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We consider regularization methods based on the coupling of Tikhonov regularization and projection strategies. From the resulting constraint regularization method we obtain level set methods in a straight forward way. Moreover, we show that…

Optimization and Control · Mathematics 2020-11-17 A. Leitao , O. Scherzer

We investigate the problem of certifying optimality for sparse generalized linear models (GLMs), where sparsity is enforced through a cardinality constraint. While Branch-and-Bound (BnB) frameworks can certify optimality using perspective…

Optimization and Control · Mathematics 2026-03-03 Jiachang Liu , Andrea Lodi , Soroosh Shafiee

We present an active-set method for minimizing an objective that is the sum of a convex quadratic and $\ell_1$ regularization term. Unlike two-phase methods that combine a first-order active set identification step and a subspace phase…

Optimization and Control · Mathematics 2014-12-08 Stefan Solntsev , Jorge Nocedal , Richard Byrd

In many scenarios, one uses a large training set to train a model with the goal of performing well on a smaller testing set with a different distribution. Learning a weight for each data point of the training set is an appealing solution,…

Machine Learning · Statistics 2023-10-27 Anastasia Ivanova , Pierre Ablin

In this paper we present a new regularization term for variational image restoration which can be regarded as a space-variant anisotropic extension of the classical isotropic Total Variation (TV) regularizer. The proposed regularizer comes…

Image and Video Processing · Electrical Eng. & Systems 2019-08-05 Luca Calatroni , Alessandro Lanza , Monica Pragliola , Fiorella Sgallari

We propose a novel 3d shape representation for 3d shape reconstruction from a single image. Rather than predicting a shape directly, we train a network to generate a training set which will be fed into another learning algorithm to define…

Computer Vision and Pattern Recognition · Computer Science 2022-05-02 Biao Zhang , Peter Wonka

We design and analyze a novel accelerated gradient-based algorithm for a class of bilevel optimization problems. These problems have various applications arising from machine learning and image processing, where optimal solutions of the two…

Optimization and Control · Mathematics 2023-11-20 Sepideh Samadi , Daniel Burbano , Farzad Yousefian

A trained-based Born iterative method (TBIM) is developed for electromagnetic imaging (EMI) applications. The proposed TBIM consists of a nested loop; the outer loop executes TBIM iteration steps, while the inner loop executes a trained…

Image and Video Processing · Electrical Eng. & Systems 2022-11-23 Abdulla Desmal

We explore the use of the recently proposed "total nuclear variation" (TNV) as a regularizer for reconstructing multi-channel, spectral CT images. This convex penalty is a natural extension of the total variation (TV) to vector-valued…

Medical Physics · Physics 2015-06-23 David Rigie , Patrick La Riviere

L2-TGV-regularization has been introduced by Bredies, Kunisch, and Pock. This regularization method requires careful tuning of two regularization parameters. The focus of this paper is to derive analytical results, which allow for…

Functional Analysis · Mathematics 2013-09-30 Christiane Pöschl , Otmar Scherzer

Enhancing images in low-light scenes is a challenging but widely concerned task in the computer vision. The mainstream learning-based methods mainly acquire the enhanced model by learning the data distribution from the specific scenes,…

Computer Vision and Pattern Recognition · Computer Science 2023-06-05 Long Ma , Dian Jin , Nan An , Jinyuan Liu , Xin Fan , Risheng Liu

Image reconstruction in X-ray tomography is an ill-posed inverse problem, particularly with limited available data. Regularization is thus essential, but its effectiveness hinges on the choice of a regularization parameter that balances…

Computer Vision and Pattern Recognition · Computer Science 2026-02-11 Chuyang Wu , Samuli Siltanen

Stochastic optimization plays a crucial role in the advancement of deep learning technologies. Over the decades, significant effort has been dedicated to improving the training efficiency and robustness of deep neural networks, via various…

Machine Learning · Computer Science 2024-08-21 Huixiu Jiang , Ling Yang , Yu Bao , Rutong Si , Sikun Yang

Diverse inverse problems in imaging can be cast as variational problems composed of a task-specific data fidelity term and a regularization term. In this paper, we propose a novel learnable general-purpose regularizer exploiting recent…

Optimization and Control · Mathematics 2020-02-19 Erich Kobler , Alexander Effland , Karl Kunisch , Thomas Pock

Learning neural networks using only few available information is an important ongoing research topic with tremendous potential for applications. In this paper, we introduce a powerful regularizer for the variational modeling of inverse…

Machine Learning · Computer Science 2023-05-17 Fabian Altekrüger , Alexander Denker , Paul Hagemann , Johannes Hertrich , Peter Maass , Gabriele Steidl

We consider a bilevel learning framework for learning linear operators. In this framework, the learnable parameters are optimized via a loss function that also depends on the minimizer of a convex optimization problem (denoted lower-level…

Optimization and Control · Mathematics 2025-06-10 Lea Bogensperger , Matthias J. Ehrhardt , Thomas Pock , Mohammad Sadegh Salehi , Hok Shing Wong

In this paper we explore the potential of the double phase functional in an image processing context. To this end, we study minimizers of the double phase energy for functions with bounded variation and show that this energy can be obtained…

Analysis of PDEs · Mathematics 2021-05-27 Petteri Harjulehto , Peter Hästö

We propose a bilevel optimization approach for the estimation of parameters in nonlocal image denoising models. The parameters we consider are both the fidelity weight and weights within the kernel of the nonlocal operator. In both cases we…

Optimization and Control · Mathematics 2021-09-24 M. D'Elia , J. C. De los Reyes , A. Miniguano-Trujillo

Solving image classification tasks given small training datasets remains an open challenge for modern computer vision. Aggressive data augmentation and generative models are among the most straightforward approaches to overcoming the lack…

Computer Vision and Pattern Recognition · Computer Science 2023-09-06 Lorenzo Brigato , Stavroula Mougiakakou

Dropout and similar stochastic neural network regularization methods are often interpreted as implicitly averaging over a large ensemble of models. We propose STE (stochastically trained ensemble) layers, which enhance the averaging…

Machine Learning · Computer Science 2019-11-22 Alex Labach , Shahrokh Valaee