Caching with time windows

Conference Paper

We consider the (weighted) Paging with Time Windows problem, which is identical to the classical weighted paging problem but where each page request only needs to be served by a given deadline. This problem arises in many practical applications of online caching, such as the deadline I/O scheduler in the Linux kernel and video-on-demand streaming. From a theoretical perspective, this generalizes the caching problem to allow delayed service, a line of work that has recently gained traction in online algorithms (e.g., Emek et al. STOC '16, Azar et al. STOC '17, Azar and Touitou FOCS '19, etc.). Our main result is an O(log k log n)-competitive algorithm for the Paging with Time Windows problem on n pages with a cache of size k. This significantly improves on the previous best bound of O(k) (Azar et al. (STOC '17). We also consider the offline version of this problem, for which we give an O(1) approximation algorithm and prove APX-hardness. These are the first results for the offline problem; even NP-hardness was not known before our work. At the heart of our algorithms is a novel hitting-set LP relaxation of this problem that overcomes the Omega(k) integrality gap of the natural LP for the problem. To the best of our knowledge, this is the first example of an LP-based algorithm for an online algorithm with delays/deadlines.

Full Text

Duke Authors

Cited Authors

  • Gupta, A; Kumar, A; Panigrahi, D

Published Date

  • June 8, 2020

Published In

Start / End Page

  • 1125 - 1138

International Standard Serial Number (ISSN)

  • 0737-8017

International Standard Book Number 13 (ISBN-13)

  • 9781450369794

Digital Object Identifier (DOI)

  • 10.1145/3357713.3384277

Citation Source

  • Scopus