A Rigorous, Tractable Measure of Model Complexity

Fuente: arXiv
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Auteurs principaux: Allerbo, Oskar, Schön, Thomas B.
Format: Preprint
Publié: 2026
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author Allerbo, Oskar
Schön, Thomas B.
author_facet Allerbo, Oskar
Schön, Thomas B.
contents An accurate assessment of a model's complexity is crucial for topics such as interpretation, generalization, and model selection. However, most existing complexity measures either rely on heuristic assumptions or are computationally prohibitive. In this paper, we present a mathematically rigorous yet easy-to-compute measure of model complexity that is based on the similarities between the model gradients across inputs. It is thus well-defined for any parametric model, but also for kernel-based non-parametric models. We prove that our measure of complexity generalizes model-specific complexity measures such as polynomial degree (for polynomial regression), kernel length scale (for Matérn kernels), number of neighbors (for k-nearest neighbors), number of splits (for decision trees), and number of trees (for random forests). We also use our measure to obtain new insights into the double descent phenomenon for random Fourier features, random forests, neural networks, and gradient boosting.
format Preprint
id arxiv_https___arxiv_org_abs_2605_21167
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A Rigorous, Tractable Measure of Model Complexity
Allerbo, Oskar
Schön, Thomas B.
Machine Learning
An accurate assessment of a model's complexity is crucial for topics such as interpretation, generalization, and model selection. However, most existing complexity measures either rely on heuristic assumptions or are computationally prohibitive. In this paper, we present a mathematically rigorous yet easy-to-compute measure of model complexity that is based on the similarities between the model gradients across inputs. It is thus well-defined for any parametric model, but also for kernel-based non-parametric models. We prove that our measure of complexity generalizes model-specific complexity measures such as polynomial degree (for polynomial regression), kernel length scale (for Matérn kernels), number of neighbors (for k-nearest neighbors), number of splits (for decision trees), and number of trees (for random forests). We also use our measure to obtain new insights into the double descent phenomenon for random Fourier features, random forests, neural networks, and gradient boosting.
title A Rigorous, Tractable Measure of Model Complexity
topic Machine Learning
url https://arxiv.org/abs/2605.21167