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Competitive Algorithms for Generalized k-Server in Uniform Metrics
ACM Transactions on Algorithms ( IF 1.3 ) Pub Date : 2023-02-20 , DOI: https://dl.acm.org/doi/10.1145/3568677
Nikhil Bansal, Marek Eliáš, Grigorios Koumoutsos, Jesper Nederlof

The generalized k-server problem is a far-reaching extension of the k-server problem with several applications. Here, each server si lies in its own metric space Mi. A request is a k-tuple r = (r1,r2,… ,rk, which is served by moving some server si to the point ri ∈ Mi, and the goal is to minimize the total distance traveled by the servers. Despite much work, no f(k)-competitive algorithm is known for the problem for k > 2 servers, even for special cases such as uniform metrics and lines.

Here, we consider the problem in uniform metrics and give the first f(k)-competitive algorithms for general k. In particular, we obtain deterministic and randomized algorithms with competitive ratio k · 2k and O(k3 log k), respectively. Our deterministic bound is based on a novel application of the polynomial method to online algorithms, and essentially matches the long-known lower bound of 2k-1. We also give a 22O(k)-competitive deterministic algorithm for weighted uniform metrics, which also essentially matches the recent doubly exponential lower bound for the problem.



中文翻译:

统一度量中广义 k-Server 的竞争算法

广义k -server 问题是k -server 问题的深远扩展,具有多种应用。这里,每个服务器s i位于它自己的度量空间M i中。请求是一个k元组r = ( r 1 , r 2 ,… , r k,它通过将一些服务器s i移动到点r i ∈ M i来服务,目标是最小化通过的总距离服务器。尽管做了很多工作,没有f ( k)-competitive algorithm 以k > 2 服务器的问题而闻名,即使对于统一度量和线路等特殊情况也是如此。

在这里,我们考虑统一度量中的问题,并给出一般k的第一个f ( k ) 竞争算法。特别是,我们分别获得了竞争比为k · 2 kO ( k 3 log k ) 的确定性和随机算法。我们的确定性界限基于多项式方法在在线算法中的新颖应用,并且基本上与众所周知的下界 2 k -1 相匹配。我们还给出 2 2 O(k)- 用于加权统一度量的竞争确定性算法,它也基本上匹配问题的最近双指数下界。

更新日期:2023-02-20
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