Publications

2025

1. PREPRINT

   

   Sample complexity of optimal transport barycenters with discrete support

   Léo Portales, Elsa Cazelles, and Edouard Pauwels

   May 2025

   Abs arXiv Bib PDF Code Slides

   Computational implementation of optimal transport barycenters for a set of target probability measures requires a form of approximation, a widespread solution being empirical approximation of measures. We provide an O( p N/n) statistical generalization bounds for the empirical sparse optimal transport barycenters problem, where N is the maximum cardinality of the barycenter (sparse support) and n is the sample size of the target measures empirical approximation. Our analysis includes various optimal transport divergences including Wasserstein, Sinkhorn and Sliced-Wasserstein. We discuss the application of our result to specific settings including K-means, constrained K-means, free and fixed support Wasserstein barycenters.

   @article{portales2025samplecomplexityoptimaltransportbarycentersdiscretesupport,
     title = {Sample complexity of optimal transport barycenters with discrete support},
     author = {Portales, Léo and Cazelles, Elsa and Pauwels, Edouard},
     year = {2025},
     month = may,
     publisher = {Arxiv},
     eprint = {2505.21274},
     archiveprefix = {arXiv},
     primaryclass = {PREPRINT},
   }

2024

1. MOOR

   

   On the sequential convergence of Lloyd’s algorithms

   Léo Portales, Elsa Cazelles, and Edouard Pauwels

   May 2024

   Abs arXiv Bib PDF Code Slides

   Lloyd’s algorithm is an iterative method that solves the quantization problem, i.e. the approximation of a target probability measure by a discrete one, and is particularly used in digital applications.This algorithm can be interpreted as a gradient method on a certain quantization functional which is given by optimal transport. We study the sequential convergence (to a single accumulation point) for two variants of Lloyd’s method: (i) optimal quantization with an arbitrary discrete measure and (ii) uniform quantization with a uniform discrete measure. For both cases, we prove sequential convergence of the iterates under an analiticity assumption on the density of the target measure. This includes for example analytic densities truncated to a compact semi-algebraic set. The argument leverages the log analytic nature of globally subanalytic integrals, the interpretation of Lloyd’s method as a gradient method and the convergence analysis of gradient algorithms under Kurdyka-Lojasiewicz assumptions. As a by-product, we also obtain definability results for more general semi-discrete optimal transport losses such as transport distances with general costs, the max-sliced Wasserstein distance and the entropy regularized optimal transport loss.

   @article{portales2024sequentialconvergencelloydsalgorithms,
     title = {On the sequential convergence of Lloyd's algorithms},
     author = {Portales, Léo and Cazelles, Elsa and Pauwels, Edouard},
     year = {2024},
     month = may,
     publisher = {Arxiv},
     eprint = {2405.20744},
     archiveprefix = {arXiv},
     primaryclass = {MOOR},
   }