,
Filippo Casagrande
,
Avinandan Das,
Massimo Equi
,
Henrik Lievonen
,
Augusto Modanese
,
Ronja Stimpert
Creative Commons Attribution 4.0 International license
The online-LOCAL and SLOCAL models are extensions of the LOCAL model where nodes are processed in a sequential but potentially adversarial order. So far, the only problem we know of where the global memory of the online-LOCAL model has an advantage over SLOCAL is 3-coloring bipartite graphs. Recently, Chang et al. [PODC 2024] showed that even in grids, 3-coloring requires Ω(log n) locality in deterministic online-LOCAL. This result was subsequently extended by Akbari et al. [STOC 2025] to also hold in randomized online-LOCAL. However, both proofs heavily rely on the assumption that the algorithm does not have access to the orientation of the underlying grid. In this paper, we show how to lift this requirement and obtain the same lower bound (against either model) even when the algorithm is explicitly given a globally consistent orientation of the grid.
@InProceedings{boudier_et_al:LIPIcs.OPODIS.2025.19,
author = {Boudier, Thomas and Casagrande, Filippo and Das, Avinandan and Equi, Massimo and Lievonen, Henrik and Modanese, Augusto and Stimpert, Ronja},
title = {{Orientation Does Not Help with 3-Coloring a Grid in Online-LOCAL}},
booktitle = {29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
pages = {19:1--19:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-409-3},
ISSN = {1868-8969},
year = {2026},
volume = {361},
editor = {Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.19},
URN = {urn:nbn:de:0030-drops-251925},
doi = {10.4230/LIPIcs.OPODIS.2025.19},
annote = {Keywords: coloring, locally checkable labeling problems, online algorithms}
}