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تسجيل مستخدم جديدNorm-Product Belief Propagation: Primal-Dual Message-Passing for Approximate Inference
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In this paper we treat both forms of probabilistic inference, estimating marginal probabilities of the joint distribution and finding the most probable assignment, through a unified message-passing algorithm architecture. We generalize the Belief Propagation (BP) algorithms of sum-product and max-product and tree-rewaighted (TRW) sum and max product algorithms (TRBP) and introduce a new set of convergent algorithms based on convex-free-energy and Linear-Programming (LP) relaxation as a zero-temprature of a convex-free-energy. The main idea of this work arises from taking a general perspective on the existing BP and TRBP algorithms while observing that they all are reductions from the basic optimization formula of $f + sum_i h_i$ where the function $f$ is an extended-valued, strictly convex but non-smooth and the functions $h_i$ are extended-valued functions (not necessarily convex). We use tools from convex duality to present the primal-dual ascent algorithm which is an extension of the Bregman successive projection scheme and is designed to handle optimization of the general type $f + sum_i h_i$. Mapping the fractional-free-energy variational principle to this framework introduces the norm-product message-passing. Special cases include sum-product and max-product (BP algorithms) and the TRBP algorithms. When the fractional-free-energy is set to be convex (convex-free-energy) the norm-product is globally convergent for estimating of marginal probabilities and for approximating the LP-relaxation. We also introduce another branch of the norm-product, the convex-max-product. The convex-max-product is convergent (unlike max-product) and aims at solving the LP-relaxation.
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