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Learning to sample fibers for goodness-of-fit testing

Ivan Gvozdanović and Sonja Petrović

Vol. 17 (2026), No. 1, 33–73
Abstract

We consider the problem of constructing exact goodness-of-fit tests for discrete exponential family models. This classical problem remains practically unsolved for many types of structured or sparse data, as it rests on a computationally difficult core task: to produce a reliable sample from lattice points in a high-dimensional polytope. We translate the problem into a Markov decision process and demonstrate a reinforcement learning approach for learning “good moves” for sampling. We illustrate the approach on data sets and models for which traditional MCMC samplers converge too slowly due to problem size, sparsity structure, and the requirement to use prohibitive nonlinear algebra computations in the process. The differentiating factor is the use of scalable tools from linear algebra in the context of theoretical guarantees provided by nonlinear algebra. Our algorithm is based on an actor-critic sampling scheme, with provable convergence. The discovered moves can be used to efficiently obtain an exchangeable sample, significantly cutting computational times with regards to statistical testing.

Keywords
Markov chain Monte Carlo, fiber sampling, Markov basis, exact conditional test, actor-critic algorithms, reinforcement learning
Mathematical Subject Classification
Primary: 62R01
Secondary: 68W20
Milestones
Received: 15 April 2025
Revised: 29 August 2025
Accepted: 13 October 2025
Published: 29 December 2025
Authors
Ivan Gvozdanović
Department of Applied Mathematics
Illinois Institute of Technology
Chicago, IL
United States
Sonja Petrović
Department of Applied Mathematics
Illinois Institute of Technology
Chicago, IL
United States