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Improving Optimization-Based Approximate Inference by Clamping Variables
Proceedings of the 33rd Conference on Uncertainty in Artificial Intelligence, PMLR R15:441-450, 2017.
Abstract
While central to the application of probabilis- tic models to discrete data, the problem of marginal inference is in general intractable and efficient approximation schemes need to exploit the problem structure. Recently, there have been efforts to develop inference techniques that do not necessarily make factorization as- sumptions about the distribution, but rather ex- ploit the fact that sometimes there exist effi- cient algorithms for finding the MAP config- uration. In this paper, we theoretically prove that for discrete multi-label models the bounds on the partition function obtained by two of these approaches, Perturb-and-MAP and the bound from the infinite R{é}nyi divergence, can be only improved by clamping any subset of the variables. For the case of log-supermodular models we provide a more detailed analysis and develop a set of efficient strategies for choos- ing the order in which the variables should be clamped. Finally, we present a number of nu- merical experiments showcasing the improve- ments obtained by the proposed methods on several models.