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arXiv 1305.3333cs.GT
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凹成本函数的策略验证设施选址

Strategy-Proof Facility Location for Concave Cost Functions

Dimitris Fotakis, Christos Tzamos

摘要:

我们考虑k-设施位置游戏,其中n个战略代理报告他们的位置上的真正的线,和一个机制将它们映射到k设施。每个代理寻求最小化他的连接成本,由他到最近设施的距离的非负递增函数给出。从以前的工作出发,主要考虑身份成本函数,我们感兴趣的机制,没有支付(组)strategyproof任何给定的成本函数,并实现一个很好的近似比的社会成本和/或代理的最大成本。我们提出了一个随机机制,称为相等的成本,这是组strategyproof,并实现了有界的逼近比为所有的k和n,对于任何给定的凹成本函数。最大成本的近似比最多为2,社会成本的近似比最多为n。据我们所知,这是第一个机制,具有k > 2设施和任何数量的代理的实例的有界近似比。我们的结果意味着一个有趣的确定性机制之间的分离,其近似比最大成本从2跳跃到无界时,k从2增加到3,和随机机制,其近似比保持在所有k最多为2。在消极的一面,我们排除了一个机制的可能性与严格凸成本函数的属性相等的成本。我们还提出了一个随机机制,称为挑选失败者,它适用于实例与k设施和n = k+1代理,并为任何给定的凹成本函数,是强组strategyproof,并实现了近似比为2的社会成本。

英文摘要:

We consider k-Facility Location games, where n strategic agents report their locations on the real line, and a mechanism maps them to k facilities. Each agent seeks to minimize his connection cost, given by a nonnegative increasing function of his distance to the nearest facility. Departing from previous work, that mostly considers the identity cost function, we are interested in mechanisms without payments that are (group) strategyproof for any given cost function, and achieve a good approximation ratio for the social cost and/or the maximum cost of the agents. We present a randomized mechanism, called Equal Cost, which is group strategyproof and achieves a bounded approximation ratio for all k and n, for any given concave cost function. The approximation ratio is at most 2 for Max Cost and at most n for Social Cost. To the best of our knowledge, this is the first mechanism with a bounded approximation ratio for instances with k > 2 facilities and any number of agents. Our result implies an interesting separation between deterministic mechanisms, whose approximation ratio for Max Cost jumps from 2 to unbounded when k increases from 2 to 3, and randomized mechanisms, whose approximation ratio remains at most 2 for all k. On the negative side, we exclude the possibility of a mechanism with the properties of Equal Cost for strictly convex cost functions. We also present a randomized mechanism, called Pick the Loser, which applies to instances with k facilities and n = k+1 agents, and for any given concave cost function, is strongly group strategyproof and achieves an approximation ratio of 2 for Social Cost.

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