,
Adrian Vladu
,
Junyao Zhao
Creative Commons Attribution 4.0 International license
In this paper, we design fixed-parameter tractable (FPT) algorithms for (non-monotone) submodular maximization subject to a matroid constraint, where the matroid rank r is treated as a fixed parameter that is independent of the total number of elements n. We provide two FPT algorithms: one for the offline setting and another for the random-order streaming setting. Our streaming algorithm achieves a 1/2-ε approximation using Õ(r/poly(ε)) memory, while our offline algorithm obtains a 1-(1)/(e)-ε approximation with n⋅ 2^{Õ(r/poly(ε))} runtime and Õ(r/poly(ε)) memory. Both approximation factors are near-optimal in their respective settings, given existing hardness results. In particular, our offline algorithm demonstrates that - unlike in the polynomial-time regime - there is essentially no separation between monotone and non-monotone submodular maximization under a matroid constraint in the FPT framework.
@InProceedings{nematollahi_et_al:LIPIcs.ITCS.2026.105,
author = {Nematollahi, Shamisa and Vladu, Adrian and Zhao, Junyao},
title = {{Fixed-Parameter Tractable Submodular Maximization over a Matroid}},
booktitle = {17th Innovations in Theoretical Computer Science Conference (ITCS 2026)},
pages = {105:1--105:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-410-9},
ISSN = {1868-8969},
year = {2026},
volume = {362},
editor = {Saraf, Shubhangi},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2026.105},
URN = {urn:nbn:de:0030-drops-253924},
doi = {10.4230/LIPIcs.ITCS.2026.105},
annote = {Keywords: Submodular maximization, matroids, parameterized complexity, streaming algorithms}
}