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Séminaire Images Optimisation et Probabilités

(Proba-stats) Sample and Map from a Single Convex Potential: Generation using Conjugate Moment Measures

Nina Vesseron

( ENSAE )

Salle de conférences

le 10 avril 2025 à 11:15

A common approach to generative modeling is to split model-fitting into two blocks: define first how to sample noise (e.g. Gaussian) and choose next what to do with it (e.g. using a single map or flows). We explore in this work an alternative route that ties sampling and mapping. We find inspiration in moment measures, a result that states that for any measure ρ\rho supported on a compact convex set of Rd\mathbb{R}^d, there exists a unique convex potential uu such that ρ=ueu\rho=\nabla u\,\sharp\,e^{-u}. While this does seem to tie effectively sampling (from log-concave distribution eue^{-u}) and action (pushing particles through u\nabla u), we observe on simple examples (e.g., Gaussians or 1D distributions) that this choice is ill-suited for practical tasks. We study an alternative factorization, where ρ\rho is factorized as wew\nabla w^*\,\sharp\,e^{-w}, where ww^* is the convex conjugate of ww. We call this approach conjugate moment measures, and show far more intuitive results on these examples. Because w\nabla w^* is the Monge map between the log-concave distribution ewe^{-w} and ρ\rho, we rely on optimal transport solvers to propose an algorithm to recover ww from samples of ρ\rho, and parameterize ww as an input convex neural network.