How to Learn a Star: Binary Classification with Starshaped Polyhedral Sets

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Hauptverfasser: Brandenburg, Marie-Charlotte, Jochemko, Katharina
Format: Preprint
Veröffentlicht: 2025
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author Brandenburg, Marie-Charlotte
Jochemko, Katharina
author_facet Brandenburg, Marie-Charlotte
Jochemko, Katharina
contents We consider binary classification restricted to a class of continuous piecewise linear functions whose decision boundaries are (possibly nonconvex) starshaped polyhedral sets, supported on a fixed polyhedral simplicial fan. We investigate the expressivity of these function classes and describe the combinatorial and geometric structure of the loss landscape, most prominently the sublevel sets, for two loss-functions: the 0/1-loss (discrete loss) and a log-likelihood loss function. In particular, we give explicit bounds on the VC dimension of this model, and concretely describe the sublevel sets of the discrete loss as chambers in a hyperplane arrangement. For the log-likelihood loss, we give sufficient conditions for the optimum to be unique, and describe the geometry of the optimum when varying the rate parameter of the underlying exponential probability distribution.
format Preprint
id arxiv_https___arxiv_org_abs_2505_01346
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle How to Learn a Star: Binary Classification with Starshaped Polyhedral Sets
Brandenburg, Marie-Charlotte
Jochemko, Katharina
Machine Learning
Discrete Mathematics
Combinatorics
Metric Geometry
We consider binary classification restricted to a class of continuous piecewise linear functions whose decision boundaries are (possibly nonconvex) starshaped polyhedral sets, supported on a fixed polyhedral simplicial fan. We investigate the expressivity of these function classes and describe the combinatorial and geometric structure of the loss landscape, most prominently the sublevel sets, for two loss-functions: the 0/1-loss (discrete loss) and a log-likelihood loss function. In particular, we give explicit bounds on the VC dimension of this model, and concretely describe the sublevel sets of the discrete loss as chambers in a hyperplane arrangement. For the log-likelihood loss, we give sufficient conditions for the optimum to be unique, and describe the geometry of the optimum when varying the rate parameter of the underlying exponential probability distribution.
title How to Learn a Star: Binary Classification with Starshaped Polyhedral Sets
topic Machine Learning
Discrete Mathematics
Combinatorics
Metric Geometry
url https://arxiv.org/abs/2505.01346