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arXiv 0907.2049cs.GTcs.MA
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网络定位的防策略近似机制

Strategyproof Approximation Mechanisms for Location on Networks

Noga Alon, Michal Feldman, Ariel D. Procaccia, Moshe Tennenholtz

摘要:

我们考虑的问题,定位设施的网络,表示为一个图。一组战略代理人有不同的理想位置的设施;代理人的成本是其理想位置和设施之间的距离。一种机制将代理人报告的位置映射到设施的位置。具体来说,我们感兴趣的是不使用支付的社会选择机制。我们希望设计防策略的机制,在这个意义上,代理人永远不会受益于说谎,或者,甚至更好的是,群体防策略,在这个意义上,代理人的联盟不能都受益于说谎。同时,我们的机制必须提供一个小的近似比相对于两个优化目标之一:社会成本或最大成本。我们给出了一个几乎完整的表征下的目标函数,确定性和随机机制,并就不同的网络拓扑结构的可行的真实近似比。我们的主要结果是:我们证明了一个简单的随机机制是群体策略防护的,并给出了一个(2-2/n)-近似的社会成本,其中n是代理的数量,当网络是一个圆圈(在计算机网络的情况下称为环);我们设计了一种新的“混合”防策略随机化机制,当网络是圆时,该机制为最大成本提供了3/2的紧近似比;并且我们证明了,即使当网络是树时,也没有随机SP机制可以提供比2-o(1)更好的最大成本的近似比,从而匹配平凡的上限2。

英文摘要:

We consider the problem of locating a facility on a network, represented by a graph. A set of strategic agents have different ideal locations for the facility; the cost of an agent is the distance between its ideal location and the facility. A mechanism maps the locations reported by the agents to the location of the facility. Specifically, we are interested in social choice mechanisms that do not utilize payments. We wish to design mechanisms that are strategyproof, in the sense that agents can never benefit by lying, or, even better, group strategyproof, in the sense that a coalition of agents cannot all benefit by lying. At the same time, our mechanisms must provide a small approximation ratio with respect to one of two optimization targets: the social cost or the maximum cost. We give an almost complete characterization of the feasible truthful approximation ratio under both target functions, deterministic and randomized mechanisms, and with respect to different network topologies. Our main results are: We show that a simple randomized mechanism is group strategyproof and gives a (2-2/n)-approximation for the social cost, where n is the number of agents, when the network is a circle (known as a ring in the case of computer networks); we design a novel "hybrid" strategyproof randomized mechanism that provides a tight approximation ratio of 3/2 for the maximum cost when the network is a circle; and we show that no randomized SP mechanism can provide an approximation ratio better than 2-o(1) to the maximum cost even when the network is a tree, thereby matching a trivial upper bound of two.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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