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What and Who
Title:Weighted k-Server Bounds via Combinatorial Dichotomies
Speaker:Grigorios Koumoutsos
coming from:Max-Planck-Institut für Informatik - D1
Speakers Bio:
Event Type:AG1 Mittagsseminar (own work)
Visibility:D1, D2, D3, D4, D5, RG1, SWS, MMCI
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Level:AG Audience
Language:English
Date, Time and Location
Date:Tuesday, 6 March 2018
Time:13:00
Duration:30 Minutes
Location:Saarbrücken
Building:E1 4
Room:024
Abstract
 

The weighted k-server problem is a natural generalization of the k-server problem where each server has a different weight. We consider the problem on uniform metrics, which corresponds to a natural generalization of paging. Our main result is a doubly exponential lower bound on the competitive ratio of any deterministic online algorithm, that essentially matches the known upper bounds for the problem and closes a large and long-standing gap.

The lower bound is based on relating the weighted k-server problem to a certain combinatorial problem and proving a Ramsey-theoretic lower bound for it. This combinatorial connection also reveals several structural properties of low cost feasible solutions to serve a sequence of requests. We use this to show that the generalized Work Function Algorithm achieves an almost optimum competitive ratio, and to obtain new refined upper bounds on the competitive ratio for the case of d different weight classes.


Joint work with Nikhil Bansal and Marek Elias, appeared in FOCS 2017.

Contact
Name(s):Yun Kuen Cheung
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Created:
Yun Kuen Cheung, 03/02/2018 03:13 PM
Last modified:
Uwe Brahm/MPII/DE, 03/06/2018 07:01 AM
  • Yun Kuen Cheung, 03/02/2018 03:13 PM -- Created document.