Cut Query Algorithms with Star ContractionShow others and affiliations
2022 (English)In: 2022 IEEE 63RD ANNUAL SYMPOSIUM ON FOUNDATIONS OF COMPUTER SCIENCE (FOCS), Institute of Electrical and Electronics Engineers (IEEE) , 2022, p. 507-518Conference paper, Published paper (Refereed)
Abstract [en]
We study the complexity of determining the edge connectivity of a simple graph with cut queries. We show that (i) there is a bounded-error randomized algorithm that computes edge connectivity with O(n) cut queries, and (ii) there is a bounded-error quantum algorithm that computes edge connectivity with (O) over tilde(root n) cut queries. To prove these results we introduce a new technique, called star contraction, to randomly contract edges of a graph while preserving non-trivial minimum cuts. In star contraction vertices randomly contract an edge incident on a small set of randomly chosen "center" vertices. In contrast to the related 2-out contraction technique of Ghaffari, Nowicki, and Thorup [SODA'20], star contraction only contracts vertex-disjoint star subgraphs, which allows it to be efficiently implemented via cut queries. The O(n) bound from item (i) was not known even for the simpler problem of connectivity, and it improves the O(n log(3) n) upper bound by Rubinstein, Schramm, and Weinberg [ITCS'18]. The bound is tight under the reasonable conjecture that the randomized communication complexity of connectivity is Omega(n log n), an open question since the seminal work of Babai, Frankl, and Simon [FOCS'86]. The bound also excludes using edge connectivity on simple graphs to prove a superlinear randomized query lower bound for minimizing a symmetric submodular function. The quantum algorithm from item (ii) gives a nearlyquadratic separation with the randomized complexity, and addresses an open question of Lee, Santha, and Zhang [SODA'21]. The algorithm can alternatively be viewed as computing the edge connectivity of a simple graph with (O) over tilde(root n) matrix-vector multiplication queries to its adjacency matrix. Finally, we demonstrate the use of star contraction outside of the cut query setting by designing a one-pass semi-streaming algorithm for computing edge connectivity in the complete vertex arrival setting. This contrasts with the edge arrival setting where two passes are required.
Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE) , 2022. p. 507-518
Series
Annual IEEE Symposium on Foundations of Computer Science, ISSN 0272-5428
Keywords [en]
F.1.1 Models of Computation, F.1.3 Complexity Measures and Classes, F.2 Analysis of Algorithms and Problem Complexity
National Category
Computer Sciences
Identifiers
URN: urn:nbn:se:kth:diva-336858DOI: 10.1109/FOCS54457.2022.00055ISI: 000909382900047Scopus ID: 2-s2.0-85146357491OAI: oai:DiVA.org:kth-336858DiVA, id: diva2:1800292
Conference
63rd Annual IEEE Symposium on Foundations of Computer Science (FOCS), OCT 31-NOV 03, 2022, Denver, CO, United States of America
Note
Part of proceedings ISBN 978-1-6654-5519-0
QC 20230927
2023-09-262023-09-262024-07-23Bibliographically approved