Search Results for author: Saverio Salzo

Found 18 papers, 5 papers with code

On the Iteration Complexity of Hypergradient Computations

no code implementations ICML 2020 Riccardo Grazzi, Saverio Salzo, Massimiliano Pontil, Luca Franceschi

We study a general class of bilevel optimization problems, in which the upper-level objective is defined via the solution of a fixed point equation.

Bilevel Optimization Computational Efficiency +1

Nonsmooth Implicit Differentiation: Deterministic and Stochastic Convergence Rates

no code implementations18 Mar 2024 Riccardo Grazzi, Massimiliano Pontil, Saverio Salzo

We study the problem of efficiently computing the derivative of the fixed-point of a parametric nondifferentiable contraction map.

Data Poisoning Hyperparameter Optimization +1

Relax and penalize: a new bilevel approach to mixed-binary hyperparameter optimization

no code implementations21 Aug 2023 Marianna de Santis, Jordan Frecon, Francesco Rinaldi, Saverio Salzo, Martin Schmidt

In recent years, bilevel approaches have become very popular to efficiently estimate high-dimensional hyperparameters of machine learning models.

Hyperparameter Optimization

Variance reduction techniques for stochastic proximal point algorithms

no code implementations18 Aug 2023 Cheik Traoré, Vassilis Apidopoulos, Saverio Salzo, Silvia Villa

Stochastic proximal point algorithms have been studied as an alternative to stochastic gradient algorithms since they are more stable with respect to the choice of the stepsize but a proper variance reduced version is missing.

Bilevel Optimization with a Lower-level Contraction: Optimal Sample Complexity without Warm-start

2 code implementations NeurIPS 2023 Riccardo Grazzi, Massimiliano Pontil, Saverio Salzo

We analyse a general class of bilevel problems, in which the upper-level problem consists in the minimization of a smooth objective function and the lower-level problem is to find the fixed point of a smooth contraction map.

Bilevel Optimization Data Poisoning +2

Convergence of Batch Greenkhorn for Regularized Multimarginal Optimal Transport

no code implementations1 Dec 2021 Vladimir Kostic, Saverio Salzo, Massimilano Pontil

In this work we propose a batch version of the Greenkhorn algorithm for multimarginal regularized optimal transport problems.

The method of Bregman projections in deterministic and stochastic convex feasibility problems

no code implementations5 Jan 2021 Vladimir Kostic, Saverio Salzo

We analyze in depth the case of affine feasibility problems showing that the iterates generated by the proposed methods converge Q-linearly and providing also explicit global and local rates of convergence.

Optimization and Control 90C25, 65K05, 49M37, 90C15, 90C06

Convergence Properties of Stochastic Hypergradients

no code implementations13 Nov 2020 Riccardo Grazzi, Massimiliano Pontil, Saverio Salzo

Bilevel optimization problems are receiving increasing attention in machine learning as they provide a natural framework for hyperparameter optimization and meta-learning.

Bilevel Optimization Hyperparameter Optimization +1

On the Iteration Complexity of Hypergradient Computation

1 code implementation29 Jun 2020 Riccardo Grazzi, Luca Franceschi, Massimiliano Pontil, Saverio Salzo

We study a general class of bilevel problems, consisting in the minimization of an upper-level objective which depends on the solution to a parametric fixed-point equation.

Computational Efficiency Hyperparameter Optimization +1

Efficient Tensor Kernel methods for sparse regression

no code implementations23 Mar 2020 Feliks Hibraj, Marcello Pelillo, Saverio Salzo, Massimiliano Pontil

Second, we use a Nystrom-type subsampling approach, which allows for a training phase with a smaller number of data points, so to reduce the computational cost.

regression

Sinkhorn Barycenters with Free Support via Frank-Wolfe Algorithm

1 code implementation NeurIPS 2019 Giulia Luise, Saverio Salzo, Massimiliano Pontil, Carlo Ciliberto

We present a novel algorithm to estimate the barycenter of arbitrary probability distributions with respect to the Sinkhorn divergence.

Bilevel learning of the Group Lasso structure

no code implementations NeurIPS 2018 Jordan Frecon, Saverio Salzo, Massimiliano Pontil

Regression with group-sparsity penalty plays a central role in high-dimensional prediction problems.

Bilevel Optimization

Far-HO: A Bilevel Programming Package for Hyperparameter Optimization and Meta-Learning

2 code implementations13 Jun 2018 Luca Franceschi, Riccardo Grazzi, Massimiliano Pontil, Saverio Salzo, Paolo Frasconi

In (Franceschi et al., 2018) we proposed a unified mathematical framework, grounded on bilevel programming, that encompasses gradient-based hyperparameter optimization and meta-learning.

Hyperparameter Optimization Meta-Learning

Latent Variable Time-varying Network Inference

1 code implementation12 Feb 2018 Federico Tomasi, Veronica Tozzo, Saverio Salzo, Alessandro Verri

The estimation of the contribution of the latent factors is embedded in the model which produces both sparse and low-rank components for each time point.

Sociology Time Series +1

Solving $\ell^p\!$-norm regularization with tensor kernels

no code implementations18 Jul 2017 Saverio Salzo, Johan A. K. Suykens, Lorenzo Rosasco

In this paper, we discuss how a suitable family of tensor kernels can be used to efficiently solve nonparametric extensions of $\ell^p$ regularized learning methods.

Generalized support vector regression: duality and tensor-kernel representation

no code implementations18 Mar 2016 Saverio Salzo, Johan A. K. Suykens

In this paper we study the variational problem associated to support vector regression in Banach function spaces.

regression

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