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Counting and Sampling Subsets Using Block Covers
Proceedings of the 42nd Conference on Uncertainty in Artificial Intelligence, PMLR 337:3477-3486, 2026.
Abstract
We present a new data structure, *block cover*, for approximate weighted counting and sampling of subsets of a given query set. Such queries are the main computational bottleneck, e.g., in advanced {Markov} chain Monte Carlo algorithms for {Bayesian} learning of {Bayesian} networks. Given a collection of weighted subsets of a ground set $N$, our key idea is to select a few moderate-size subsets $B$ of $N$, called blocks, so as to cover all or most of the input collection by the power sets $2^B$. An approximate sum over the subsets of a query set $Q$ is obtained by adding up the contributions within each block, which contibutions we precompute. We also give a similar, efficient algorithm for generating a subset of $Q$ with probability proportional to its weight. Our empirical results suggest that block covers are superior to previous approaches, which consider the subsets of interest one by one.