Mad Max: Affine Spline Insights into Deep Learning
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Abstract (arXiv)
We build a rigorous bridge between deep networks (DNs) and approximation theory via spline functions and operators. Our key result is that a large class of DNs can be written as a composition of max-affine spline operators (MASOs), which provide a powerful portal through which to view and analyze their inner workings. For instance, conditioned on the input signal, the output of a MASO DN can be written as a simple affine transformation of the input. This implies that a DN constructs a set of signal-dependent, class-specific templates against which the signal is compared via a simple inner product; we explore the links to the classical theory of optimal classification via matched filters and the effects of data memorization. Going further, we propose a simple penalty term that can be added to the cost function of any DN learning algorithm to force the templates to be orthogonal with each other; this leads to significantly improved classification performance and reduced overfitting with no change to the DN architecture. The spline partition of the input signal space that is implicitly induced by a MASO directly links DNs to the theory of vector quantization (VQ) and K-means clustering, which opens up new geometric avenue to study how DNs organize signals in a hierarchical fashion. To validate the utility of the VQ interpretation, we develop and validate a new distance metric for signals and images that quantifies the difference between their VQ encodings. (This paper is a significantly expanded version of A Spline Theory of Deep Learning from ICML 2018.)
Key facts. Cited by 55 papers in the map (data through 14 Oct 2026). First posted on arXiv 17 May 2018.
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Citing papers per year: 2021: 10; 2022: 15; 2023: 9; 2024: 6; 2025: 7; 2026: 8.
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- 2021CKConv: Continuous Kernel Convolution For Sequential Datacited by 120
- 2021What Kinds of Functions do Deep Neural Networks Learn? Insights from Variational Spline Theorycited by 60
- 2022Mechanistic Mode Connectivitycited by 50
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- 2022On the Number of Regions of Piecewise Linear Neural Networkscited by 21
- 2023Deep Learning Meets Sparse Regularization: A Signal Processing Perspectivecited by 21
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- 2021Ortho-Shot: Low Displacement Rank Regularization with Data Augmentation for Few-Shot Learningcited by 3
- 2024Sparser, Better, Deeper, Stronger: Improving Sparse Training with Exact Orthogonal Initializationcited by 3
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- 2024TTVD: Towards a Geometric Framework for Test-Time Adaptation Based on Voronoi Diagramcited by 2
- 2022Over-parameterization: A Necessary Condition for Models that Extrapolatecited by 1
- 2023Neural Polytopescited by 1
- 2024Mitigating over-exploration in latent space optimization using LEScited by 1
- 2025Computing Linear Regions in Neural Networks with Skip Connectionscited by 1
- 2025Which Way from B to A: The role of embedding geometry in image interpolation for Stable Diffusioncited by 1
- 2025Concept Attractors in LLMs and their Applicationscited by 1
- 2026Characterizing the Discrete Geometry of ReLU Networkscited by 1
- 2021Learning DNN networks using un-rectifying ReLU with compressed sensing applicationcited by 0
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- 2022Towards Global Neural Network Abstractions with Locally-Exact Reconstructioncited by 0
- 2023SpecXAI -- Spectral interpretability of Deep Learning Modelscited by 0
- 2023Unsupervised Discovery of Extreme Weather Events Using Universal Representations of Emergent Organizationcited by 0
- 2023A max-affine spline approximation of neural networks using the Legendre transform of a convex-concave representationcited by 0
- 2024Towards stable training of parallel continual learningcited by 0
- 2024On the Geometry of Deep Learningcited by 0
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50 most cited of 55 All 55 (JSON)
- 2026Hidden Activations are not Enough I: Knowledge Matrices as Higher Representations28 Sep 2026
- 2026Characterizing the Discrete Geometry of ReLU Networks5 Jun 2026
- 2026The Geometric Structure of Models Learning Sparse Data8 May 2026
- 2026Do Sparse Autoencoders Capture Concept Manifolds?30 Apr 2026
- 2026The Linear Centroids Hypothesis: Features as Directions Learned by Local Experts13 Apr 2026
- 2026Divine Benevolence is an x2: GLUs scale asymptotically faster than MLPs16 Feb 2026
- 2026Structural Disentanglement in Bilinear MLPs via Architectural Inductive Bias5 Feb 2026
- 2026Poisson Hyperplane Processes with Rectified Linear Units9 Jan 2026
- 2025Concept Attractors in LLMs and their Applications30 Dec 2025
- 2025Which Way from B to A: The role of embedding geometry in image interpolation for Stable Diffusion16 Nov 2025
- 2025Non-Singularity of the Gradient Descent map for Neural Networks with Piecewise Analytic Activations28 Oct 2025
- 2025Computing Linear Regions in Neural Networks with Skip Connections18 Sep 2025
38 more
- 2025A Priori Generalizability Estimate for a CNN24 Feb 2025
- 2025Free-Knots Kolmogorov-Arnold Network: On the Analysis of Spline Knots and Advancing Stability16 Jan 2025
- 2025Semialgebraic Neural Networks: From roots to representations2 Jan 2025
- 2024TTVD: Towards a Geometric Framework for Test-Time Adaptation Based on Voronoi Diagram10 Dec 2024
- 2024Preventing Dimensional Collapse in Self-Supervised Learning via Orthogonality Regularization1 Nov 2024
- 2024On the Geometry of Deep Learning9 Aug 2024
- 2024Towards stable training of parallel continual learning11 Jul 2024
- 2024Mitigating over-exploration in latent space optimization using LES14 Jun 2024
- 2024Sparser, Better, Deeper, Stronger: Improving Sparse Training with Exact Orthogonal Initialization3 Jun 2024
- 2023Characterizing Large Language Model Geometry Helps Solve Toxicity Detection and Generation4 Dec 2023
- 2023SmoothHess: ReLU Network Feature Interactions via Stein's Lemma1 Nov 2023
- 2023A max-affine spline approximation of neural networks using the Legendre transform of a convex-concave representation16 Jul 2023
- 2023Neural Polytopes3 Jul 2023
- 2023Polyhedral Complex Extraction from ReLU Networks using Edge Subdivision12 Jun 2023
- 2023Deep ReLU Networks Have Surprisingly Simple Polytopes16 May 2023
- 2023Unsupervised Discovery of Extreme Weather Events Using Universal Representations of Emergent Organization25 Apr 2023
- 2023SpecXAI -- Spectral interpretability of Deep Learning Models20 Feb 2023
- 2023Deep Learning Meets Sparse Regularization: A Signal Processing Perspective23 Jan 2023
- 2022Interpreting Neural Networks through the Polytope Lens22 Nov 2022
- 2022Mechanistic Mode Connectivity15 Nov 2022
- 2022Towards Global Neural Network Abstractions with Locally-Exact Reconstruction21 Oct 2022
- 2022What does a deep neural network confidently perceive? The effective dimension of high certainty class manifolds and their low confidence boundaries11 Oct 2022
- 2022Neural Networks are Decision Trees11 Oct 2022
- 2022Batch Normalization Explained29 Sep 2022
- 2022On the Number of Regions of Piecewise Linear Neural Networks17 Jun 2022
- 2022ExSpliNet: An interpretable and expressive spline-based neural network3 May 2022
- 2022Origami in N dimensions: How feed-forward networks manufacture linear separability21 Mar 2022
- 2022Over-parameterization: A Necessary Condition for Models that Extrapolate20 Mar 2022
- 2022Reverse Engineering ℓp attacks: A block-sparse optimization approach with recovery guarantees9 Mar 2022
- 2022Singular Value Perturbation and Deep Network Optimization7 Mar 2022
- 2022Polarity Sampling: Quality and Diversity Control of Pre-Trained Generative Networks via Singular Values3 Mar 2022
- 2022Decision boundaries and convex hulls in the feature space that deep learning functions learn from images5 Feb 2022
- 2022Manifoldron: Direct Space Partition via Manifold Discovery14 Jan 2022
- 2021Sparsest Univariate Learning Models Under Lipschitz Constraint27 Dec 2021
- 2021Error Bounds for a Matrix-Vector Product Approximation with Deep ReLU Neural Networks25 Nov 2021
- 2021Polynomial-Spline Neural Networks with Exact Integrals26 Oct 2021
- 2021Ortho-Shot: Low Displacement Rank Regularization with Data Augmentation for Few-Shot Learning18 Oct 2021
- 2021MaGNET: Uniform Sampling from Deep Generative Network Manifolds Without Retraining15 Oct 2021
50 newest of 55 All 55 (JSON)
- 2022Interpreting Neural Networks through the Polytope Lenscited by 33
- 2026Do Sparse Autoencoders Capture Concept Manifolds?cited by 31
- 2026Do Sparse Autoencoders Capture Concept Manifolds?30 Apr 2026
- 2022Interpreting Neural Networks through the Polytope Lens22 Nov 2022
- 2021CKConv: Continuous Kernel Convolution For Sequential Datacited by 120
- 2021What Kinds of Functions do Deep Neural Networks Learn? Insights from Variational Spline Theorycited by 60
- 2022Mechanistic Mode Connectivitycited by 50
- 2022ExSpliNet: An interpretable and expressive spline-based neural networkcited by 33
- 2021MaGNET: Uniform Sampling from Deep Generative Network Manifolds Without Retrainingcited by 23
- 2022Polarity Sampling: Quality and Diversity Control of Pre-Trained Generative Networks via Singular Valuescited by 21
- 2022On the Number of Regions of Piecewise Linear Neural Networkscited by 21
- 2023Deep Learning Meets Sparse Regularization: A Signal Processing Perspectivecited by 21
- 2022Neural Networks are Decision Treescited by 17
- 2023Polyhedral Complex Extraction from ReLU Networks using Edge Subdivisioncited by 14
- 2023Characterizing Large Language Model Geometry Helps Solve Toxicity Detection and Generationcited by 12
- 2022Singular Value Perturbation and Deep Network Optimizationcited by 11
12 most cited of 51 All 51 (JSON)
- 2026Hidden Activations are not Enough I: Knowledge Matrices as Higher Representations28 Sep 2026
- 2026Characterizing the Discrete Geometry of ReLU Networks5 Jun 2026
- 2026The Geometric Structure of Models Learning Sparse Data8 May 2026
- 2026The Linear Centroids Hypothesis: Features as Directions Learned by Local Experts13 Apr 2026
- 2026Divine Benevolence is an x2: GLUs scale asymptotically faster than MLPs16 Feb 2026
- 2026Poisson Hyperplane Processes with Rectified Linear Units9 Jan 2026
- 2025Concept Attractors in LLMs and their Applications30 Dec 2025
- 2025Non-Singularity of the Gradient Descent map for Neural Networks with Piecewise Analytic Activations28 Oct 2025
- 2025Computing Linear Regions in Neural Networks with Skip Connections18 Sep 2025
- 2025A Priori Generalizability Estimate for a CNN24 Feb 2025
- 2025Free-Knots Kolmogorov-Arnold Network: On the Analysis of Spline Knots and Advancing Stability16 Jan 2025
- 2025Semialgebraic Neural Networks: From roots to representations2 Jan 2025
12 newest of 51 All 51 (JSON)