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Séminaire Images Optimisation et Probabilités

Hyper-Parameter Selection by Algorithmic Differentiation

Samuel Vaiter

( Institut de Mathématiques de Bourgogne )

Salle de Conférences

le 25 février 2021 à 11:00

Setting regularization parameters for variational estimators in imaging or machine learning is notoriously difficult. Grid-search requires to choose a predefined grid of parameters and scales exponentially in the number of parameters which can be quickly inconvenient or even impossible in imaging. Another class of approaches casts hyperparameter optimization as a bi-level optimization problem, typically solved by gradient descent. The key challenge for these approaches is the estimation of the gradient w.r.t. the hyperparameters. In this presentation, I will show algorithmic/automatic differentiation can help to overcome this challenge, both for inverse problems with a differentiable Stein Unbiased Risk Estimator and in regression using held-out loss.