Haystack hunting hints and locker room communication

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Abstract

We want to efficiently find a specific object in a large unstructured set, which we model by a randomn-permutation, and we have to do it by revealing just a single element. Clearly, without any help this task is hopeless and the best one can do is to select the element at random, and achieve the success probability 1/n. Can we do better with some small amount of advice about the permutation, even without knowing the target object? We show that by providing advice of just one integer in {0,1,...,n-1}, one can improve the success probability considerably, by a θ(logn/loglogn) factor. We study this and related problems, and show asymptotically matching upper and lower bounds for their optimal probability of success. Our analysis relies on a close relationship of such problems to some intrinsic properties of random permutations related to the rencontres number.

Item Type: Journal Article
Subjects: Q Science > QA Mathematics
Q Science > QA Mathematics > QA76 Electronic computers. Computer science. Computer software
Divisions: Faculty of Science, Engineering and Medicine > Science > Computer Science
Faculty of Science, Engineering and Medicine > Science > Mathematics
Library of Congress Subject Headings (LCSH): Permutations, Mathematical analysis , Computer programming, Algorithms
Journal or Publication Title: Random Structures & Algorithms
Publisher: John Wiley & Sons, Inc.
ISSN: 1042-9832
Official Date: July 2023
Dates:
Date
Event
July 2023
Published
31 August 2022
Available
6 June 2022
Accepted
28 May 2021
Submitted
Volume: 62
Number: 4
Number of Pages: 25
Page Range: pp. 832-856
DOI: 10.1002/rsa.21114
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Open Access (Creative Commons open licence)
Date of first compliant deposit: 19 October 2022
Date of first compliant Open Access: 19 October 2022
RIOXX Funder/Project Grant:
Project/Grant ID
RIOXX Funder Name
Funder ID
UNSPECIFIED
University of Warwick
UNSPECIFIED
IBM Center for the Business of Government
EP/V01305X/1
[EPSRC] Engineering and Physical Sciences Research Council
Doctoral Training Partnership
[EPSRC] Engineering and Physical Sciences Research Council
URI: https://wrap.warwick.ac.uk/170329/

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