Constructing light spanners deterministically in near-linear time

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Graph spanners are well-studied and widely used both in theory and practice. In a recent breakthrough, Chechik and Wulff-Nilsen [10] improved the state-of-the-art for light spanners by constructing a (2k−1)(1+ε)-spanner with [Formula presented] edges and [Formula presented] lightness. Soon after, Filtser and Solomon [18] showed that the classic greedy spanner construction achieves the same bounds. The major drawback of the greedy spanner is its running time of [Formula presented] (which is faster than [10]). This makes the construction impractical even for graphs of moderate size. Much faster spanner constructions do exist but they only achieve lightness [Formula presented], even when randomization is used. The contribution of this paper is deterministic spanner constructions that are fast, and achieve similar bounds as the state-of-the-art slower constructions. Our first result is an [Formula presented] time spanner construction which achieves the state-of-the-art bounds. Our second result is an Oε(m+nlog⁡n) time construction of a spanner with (2k−1)(1+ε) stretch, [Formula presented] edges and [Formula presented] lightness. This is an exponential improvement in the dependence on k compared to the previous result with such running time. Finally, for the important special case where k=log⁡n, for every constant ε>0, we provide an O(m+n1+ε) time construction that produces an O(log⁡n)-spanner with O(n) edges and O(1) lightness which is asymptotically optimal. This is the first known sub-quadratic construction of such a spanner for any k=ω(1). To achieve our constructions, we show a novel deterministic incremental approximate distance oracle. Our new oracle is crucial in our construction, as known randomized dynamic oracles require the assumption of a non-adaptive adversary. This is a strong assumption, which has seen recent attention in prolific venues. Our new oracle allows the order of the edge insertions to not be fixed in advance, which is critical as our spanner algorithm chooses which edges to insert based on the answers to distance queries. We believe our new oracle is of independent interest.

OriginalsprogEngelsk
TidsskriftTheoretical Computer Science
Vol/bind907
Sider (fra-til)82-112
ISSN0304-3975
DOI
StatusUdgivet - 12 mar. 2022

Bibliografisk note

Funding Information:
Research partly supported by investigator Grant 16582, Basic Algorithms Research Copenhagen (BARC), from the VILLUM Foundation.Research partly supported by Advanced Grant DFF-0602-02499B from the Danish Council for Independent Research.Supported in part by the Simons Foundation, ISF grant No. (1817/17), and by BSF grant No. 2015813. The research was done while the author was affiliated with Ben-Gurion University of the Negev, and Columbia University.Research partly supported by Villum Fonden grant 16582.Research partly supported by the Starting Grant 7027-00050B from the Independent Research Fund Denmark under the Sapere Aude research career programme.

Publisher Copyright:
© 2022 Elsevier B.V.

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