The Geometric Structure of Fully-Connected ReLU Layers
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Abstract (arXiv)
We formalize and interpret the geometric structure of d-dimensional fully connected ReLU layers in neural networks. The parameters of a ReLU layer induce a natural partition of the input domain, such that the ReLU layer can be significantly simplified in each sector of the partition. This leads to a geometric interpretation of a ReLU layer as a projection onto a polyhedral cone followed by an affine transformation, in line with the description in [doi:10.48550/arXiv.1905.08922] for convolutional networks with ReLU activations. Further, this structure facilitates simplified expressions for preimages of the intersection between partition sectors and hyperplanes, which is useful when describing decision boundaries in a classification setting. We investigate this in detail for a feed-forward network with one hidden ReLU-layer, where we provide results on the geometric complexity of the decision boundary generated by such networks, as well as proving that modulo an affine transformation, such a network can only generate d different decision boundaries. Finally, the effect of adding more layers to the network is discussed.
Key facts. Cited by 4 papers in the map (data through 7 Oct 2026). Builds on 11 of its 18 references that are in the map. First posted on arXiv 5 Oct 2023.
Builds on
11 of 18 references.
References · 11
- 2014On the Number of Linear Regions of Deep Neural Networkscited by 378
- 2013Maxout Networkscited by 186
- 2018Robustness via curvature regularization, and vice versacited by 174
- 2019Deep ReLU Networks Have Surprisingly Few Activation Patternscited by 160
- 2021Activation Functions in Deep Learning: A Comprehensive Survey and Benchmarkcited by 153
- 2017Approximating Continuous Functions by ReLU Nets of Minimal Widthcited by 120
- 2020Topology of deep neural networkscited by 111
- 2018Tropical Geometry of Deep Neural Networkscited by 92
- 2020On the Decision Boundaries of Neural Networks: A Tropical Geometry Perspectivecited by 25
- 2016Efficient Representation of Low-Dimensional Manifolds using Deep Networkscited by 13
- 2019Geometry of Deep Convolutional Networkscited by 4
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Citing papers per year: 2024: 2; 2025: 2.
4 papers.
- 2025Marching Neurons: Accurate Surface Extraction for Neural Implicit Shapescited by 3
- 2024Defining Neural Network Architecture through Polytope Structures of Datasetcited by 2
- 2024Implicit Hypersurface Approximation Capacity in Deep ReLU Networkscited by 0
- 2025Explicit neural network classifiers for non-separable datacited by 0
- 2025Marching Neurons: Accurate Surface Extraction for Neural Implicit Shapes25 Sep 2025
- 2025Explicit neural network classifiers for non-separable data25 Apr 2025
- 2024Implicit Hypersurface Approximation Capacity in Deep ReLU Networks4 Jul 2024
- 2024Defining Neural Network Architecture through Polytope Structures of Dataset4 Feb 2024