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Iterative Decomposition Guided Variable Neighborhood Search for Graphical Model Energy Minimization
Proceedings of the 33rd Conference on Uncertainty in Artificial Intelligence, PMLR R15:481-490, 2017.
Abstract
Graphical models factorize a global probabil- ity distribution/energy function as the prod- uct/sum of local functions. A major infer- ence task, known as MAP in Markov Ran- dom Fields and MPE in Bayesian Networks, is to find a global assignment of all the vari- ables with maximum a posteriori probabil- ity/minimum energy. A usual distinction on MAP solving methods is complete/incomplete, i.e. the ability to prove optimality or not. Most complete methods rely on tree search, while incomplete methods rely on local search. Among them, we study Variable Neighbor- hood Search (VNS) for graphical models. In this paper, we propose an iterative approach above VNS which uses (partial) tree search in- side its local neighborhood exploration. The resulting hybrid method offers a good compro- mise between completeness and anytime be- havior than existing tree search methods while still being competitive for proving optimality. We further propose a parallel version of our method improving its anytime behavior on dif- ficult instances coming from a large graphical model benchmark. Last we experiment on the challenging minimum energy problem found in Computational Protein Design, showing the practical benefit of our parallel version. Solver at www.inra.fr/mia/T/toulbar2 v1.0.