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Optimal projective algorithms for the list update problem

Ambuehl, Christoph, Gaertner, Bernd and von Stengel, Bernhard (2010) Optimal projective algorithms for the list update problem. arXiv.org.

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Abstract

The list update problem is a classical online problem, with an optimal competitive ratio that is still open, known to be somewhere between 1.5 and 1.6. An algorithm with competitive ratio 1.6, the smallest known to date, is COMB, a randomized combination of BIT and TIMESTAMP(0). This and many other known algorithms, like MTF, are projective in the sense that they can be defined by looking only at any pair of list items at a time. Projectivity simplifies both the description of the algorithm and its analysis, and so far seems to be the only way to define a good online algorithm for lists of arbitrary length. In this paper we characterize all projective list update algorithms and show that their competitive ratio is never smaller than 1.6 in the partial cost model. Therefore, COMB is a best possible projective algorithm in this model.

Item Type: Monograph (Technical Report)
Official URL: http://arxiv.org/
Additional Information: © 2010 The authors
Library of Congress subject classification: Q Science > QA Mathematics
Sets: Departments > Mathematics
Rights: http://www.lse.ac.uk/library/usingTheLibrary/academicSupport/OA/depositYourResearch.aspx
Date Deposited: 23 Jan 2012 16:07
URL: http://eprints.lse.ac.uk/41656/

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