Replication | Variations on a ThemeRudolf Fleischer ? Steve
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چکیده
We study the online page replication problem. We present a new randomized algorithm for rings which is 2.37297-competitive, improving the best previous result of 3.16395. We also show that no randomized algorithm is better than 1.75037-competitive on the ring. This is the rst non-trivial lower bound for the problem. We initiate the study of replication in continuous metric spaces (the Nomads' Problem). Deterministic algorithms in continuous metric spaces correspond naturally to randomized algorithms in discrete metric spaces with the same competitive ratio. We give a 1.58198-competitive deterministic algorithm for continuous trees and a 2.54150-competitive deterministic algorithm for continuous rings. These algorithms correspond to the randomized discrete algorithms by Albers and Koga 2] and GG lazek 12], respectively, but our proofs are much simpler. We also show a deterministic lower bound of 2.31023 for continuous rings. In their seminal paper about the page replication problem, Black and Sleator claim that 2.5 is a lower bound for \the four node cycle", but give no proof. We give evidence against their claim, showing an upper bound of 2.36603 for the ring with four evenly spaced nodes.
منابع مشابه
New results for online page replication
We study the online page replication problem. We present a new randomized online algorithm for rings which is 2.37297-competitive, improving the best previous result of 3.16396. We also show that no randomized online algorithm is better than 1.75037-competitive on the ring; previously, only a 1.58198 bound for a single edge was known. We extend the problem in several new directions: continuous ...
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تاریخ انتشار 1999