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In this paper, we consider the minimization of a Tikhonov functional with an $\ell_1$ penalty for solving linear inverse problems with sparsity constraints. One of the many approaches used to solve this problem uses the Nemskii operator to…

Numerical Analysis · Mathematics 2020-08-26 Fabian Hinterer , Simon Hubmer , Ronny Ramlau

This paper studies the shallow Ritz method for solving the one-dimensional diffusion problem. It is shown that the shallow Ritz method improves the order of approximation dramatically for non-smooth problems. To realize this optimal or…

Numerical Analysis · Mathematics 2025-11-25 Zhiqiang Cai , Anastassia Doktorova , Robert D. Falgout , César Herrera

In this paper, we propose different algorithms for the solution of a tensor linear discrete ill-posed problem arising in the application of the meshless method for solving PDEs in three-dimensional space using multiquadric radial basis…

Numerical Analysis · Mathematics 2021-03-04 M. El Guide , K. Jbilou , A. Ratnani

In many applications of deep learning, particularly those in image restoration, it is either very difficult, prohibitively expensive, or outright impossible to obtain paired training data precisely as in the real world. In such cases, one…

Computer Vision and Pattern Recognition · Computer Science 2018-11-20 Bolin Liu , Xiao Shu , Xiaolin Wu

We analyze Newton's method with lazy Hessian updates for solving general possibly non-convex optimization problems. We propose to reuse a previously seen Hessian for several iterations while computing new gradients at each step of the…

Optimization and Control · Mathematics 2023-06-16 Nikita Doikov , El Mahdi Chayti , Martin Jaggi

Square-root (loss) regularized models have recently become popular in linear regression due to their nice statistical properties. Moreover, some of these models can be interpreted as the distributionally robust optimization counterparts of…

Optimization and Control · Mathematics 2023-10-06 Hong T. M. Chu , Kim-Chuan Toh , Yangjing Zhang

Deep neural networks have demonstrated highly competitive performance in super-resolution (SR) for natural images by learning mappings from low-resolution (LR) to high-resolution (HR) images. However, hyperspectral super-resolution remains…

Image and Video Processing · Electrical Eng. & Systems 2025-05-02 Usman Muhammad , Jorma Laaksonen , Lyudmila Mihaylova

We study the composite convex optimization problems with a Quasi-Self-Concordant smooth component. This problem class naturally interpolates between classic Self-Concordant functions and functions with Lipschitz continuous Hessian.…

Optimization and Control · Mathematics 2023-08-29 Nikita Doikov

The pseudo-likelihood method is one of the most popular algorithms for learning sparse binary pairwise Markov networks. In this paper, we formulate the $L_1$ regularized pseudo-likelihood problem as a sparse multiple logistic regression…

Machine Learning · Statistics 2017-04-10 Sinong Geng , Zhaobin Kuang , David Page

The doubly nonnegative (DNN) cone, being the set of all positive semidefinite matrices whose elements are nonnegative, is a popular approximation of the computationally intractable completely positive cone. The major difficulty for…

Optimization and Control · Mathematics 2021-09-02 Ying Cui , Ling Liang , Defeng Sun , Kim-Chuan Toh

State-of-the-art image reconstruction often relies on complex, highly parameterized deep architectures. We propose an alternative: a data-driven reconstruction method inspired by the classic Tikhonov regularization. Our approach iteratively…

Image and Video Processing · Electrical Eng. & Systems 2025-02-07 Mehrsa Pourya , Erich Kobler , Michael Unser , Sebastian Neumayer

In mathematical optimization, second-order Newton's methods generally converge faster than first-order methods, but they require the inverse of the Hessian, hence are computationally expensive. However, we discover that on sparse graphs,…

Machine Learning · Computer Science 2022-05-30 Nima Dehmamy , Csaba Both , Jianzhi Long , Rose Yu

This paper is concerned with the solution of large-scale linear discrete ill-posed problems with error-contaminated data. Tikhonov regularization is a popular approach to determine meaningful approximate solutions of such problems. The…

Numerical Analysis · Mathematics 2016-02-11 Guangxin Huang , Silvia Noschese , Lothar Reichel

Sparse recovery is ubiquitous in machine learning and signal processing. Due to the NP-hard nature of sparse recovery, existing methods are known to suffer either from restrictive (or even unknown) applicability conditions, or high…

Signal Processing · Electrical Eng. & Systems 2024-03-21 William de Vazelhes , Bhaskar Mukhoty , Xiao-Tong Yuan , Bin Gu

In the paper, a variant of the \ssstar Newton method is developed for the numerical solution of generalized equations, in which the multi-valued part is a so-called SCD (subspace containing derivative) mapping. Under a rather mild…

Numerical Analysis · Mathematics 2022-10-13 H. Gfrerer , M. Mandlmayr , J. V. Outrata , J. Valdman

Depth maps captured with commodity sensors often require super-resolution to be used in applications. In this work we study a super-resolution approach based on a variational problem statement with Tikhonov regularization where the…

Computer Vision and Pattern Recognition · Computer Science 2021-12-22 Milena Gazdieva , Oleg Voynov , Alexey Artemov , Youyi Zheng , Luiz Velho , Evgeny Burnaev

In this paper, the concept of matrix splitting is introduced to solve a large sparse ill-posed linear system via Tikhonov's regularization. In the regularization process, we convert the ill-posed system to a well-posed system. The…

Numerical Analysis · Mathematics 2020-04-15 Ashish Kumar Nandi , Jajati Keshari Sahoo

We propose a non-stationary iterated network Tikhonov (iNETT) method for the solution of ill-posed inverse problems. The iNETT employs deep neural networks to build a data-driven regularizer, and it avoids the difficult task of estimating…

Numerical Analysis · Mathematics 2023-04-05 Davide Bianchi , Guanghao Lai , Wenbin Li

Dynamic Sparse Training (DST) methods train neural networks by maintaining sparsity while dynamically adapting the network topology. Despite the promise of reduced computation, DST methods converge significantly slower than dense training,…

Machine Learning · Computer Science 2026-05-28 Mohammed Adnan , Rohan Jain , Tom Jacobs , Ekansh Sharma , Rahul G. Krishnan , Rebekka Burkholz , Yani Ioannou

The problem of minimizing a sum of local convex objective functions over a networked system captures many important applications and has received much attention in the distributed optimization field. Most of existing work focuses on…

Optimization and Control · Mathematics 2019-01-09 Fatemeh Mansoori , Ermin Wei