TY - GEN

T1 - Caching with time windows

AU - Gupta, Anupam

AU - Kumar, Amit

AU - Panigrahi, Debmalya

N1 - Publisher Copyright:
© 2020 ACM.

PY - 2020/6/8

Y1 - 2020/6/8

N2 - 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.

AB - 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.

KW - Approximation algorithms

KW - Online caching

UR - http://www.scopus.com/inward/record.url?scp=85086758893&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85086758893&partnerID=8YFLogxK

U2 - 10.1145/3357713.3384277

DO - 10.1145/3357713.3384277

M3 - Conference contribution

AN - SCOPUS:85086758893

T3 - Proceedings of the Annual ACM Symposium on Theory of Computing

SP - 1125

EP - 1138

BT - STOC 2020 - Proceedings of the 52nd Annual ACM SIGACT Symposium on Theory of Computing

A2 - Makarychev, Konstantin

A2 - Makarychev, Yury

A2 - Tulsiani, Madhur

A2 - Kamath, Gautam

A2 - Chuzhoy, Julia

PB - Association for Computing Machinery

T2 - 52nd Annual ACM SIGACT Symposium on Theory of Computing, STOC 2020

Y2 - 22 June 2020 through 26 June 2020

ER -