On finding minimal w-cutset

  • Authors:
  • Bozhena Bidyuk;Rina Dechter

  • Affiliations:
  • University Of California Irvine, Irvine, CA;University Of California Irvine, Irvine, CA

  • Venue:
  • UAI '04 Proceedings of the 20th conference on Uncertainty in artificial intelligence
  • Year:
  • 2004

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Abstract

The complexity of a reasoning task over a graphical model is tied to the induced width of the underlying graph. It is well-known that the conditioning (assigning values) on a subset of variables yields a subproblem of the reduced complexity where instantiated variables are removed. If the assigned variables constitute a cycle-cutset, the rest of the network is singly-connected and therefore can be solved by linear propagation algorithms. A w-cutset is a generalization of a cycle-cutset defined as a subset of nodes such that the subgraph with cutset nodes removed has induced-width of w or less. In this paper we address the problem of finding a minimal w-cutset in a graph. We relate the problem to that of finding the minimal w-cutset of a tree-decomposition. The latter can be mapped to the well-known set multi-cover problem. This relationship yields a proof of NP-completeness on one hand and a greedy algorithm for finding a w-cutset of a tree decomposition on the other. Empirical evaluation of the algorithms is presented.