arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2403.08562cs.LGcs.AIcs.DM
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马尔可夫网络基于约束学习的结构视角

Structural perspective on constraint-based learning of Markov networks

University of Bergen(卑尔根大学)

Tuukka Korhonen, Fedor V. Fomin, Pekka Parviainen

AI总结:

本研究从结构视角探讨马尔可夫网络的约束学习,揭示最大成对连通性决定条件集大小,并给出检验数量的上下界,证明有界树宽图可多项式学习。

摘要:

马尔可夫网络是概率图模型,利用无向图来刻画变量之间的条件独立关系。我们的研究聚焦于基于约束的结构学习,即通过执行条件独立性检验从数据中学习无向图。我们针对基于约束的马尔可夫网络学习的两个关键方面建立了理论极限:检验次数和条件集大小。这些界限揭示了图的结构性质与学习马尔可夫网络所需检验数量之间令人兴奋的相互作用。我们工作的出发点是图参数最大成对连通性,即$κ$,也就是图中连接一对顶点的顶点不相交路径的最大数量,它决定了学习该图所需的独立性检验的大小。一方面,我们证明至少一次条件集大小至少为$κ$的检验总是必要的。另一方面,我们证明任何图都可以通过执行大小至多为$κ$的检验来学习。这完全解决了学习该图所需条件集最小大小的问题。在检验数量方面,我们对条件集大小的上界意味着每个具有$n$个顶点的图可以通过至多$n^κ$次条件集大小至多为$κ$的检验来学习。我们证明,对于条件集大小的任何上界$q$,存在具有$O(n q)$个顶点的图,需要至少$n^{Ω(κ)}$次检验才能学习。即使图的树宽和最大度至多为$κ+2$,这个下界也成立。在积极方面,我们证明每个有界树宽的图可以通过多项式次数的检验来学习,其中条件集大小至多为$2κ$。

英文摘要:

Markov networks are probabilistic graphical models that employ undirected graphs to depict conditional independence relationships among variables. Our focus lies in constraint-based structure learning, which entails learning the undirected graph from data through the execution of conditional independence tests. We establish theoretical limits concerning two critical aspects of constraint-based learning of Markov networks: the number of tests and the sizes of the conditioning sets. These bounds uncover an exciting interplay between the structural properties of the graph and the amount of tests required to learn a Markov network. The starting point of our work is that the graph parameter maximum pairwise connectivity, $κ$, that is, the maximum number of vertex-disjoint paths connecting a pair of vertices in the graph, is responsible for the sizes of independence tests required to learn the graph. On one hand, we show that at least one test with the size of the conditioning set at least $κ$ is always necessary. On the other hand, we prove that any graph can be learned by performing tests of size at most $κ$. This completely resolves the question of the minimum size of conditioning sets required to learn the graph. When it comes to the number of tests, our upper bound on the sizes of conditioning sets implies that every $n$-vertex graph can be learned by at most $n^κ$ tests with conditioning sets of sizes at most $κ$. We show that for any upper bound $q$ on the sizes of the conditioning sets, there exist graphs with $O(n q)$ vertices that require at least $n^{Ω(κ)}$ tests to learn. This lower bound holds even when the treewidth and the maximum degree of the graph are at most $κ+2$. On the positive side, we prove that every graph of bounded treewidth can be learned by a polynomial number of tests with conditioning sets of sizes at most $2κ$.

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