DISC 2018 · 32nd International Symposium on Distributed Computing, New Orleans, USA, October 2018 · doi:10.4230/LIPIcs.DISC.2018.9
The landscape of the distributed time complexity is nowadays well-understood for subpolynomial complexities. When we look at deterministic algorithms in the LOCAL model and locally checkable problems (LCLs) in bounded-degree graphs, the following picture emerges:
However, the high end of the complexity spectrum was left open by prior work. In general graphs there are problems with complexities of the form $\Theta(n^\alpha)$ for any rational $0 < \alpha \le 1/2$, while for trees only complexities of the form $\Theta(n^{1/k})$ are known. No LCL problem with complexity between $\omega(\sqrt{n})$ and $o(n)$ is known, and neither are there results that would show that such problems do not exist. We show that:
Put otherwise, we show that any LCL with a complexity $o(n)$ can be solved in time $O(\sqrt{n})$ in trees, while the same is not true in general graphs.
Ulrich Schmid and Josef Widder (Eds.): 32nd International Symposium on Distributed Computing (DISC 2018), volume 121 of Leibniz International Proceedings in Informatics (LIPIcs), pages 9:1–9:16, Schloss Dagstuhl–Leibniz-Zentrum für Informatik, 2018
ISBN 978-3-95977-092-7