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arXiv 1007.3884cs.AIcs.CCstat.ML
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贝叶斯网络中MAP问题的新结果

New Results for the MAP Problem in Bayesian Networks

Istituto Dalle Molle di Studi sull’Intelligenza Artificiale (IDSIA)(达勒·莫勒人工智能研究所(IDSIA))

Cassio P. de Campos

摘要:

本文提出了新的结果(部分)最大后验概率(MAP)问题的贝叶斯网络,这是问题的查询最可能的状态配置的一些网络变量的证据。首先,它表明,即使在网络非常简单的拓扑结构,如二叉多叉树和简单的树(包括朴素贝叶斯结构)的问题仍然很难。这样的证明扩展了以前的复杂性结果的问题。不可逼近的结果也来自树的情况下,如果每个变量的状态数是没有界的。虽然这个问题被证明是很难的,甚至在非常简单的情况下,一个新的精确算法描述,是经验上快速的有界树宽和有界数量的状态每个变量的网络。在这种假设下,相同的算法被用作MAP的全多项式时间近似方案的基础。近似方案通常被认为是不可能的这个问题,但我们显示,否则类的网络,在实践中是重要的。使用一些著名的网络以及随机生成的情况下,广泛测试的算法,以显示其有效性。

英文摘要:

This paper presents new results for the (partial) maximum a posteriori (MAP) problem in Bayesian networks, which is the problem of querying the most probable state configuration of some of the network variables given evidence. First, it is demonstrated that the problem remains hard even in networks with very simple topology, such as binary polytrees and simple trees (including the Naive Bayes structure). Such proofs extend previous complexity results for the problem. Inapproximability results are also derived in the case of trees if the number of states per variable is not bounded. Although the problem is shown to be hard and inapproximable even in very simple scenarios, a new exact algorithm is described that is empirically fast in networks of bounded treewidth and bounded number of states per variable. The same algorithm is used as basis of a Fully Polynomial Time Approximation Scheme for MAP under such assumptions. Approximation schemes were generally thought to be impossible for this problem, but we show otherwise for classes of networks that are important in practice. The algorithms are extensively tested using some well-known networks as well as random generated cases to show their effectiveness.

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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