When Good Equations Get Bad Scores: Improving Symbolic Regression Through Better Parameter Optimization

Fuente: arXiv
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Main Authors: Wang, Boxiao, Li, Kai, Chen, Zhiwei, Huang, Yang, Wang, Runxiang, Zhang, Ziwen, Zhang, Yifan, Cheng, Jian
Format: Preprint
Published: 2026
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_version_ 1866913155017342976
author Wang, Boxiao
Li, Kai
Chen, Zhiwei
Huang, Yang
Wang, Runxiang
Zhang, Ziwen
Zhang, Yifan
Cheng, Jian
author_facet Wang, Boxiao
Li, Kai
Chen, Zhiwei
Huang, Yang
Wang, Runxiang
Zhang, Ziwen
Zhang, Yifan
Cheng, Jian
contents Symbolic Regression (SR) plays a central role in scientific knowledge discovery by distilling mathematical equations from observational data. Most existing SR methods function within a bi-level optimization framework: an outer loop that searches for the discrete equation structure, and an inner loop that optimizes the continuous parameters of that structure. Crucially, parameter-fitting quality directly determines a structure's score and thus the outer-loop search. However, nonlinear operators make the inner loop highly non-convex, and budget-driven reliance on fast local solvers (e.g., BFGS) often yields poor local minima and underestimated scores for correct structures. This ``Good Structure, Bad Score'' phenomenon becomes a key bottleneck, degrading efficiency and misguiding the search away from the true equation. To resolve this, we propose SAGE-Fit (Structure-Aware and Semantics-Guided Evaluator for Symbolic Regression), an SR-native fitting framework that exploits the dual native priors of symbolic expressions. By capitalizing on the structural and semantic priors unique to SR, we design tailored modules for each property, thereby effectively mitigating this optimization bottleneck. Extensive experiments demonstrate that our approach, as a plug-and-play module, significantly enhances evaluation fidelity and universally improves the performance of various SR systems.
format Preprint
id arxiv_https___arxiv_org_abs_2605_23272
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle When Good Equations Get Bad Scores: Improving Symbolic Regression Through Better Parameter Optimization
Wang, Boxiao
Li, Kai
Chen, Zhiwei
Huang, Yang
Wang, Runxiang
Zhang, Ziwen
Zhang, Yifan
Cheng, Jian
Machine Learning
Artificial Intelligence
Symbolic Regression (SR) plays a central role in scientific knowledge discovery by distilling mathematical equations from observational data. Most existing SR methods function within a bi-level optimization framework: an outer loop that searches for the discrete equation structure, and an inner loop that optimizes the continuous parameters of that structure. Crucially, parameter-fitting quality directly determines a structure's score and thus the outer-loop search. However, nonlinear operators make the inner loop highly non-convex, and budget-driven reliance on fast local solvers (e.g., BFGS) often yields poor local minima and underestimated scores for correct structures. This ``Good Structure, Bad Score'' phenomenon becomes a key bottleneck, degrading efficiency and misguiding the search away from the true equation. To resolve this, we propose SAGE-Fit (Structure-Aware and Semantics-Guided Evaluator for Symbolic Regression), an SR-native fitting framework that exploits the dual native priors of symbolic expressions. By capitalizing on the structural and semantic priors unique to SR, we design tailored modules for each property, thereby effectively mitigating this optimization bottleneck. Extensive experiments demonstrate that our approach, as a plug-and-play module, significantly enhances evaluation fidelity and universally improves the performance of various SR systems.
title When Good Equations Get Bad Scores: Improving Symbolic Regression Through Better Parameter Optimization
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2605.23272