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arXiv 0904.4903math.STstat.TH
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网络上的迭代极大似然

Iterative Maximum Likelihood on Networks

Elchanan Mossel, Omer Tamuz

摘要:

我们考虑n个代理商位于一个连通图的顶点上。每个代理v接收信号X_v(0)~N(s,1),其中s是未知量。估计s的自然迭代方法是执行以下过程。在迭代t + 1,设X_v(t + 1)是X_v(t)和X_w(t)在v的所有邻居w中的平均值。本文考虑了简单迭代平均的一种变体,它模拟了智能体的“贪婪”行为。在迭代t,每个代理v向其所有邻居声明其估计量X_v(t)的值。然后,它通过取s的最大似然(或最小方差)估计来更新X_v(t + 1),给定V的所有邻居w的X_v(t)和X_w(t),以及图的结构。我们给出了计算X_v(t)的一个显式有效方法,研究了当t趋于无穷大时该方法的收敛性,并证明了如果极限存在,则它对所有v和w都是相同的。对于在传递群作用下对称的图,我们证明了这个过程是有效的。最后,我们表明,贪婪的过程是在某些情况下比简单的平均更有效,而在其他情况下,反之亦然,所以,在这个模型中,“贪婪”的个人代理可能会或可能不会产生不利影响的结果。这里讨论的模型可以被视为贝叶斯经济学中研究的模型的最大似然版本。ML变体更容易获得,并且特别允许显示使用代理网络的估计器的效率中的对称性的重要性。

英文摘要:

We consider n agents located on the vertices of a connected graph. Each agent v receives a signal X_v(0)~N(s, 1) where s is an unknown quantity. A natural iterative way of estimating s is to perform the following procedure. At iteration t + 1 let X_v(t + 1) be the average of X_v(t) and of X_w(t) among all the neighbors w of v. In this paper we consider a variant of simple iterative averaging, which models "greedy" behavior of the agents. At iteration t, each agent v declares the value of its estimator X_v(t) to all of its neighbors. Then, it updates X_v(t + 1) by taking the maximum likelihood (or minimum variance) estimator of s, given X_v(t) and X_w(t) for all neighbors w of v, and the structure of the graph. We give an explicit efficient procedure for calculating X_v(t), study the convergence of the process as t goes to infinity and show that if the limit exists then it is the same for all v and w. For graphs that are symmetric under actions of transitive groups, we show that the process is efficient. Finally, we show that the greedy process is in some cases more efficient than simple averaging, while in other cases the converse is true, so that, in this model, "greed" of the individual agents may or may not have an adverse affect on the outcome. The model discussed here may be viewed as the Maximum-Likelihood version of models studied in Bayesian Economics. The ML variant is more accessible and allows in particular to show the significance of symmetry in the efficiency of estimators using networks of agents.

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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