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Variational regularization is commonly used to solve linear inverse problems, and involves augmenting a data fidelity by a regularizer. The regularizer is used to promote a priori information and is weighted by a regularization parameter.…

Optimization and Control · Mathematics 2024-01-23 Matthias J. Ehrhardt , Silvia Gazzola , Sebastian J. Scott

We consider the problem of designing efficient regularization algorithms when regularization is encoded by a (strongly) convex functional. Unlike classical penalization methods based on a relaxation approach, we propose an iterative method…

Optimization and Control · Mathematics 2017-07-19 Simon Matet , Lorenzo Rosasco , Silvia Villa , Bang Long Vu

Given a convex optimization problem and its dual, there are many possible first-order algorithms. In this paper, we show the equivalence between mirror descent algorithms and algorithms generalizing the conditional gradient method. This is…

Machine Learning · Computer Science 2013-10-21 Francis Bach

We study variational regularisation methods for inverse problems with imperfect forward operators whose errors can be modelled by order intervals in a partial order of a Banach lattice. We carry out analysis with respect to existence and…

Numerical Analysis · Mathematics 2020-12-25 Leon Bungert , Martin Burger , Yury Korolev , Carola-Bibiane Schoenlieb

We consider a regularization concept for the solution of ill--posed operator equations, where the operator is composed of a continuous and a discontinuous operator. A particular application is level set regularization, where we develop a…

Numerical Analysis · Mathematics 2020-11-16 F. Frühauf , O. Scherzer , A. Leitao

Inverse Problems in medical imaging and computer vision are traditionally solved using purely model-based methods. Among those variational regularization models are one of the most popular approaches. We propose a new framework for applying…

Computer Vision and Pattern Recognition · Computer Science 2019-01-14 Sebastian Lunz , Ozan Öktem , Carola-Bibiane Schönlieb

In this chapter we provide a theoretically founded investigation of state-of-the-art learning approaches for inverse problems from the point of view of spectral reconstruction operators. We give an extended definition of regularization…

Numerical Analysis · Mathematics 2024-06-05 Martin Burger , Samira Kabri

In this work, we investigate various approaches that use learning from training data to solve inverse problems, following a bi-level learning approach. We consider a general framework for optimal inversion design, where training data can be…

Numerical Analysis · Mathematics 2021-10-07 Julianne Chung , Matthias Chung , Silvia Gazzola , Mirjeta Pasha

We propose and analyze a variant of the classic Polyak-Ruppert averaging scheme, broadly used in stochastic gradient methods. Rather than a uniform average of the iterates, we consider a weighted average, with weights decaying in a…

Machine Learning · Computer Science 2018-02-23 Gergely Neu , Lorenzo Rosasco

Recent progress concerning regularization of supersymmetric theories is reviewed. Dimensional reduction is reformulated in a mathematically consistent way, and an elegant and general method is presented that allows to study the…

High Energy Physics - Phenomenology · Physics 2007-05-23 Dominik Stöckinger

In this paper we investigate a variety of deep learning strategies for solving inverse problems. We classify existing deep learning solutions for inverse problems into three categories of Direct Mapping, Data Consistency Optimizer, and Deep…

Computer Vision and Pattern Recognition · Computer Science 2021-11-16 Shima Kamyab , Zohreh Azimifar , Rasool Sabzi , Paul Fieguth

We analyze a new approach to Machine Learning coming from a modification of classical regularization networks by casting the process in the time dimension, leading to a sort of collapse of dimensionality in the problem of learning the model…

Machine Learning · Computer Science 2017-01-05 Marco Gori , Marco Maggini , Alessandro Rossi

We consider efficient methods for computing solutions to dynamic inverse problems, where both the quantities of interest and the forward operator (measurement process) may change at different time instances but we want to solve for all the…

Numerical Analysis · Mathematics 2021-07-14 Mirjeta Pasha , Arvind K. Saibaba , Silvia Gazzola , Malena I. Espanol , Eric de Sturler

Regularisation allows one to handle ill-posed inverse problems. Here we focus on discrete unfolding problems. The properties of the results are characterised by the consistency between measurements and unfolding result and by the posterior…

Data Analysis, Statistics and Probability · Physics 2023-09-07 Michael Schmelling

In this paper, we introduce a novel two-point gradient method for solving the ill-posed problems in Banach spaces and study its convergence analysis. The method is based on the well known iteratively regularized Landweber iteration method…

Numerical Analysis · Mathematics 2022-05-12 Gaurav Mittal , Ankik Kumar Giri

Recent years have seen a flurry of activities in designing provably efficient nonconvex procedures for solving statistical estimation problems. Due to the highly nonconvex nature of the empirical loss, state-of-the-art procedures often…

Machine Learning · Computer Science 2020-06-09 Cong Ma , Kaizheng Wang , Yuejie Chi , Yuxin Chen

Many challenging image processing tasks can be described by an ill-posed linear inverse problem: deblurring, deconvolution, inpainting, compressed sensing, and superresolution all lie in this framework. Traditional inverse problem solvers…

Computer Vision and Pattern Recognition · Computer Science 2019-06-05 Davis Gilton , Greg Ongie , Rebecca Willett

In this paper we explore the role of duality principles within the problem of rotation averaging, a fundamental task in a wide range of computer vision applications. In its conventional form, rotation averaging is stated as a minimization…

Computer Vision and Pattern Recognition · Computer Science 2017-11-30 Anders Eriksson , Carl Olsson , Fredrik Kahl , Tat-Jun Chin

We introduce a novel family of invariant, convex, and non-quadratic functionals that we employ to derive regularized solutions of ill-posed linear inverse imaging problems. The proposed regularizers involve the Schatten norms of the Hessian…

Optimization and Control · Mathematics 2014-02-20 Stamatios Lefkimmiatis , John Paul Ward , Michael Unser

In this paper we provide a detailed analysis of the iteration complexity of dual first order methods for solving conic convex problems. When it is difficult to project on the primal feasible set described by convex constraints, we use the…

Optimization and Control · Mathematics 2015-03-16 Ion Necoara , Andrei Patrascu