Inexact Simplification of Symbolic Regression Expressions with Locality-sensitive Hashing

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Auteurs principaux: Aldeia, Guilherme Seidyo Imai, de Franca, Fabricio Olivetti, La Cava, William G.
Format: Preprint
Publié: 2024
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author Aldeia, Guilherme Seidyo Imai
de Franca, Fabricio Olivetti
La Cava, William G.
author_facet Aldeia, Guilherme Seidyo Imai
de Franca, Fabricio Olivetti
La Cava, William G.
contents Symbolic regression (SR) searches for parametric models that accurately fit a dataset, prioritizing simplicity and interpretability. Despite this secondary objective, studies point out that the models are often overly complex due to redundant operations, introns, and bloat that arise during the iterative process, and can hinder the search with repeated exploration of bloated segments. Applying a fast heuristic algebraic simplification may not fully simplify the expression and exact methods can be infeasible depending on size or complexity of the expressions. We propose a novel agnostic simplification and bloat control for SR employing an efficient memoization with locality-sensitive hashing (LHS). The idea is that expressions and their sub-expressions traversed during the iterative simplification process are stored in a dictionary using LHS, enabling efficient retrieval of similar structures. We iterate through the expression, replacing subtrees with others of same hash if they result in a smaller expression. Empirical results shows that applying this simplification during evolution performs equal or better than without simplification in minimization of error, significantly reducing the number of nonlinear functions. This technique can learn simplification rules that work in general or for a specific problem, and improves convergence while reducing model complexity.
format Preprint
id arxiv_https___arxiv_org_abs_2404_05898
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Inexact Simplification of Symbolic Regression Expressions with Locality-sensitive Hashing
Aldeia, Guilherme Seidyo Imai
de Franca, Fabricio Olivetti
La Cava, William G.
Neural and Evolutionary Computing
Machine Learning
Symbolic regression (SR) searches for parametric models that accurately fit a dataset, prioritizing simplicity and interpretability. Despite this secondary objective, studies point out that the models are often overly complex due to redundant operations, introns, and bloat that arise during the iterative process, and can hinder the search with repeated exploration of bloated segments. Applying a fast heuristic algebraic simplification may not fully simplify the expression and exact methods can be infeasible depending on size or complexity of the expressions. We propose a novel agnostic simplification and bloat control for SR employing an efficient memoization with locality-sensitive hashing (LHS). The idea is that expressions and their sub-expressions traversed during the iterative simplification process are stored in a dictionary using LHS, enabling efficient retrieval of similar structures. We iterate through the expression, replacing subtrees with others of same hash if they result in a smaller expression. Empirical results shows that applying this simplification during evolution performs equal or better than without simplification in minimization of error, significantly reducing the number of nonlinear functions. This technique can learn simplification rules that work in general or for a specific problem, and improves convergence while reducing model complexity.
title Inexact Simplification of Symbolic Regression Expressions with Locality-sensitive Hashing
topic Neural and Evolutionary Computing
Machine Learning
url https://arxiv.org/abs/2404.05898