
arXiv: 1804.09788
The recently proposed multi-layer sparse model has raised insightful connections between sparse representations and convolutional neural networks (CNN). In its original conception, this model was restricted to a cascade of convolutional synthesis representations. In this paper, we start by addressing a more general model, revealing interesting ties to fully connected networks. We then show that this multi-layer construction admits a brand new interpretation in a unique symbiosis between synthesis and analysis models: while the deepest layer indeed provides a synthesis representation, the mid-layers decompositions provide an analysis counterpart. This new perspective exposes the suboptimality of previously proposed pursuit approaches, as they do not fully leverage all the information comprised in the model constraints. Armed with this understanding, we address fundamental theoretical issues, revisiting previous analysis and expanding it. Motivated by the limitations of previous algorithms, we then propose an integrated - holistic - alternative that estimates all representations in the model simultaneously, and analyze all these different schemes under stochastic noise assumptions. Inspired by the synthesis-analysis duality, we further present a Holistic Pursuit algorithm, which alternates between synthesis and analysis sparse coding steps, eventually solving for the entire model as a whole, with provable improved performance. Finally, we present numerical results that demonstrate the practical advantages of our approach.
Signal Processing (eess.SP), FOS: Computer and information sciences, Iterative numerical methods for linear systems, Computer Science - Machine Learning, Numerical solutions to overdetermined systems, pseudoinverses, Linear operators and ill-posed problems, regularization, sparse coding, Image and Video Processing (eess.IV), Electrical Engineering and Systems Science - Image and Video Processing, neural networks, analysis and synthesis priors, Approximation algorithms, Machine Learning (cs.LG), Neural nets and related approaches to inference from stochastic processes, Computational methods for sparse matrices, Ill-posedness and regularization problems in numerical linear algebra, sparse representations, Image analysis in multivariate analysis, FOS: Electrical engineering, electronic engineering, information engineering, multi-layer representations, Electrical Engineering and Systems Science - Signal Processing
Signal Processing (eess.SP), FOS: Computer and information sciences, Iterative numerical methods for linear systems, Computer Science - Machine Learning, Numerical solutions to overdetermined systems, pseudoinverses, Linear operators and ill-posed problems, regularization, sparse coding, Image and Video Processing (eess.IV), Electrical Engineering and Systems Science - Image and Video Processing, neural networks, analysis and synthesis priors, Approximation algorithms, Machine Learning (cs.LG), Neural nets and related approaches to inference from stochastic processes, Computational methods for sparse matrices, Ill-posedness and regularization problems in numerical linear algebra, sparse representations, Image analysis in multivariate analysis, FOS: Electrical engineering, electronic engineering, information engineering, multi-layer representations, Electrical Engineering and Systems Science - Signal Processing
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