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Block-Value Symmetries in Probabilistic Graphical Models
Proceedings of the 34th Conference on Uncertainty in Artificial Intelligence, PMLR R16:885-894, 2018.
Abstract
One popular way for lifted inference in proba- bilistic graphical models is to first merge sym- metric states into a single cluster (orbit) and then use these for downstream inference, via variations of orbital MCMC [Niepert, 2012]. These orbits are represented compactly us- ing permutations over variables, and variable- value (VV) pairs, but they can miss several state symmetries in a domain. We define the notion of permutations over block-value (BV) pairs, where a block is a set of variables. BV strictly generalizes VV sym- metries, and can compute many more sym- metries for increasing block sizes. To opera- tionalize use of BV permutations in lifted in- ference, we describe 1) an algorithm to com- pute BV permutations given a block parti- tion of the variables, 2) BV-MCMC, an exten- sion of orbital MCMC that can sample from BV orbits, and 3) a heuristic to suggest good block partitions. Our experiments show that BV-MCMC can mix much faster compared to vanilla MCMC and orbital MCMC.