel, and Cluster Computing
Data Structures and Algorithms
Recent improvements on the deterministic complexities of fundamental graph problems in the LOCAL model of distributed computing have yielded state-of-the-art upper bounds of $\tilde{O}(\log^{5/3} n)$ rounds for maximal independent set (MIS) and $(Δ+ 1)$-coloring [Ghaffari, Grunau, FOCS'24] and $\tilde{O}(\log^{19/9} n)$ rounds for the more restrictive $Δ$-coloring problem [Ghaffari, Kuhn, FOCS'21; Ghaffari, Grunau, FOCS'24; Bourreau, Brandt, Nolin, STOC'25]. In our work, we show that $Δ$-coloring can be solved deterministically in $\tilde{O}(\log^{5/3} n)$ rounds as well, matching the currently best bound for $(Δ+ 1)$-coloring. We achieve our result by developing a reduction from $Δ$-coloring to MIS that guarantees that the (asymptotic) complexity of $Δ$-coloring is at most the complexity of MIS, unless MIS can be solved in sublogarithmic time, in which case, due to the $Ω(\log n)$-round $Δ$-coloring lower bound from [BFHKLRSU, STOC'16], our reduction implies a tight complexity of $Θ(\log n)$ for $Δ$-coloring. In particular, any improvement on the complexity of the MIS problem will yield the same improvement for the complexity of $Δ$-coloring (up to the true complexity of $Δ$-coloring). Our reduction yields improvements for $Δ$-coloring in the randomized LOCAL model and when complexities are parameterized by both $n$ and $Δ$. We obtain a randomized complexity bound of $\tilde{O}(\log^{5/3} \log n)$ rounds (improving over the state of the art of $\tilde{O}(\log^{8/3} \log n)$ rounds) on general graphs and tight complexities of $Θ(\log n)$ and $Θ(\log \log n)$ for the deterministic, resp.\ randomized, complexity on bounded-degree graphs. In the special case of graphs of constant clique number (which for instance include bipartite graphs), we also give a reduction to the $(Δ+1)$-coloring problem.
title Faster Distributed $Δ$-Coloring via a Reduction to MIS
topic Distributed, Parallel, and Cluster Computing
Data Structures and Algorithms
url https://arxiv.org/abs/2508.01762