Additive averaging kernels speed up finite Markov chains via partition optimization

michaelchchoi · x · 2026-09-22

Paper 4 of the JJSD Monte Carlo special issue thread (open access): Lim & Choi study additive mixtures of Markov kernels Aα = αP + (1−α)G, where P is a baseline sampler and G a Gibbs kernel induced by a partition of the state space — interpretable as a projection of a lifted Markov chain. For the Frobenius objective they derive explicit trace formulae and a Cheeger-type functional characterizing optimal two-block partitions, yielding a submodular optimization problem solvable via majorisation–minimisation, plus geometric decay rates governed by the absolute spectral gap of P. For KL divergence they show convexity-based bounds reduce partition selection to the Gibbs component. Curie–Weiss experiments show suitable partition and α choices significantly accelerate convergence.

Related event: Special Issue Papers: Randomized Step Sizes and Additive Averaging Kernels for MCMC(2 posts)→

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