Algorithmic Separation between Constant-Depth and Logarithmic-Depth Neural Networks
- URL: http://arxiv.org/abs/2607.25200v1
- Date: Tue, 28 Jul 2026 02:13:30 GMT
- Title: Algorithmic Separation between Constant-Depth and Logarithmic-Depth Neural Networks
- Abstract summary: We prove the first algorithmic separation between constant-depth and logarithmic-depth networks.<n>Specifically, we identify a class of Boolean functions with hierarchically structured spectra that logarithmic-depth networks can learn efficiently.
- Score: 64.7580803923092
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Despite the empirical advantages of deep networks over shallow ones, theoretical depth separations largely concern approximation power, while algorithmic results are mostly limited to comparisons between two- and three-layer networks. In this work, we prove the first algorithmic separation between constant-depth and logarithmic-depth networks. Specifically, we identify a class of Boolean functions with hierarchically structured Fourier spectra that logarithmic-depth networks can learn efficiently using layerwise coordinate descent by reconstructing the spectra hierarchically and adaptively. We also exhibit a subclass for which every constant-depth, polynomial-width network with sufficiently regular activations and controlled spectral norms must incur constant $L^2$ approximation error under the uniform distribution over the hypercube.
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