Search Results for author: Samuel Vaiter

Found 23 papers, 9 papers with code

Dual Extrapolation for Sparse Generalized Linear Models

1 code implementation12 Jul 2019 Mathurin Massias, Samuel Vaiter, Alexandre Gramfort, Joseph Salmon

Generalized Linear Models (GLM) form a wide class of regression and classification models, where prediction is a function of a linear combination of the input variables.

A framework for bilevel optimization that enables stochastic and global variance reduction algorithms

1 code implementation31 Jan 2022 Mathieu Dagréou, Pierre Ablin, Samuel Vaiter, Thomas Moreau

However, computing the gradient of the value function involves solving a linear system, which makes it difficult to derive unbiased stochastic estimates.

Bilevel Optimization

Convergence and Stability of Graph Convolutional Networks on Large Random Graphs

1 code implementation NeurIPS 2020 Nicolas Keriven, Alberto Bietti, Samuel Vaiter

We study properties of Graph Convolutional Networks (GCNs) by analyzing their behavior on standard models of random graphs, where nodes are represented by random latent variables and edges are drawn according to a similarity kernel.

valid

On the Universality of Graph Neural Networks on Large Random Graphs

1 code implementation NeurIPS 2021 Nicolas Keriven, Alberto Bietti, Samuel Vaiter

In the large graph limit, GNNs are known to converge to certain "continuous" models known as c-GNNs, which directly enables a study of their approximation power on random graph models.

Stochastic Block Model

Linear Support Vector Regression with Linear Constraints

1 code implementation6 Nov 2019 Quentin Klopfenstein, Samuel Vaiter

This paper studies the addition of linear constraints to the Support Vector Regression (SVR) when the kernel is linear.

regression

Characterizing the maximum parameter of the total-variation denoising through the pseudo-inverse of the divergence

no code implementations8 Dec 2016 Charles-Alban Deledalle, Nicolas Papadakis, Joseph Salmon, Samuel Vaiter

Though, it is of importance when tuning the regularization parameter as it allows fixing an upper-bound on the grid for which the optimal parameter is sought.

Denoising

Low Complexity Regularization of Linear Inverse Problems

no code implementations7 Jul 2014 Samuel Vaiter, Gabriel Peyré, Jalal M. Fadili

Inverse problems and regularization theory is a central theme in contemporary signal processing, where the goal is to reconstruct an unknown signal from partial indirect, and possibly noisy, measurements of it.

Model Consistency of Partly Smooth Regularizers

no code implementations5 May 2014 Samuel Vaiter, Gabriel Peyré, Jalal M. Fadili

We show that a generalized "irrepresentable condition" implies stable model selection under small noise perturbations in the observations and the design matrix, when the regularization parameter is tuned proportionally to the noise level.

Model Selection

Sparse and Smooth: improved guarantees for Spectral Clustering in the Dynamic Stochastic Block Model

no code implementations7 Feb 2020 Nicolas Keriven, Samuel Vaiter

Existing results show that, in the relatively sparse case where the expected degree grows logarithmically with the number of nodes, guarantees in the static case can be extended to the dynamic case and yield improved error bounds when the DSBM is sufficiently smooth in time, that is, the communities do not change too much between two time steps.

Clustering Stochastic Block Model

Automated data-driven selection of the hyperparameters for Total-Variation based texture segmentation

no code implementations20 Apr 2020 Barbara Pascal, Samuel Vaiter, Nelly Pustelnik, Patrice Abry

This work extends the Stein's Unbiased GrAdient estimator of the Risk of Deledalle et al. to the case of correlated Gaussian noise, deriving a general automatic tuning of regularization parameters.

Model identification and local linear convergence of coordinate descent

no code implementations22 Oct 2020 Quentin Klopfenstein, Quentin Bertrand, Alexandre Gramfort, Joseph Salmon, Samuel Vaiter

For composite nonsmooth optimization problems, Forward-Backward algorithm achieves model identification (e. g. support identification for the Lasso) after a finite number of iterations, provided the objective function is regular enough.

Block based refitting in $\ell_{12}$ sparse regularisation

no code implementations22 Oct 2019 Charles-Alban Deledalle, Nicolas Papadakis, Joseph Salmon, Samuel Vaiter

This is done through the use of refitting block penalties that only act on the support of the estimated solution.

Image Restoration

A theory of optimal convex regularization for low-dimensional recovery

no code implementations7 Dec 2021 Yann Traonmilin, Rémi Gribonval, Samuel Vaiter

To perform recovery, we consider the minimization of a convex regularizer subject to a data fit constraint.

Supervised learning of analysis-sparsity priors with automatic differentiation

no code implementations15 Dec 2021 Hashem Ghanem, Joseph Salmon, Nicolas Keriven, Samuel Vaiter

In most situations, this dictionary is not known, and is to be recovered from pairs of ground-truth signals and measurements, by minimizing the reconstruction error.

Denoising Image Reconstruction

Automatic differentiation of nonsmooth iterative algorithms

no code implementations31 May 2022 Jérôme Bolte, Edouard Pauwels, Samuel Vaiter

Is there a limiting object for nonsmooth piggyback automatic differentiation (AD)?

The derivatives of Sinkhorn-Knopp converge

no code implementations26 Jul 2022 Edouard Pauwels, Samuel Vaiter

We show that the derivatives of the Sinkhorn-Knopp algorithm, or iterative proportional fitting procedure, converge towards the derivatives of the entropic regularization of the optimal transport problem with a locally uniform linear convergence rate.

A Lower Bound and a Near-Optimal Algorithm for Bilevel Empirical Risk Minimization

no code implementations17 Feb 2023 Mathieu Dagréou, Thomas Moreau, Samuel Vaiter, Pierre Ablin

Bilevel optimization problems, which are problems where two optimization problems are nested, have more and more applications in machine learning.

Bilevel Optimization

On the Robustness of Text Vectorizers

no code implementations9 Mar 2023 Rémi Catellier, Samuel Vaiter, Damien Garreau

A fundamental issue in machine learning is the robustness of the model with respect to changes in the input.

Sentence

Gradient scarcity with Bilevel Optimization for Graph Learning

1 code implementation24 Mar 2023 Hashem Ghanem, Samuel Vaiter, Nicolas Keriven

To alleviate this issue, we study several solutions: we propose to resort to latent graph learning using a Graph-to-Graph model (G2G), graph regularization to impose a prior structure on the graph, or optimizing on a larger graph than the original one with a reduced diameter.

Bilevel Optimization Graph Learning

Convergence of Message Passing Graph Neural Networks with Generic Aggregation On Large Random Graphs

no code implementations21 Apr 2023 Matthieu Cordonnier, Nicolas Keriven, Nicolas Tremblay, Samuel Vaiter

We study the convergence of message passing graph neural networks on random graph models to their continuous counterpart as the number of nodes tends to infinity.

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