arXiv Machine Learning

On two proofs of $d^2$ mixing of weighted Dikin walks

The paper investigates the mixing time of weighted Dikin walks used for sampling from exponential distributions on polytopes and truncated positive-semidefinite cones. It presents a general total-variation mixing bound under conditions of strong self-concordance, ν-symmetry, and mixed-trace regularity, achieving an “~O(d^2)" bound for polytopes and “~O(d^4)" for truncated PSD cones. A second result introduces a fourth-order bootstrap condition that yields stronger χ^2-divergence guarantees and an improved “~O(d^2)" mixing bound for a scaled Lee–Sidford metric.

arXiv Machine Learning
Sep 24

Local Geometric Mixing via Dobrushin Contraction with Applications to Diffusion Path Monte Carlo and the Proximal Sampler

The paper introduces the concept of local geometric mixing, which focuses on geometric convergence to equilibrium in total variation over a finite number of transitions, thereby capturing rapid local equilibration even when global mixing is slow. It derives local geometric mixing bounds using Dobrushin contraction and applies these results to Diffusion Path Monte Carlo, a Markov chain Monte Carlo method that aligns with the Proximal Sampler. The analysis provides mixing guarantees for both the ideal method and its Metropolis-adjusted implementation, and extends recent spectral gap estimates into mixing time bounds.

By Stefan Oberd\"orster
arXiv Machine Learning
Jun 25

Structured Approximations of Measures

arXiv:2310. 09149v3 Announce Type: replace-cross Abstract: We study the approximation of probability measures in the Wasserstein-$p$ distance by structured classes of approximators, motivated by applications in imaging, machine learning, and physical measurement under sensor constraints.

By Keaton Hamm, Varun Khurana
arXiv Machine Learning
Sep 14

Poisson-Corrector Complexity Bounds for Moreau--Yosida Unadjusted Langevin Sampling

arXiv:2609. 12594v1 Announce Type: new Abstract: We study the classical Moreau--Yosida unadjusted Langevin algorithm (MYULA) for $\pi(\,\mathrm{d} x)\propto e^{-f(x)-g(x)}\,\mathrm{d} x$, where $f\in C^2(\mathbb{R}^d)$ is $m$-strongly convex with $L_f$-Lipschitz gradient and $g:\mathbb{R}^d\to\mathbb{R}$ is convex and globally $G$-Lipschitz.

By Yuchen Xin, Zhihua Zhang