Approximating invariant functions with the sorting trick is theoretically justified

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Hauptverfasser: Chaimanowong, Wee, Zhu, Ying
Format: Preprint
Veröffentlicht: 2024
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author Chaimanowong, Wee
Zhu, Ying
author_facet Chaimanowong, Wee
Zhu, Ying
contents Many machine learning models leverage group invariance which is enjoyed with a wide-range of applications. For exploiting an invariance structure, one common approach is known as \emph{frame averaging}. One popular example of frame averaging is the \emph{group averaging}, where the entire group is used to symmetrize a function. Another example is the \emph{canonicalization}, where a frame at each point consists of a single group element which transforms the point to its orbit representative, for example, sorting. Compared to group averaging, canonicalization is more efficient computationally. However, it results in non-differentiablity or discontinuity of the canonicalized function. As a result, the theoretical performance of canonicalization has not been given much attention. In this work, we establish an approximation theory for canonicalization. Specifically, we bound the point-wise and $L^2(\mathbb{P})$ approximation errors as well as the eigenvalue decay rates associated with a canonicalization trick applied to reproducing kernels. We discuss two key insights from our theoretical analyses and why they point to an interesting future research direction on how one can choose a design to fully leverage canonicalization in practice.
format Preprint
id arxiv_https___arxiv_org_abs_2403_01671
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Approximating invariant functions with the sorting trick is theoretically justified
Chaimanowong, Wee
Zhu, Ying
Machine Learning
65G05 (Primary), 20B99 (Secondary)
Many machine learning models leverage group invariance which is enjoyed with a wide-range of applications. For exploiting an invariance structure, one common approach is known as \emph{frame averaging}. One popular example of frame averaging is the \emph{group averaging}, where the entire group is used to symmetrize a function. Another example is the \emph{canonicalization}, where a frame at each point consists of a single group element which transforms the point to its orbit representative, for example, sorting. Compared to group averaging, canonicalization is more efficient computationally. However, it results in non-differentiablity or discontinuity of the canonicalized function. As a result, the theoretical performance of canonicalization has not been given much attention. In this work, we establish an approximation theory for canonicalization. Specifically, we bound the point-wise and $L^2(\mathbb{P})$ approximation errors as well as the eigenvalue decay rates associated with a canonicalization trick applied to reproducing kernels. We discuss two key insights from our theoretical analyses and why they point to an interesting future research direction on how one can choose a design to fully leverage canonicalization in practice.
title Approximating invariant functions with the sorting trick is theoretically justified
topic Machine Learning
65G05 (Primary), 20B99 (Secondary)
url https://arxiv.org/abs/2403.01671