提出可提前评估RBF-SVR优化收敛性的解析方法
Analytical Evaluation of DCA Convergence Properties for Minimizing Prediction Functions of Gaussian RBF Support Vector Regression

- 利用RBF核的解析结构构建显式DC分解
- 发现收敛性由单一标量 $C_αρ$ 完全决定
- 训练前可基于超参数预估优化性能,适合模型调优
针对使用高斯径向基函数核(RBF-SVR)的非凸优化问题,本文提出一种基于差分凸函数算法(DCA)的分析框架。通过解析挖掘RBF核结构,构造了显式的DC分解,并以闭式表达导出两个关键参数:子问题梯度Lipschitz常数上界 $L$ 与强凸参数下界 $μ$。二者均由训练后对偶系数和 $C_α$、核参数 $γ$ 及分解参数 $ρ$ 共同决定,且共享主导项 $C_αρ$。在六个基准函数上的数值实验表明,$C_αρ$ 是决定DCA收敛性和初值依赖性的核心变量,其变化可分解为 $C\to C_α$ 与 $γ\to ρ$ 两条独立路径,主控因素为SVR超参数 $(C, γ)$。因此,可通过 $C_αρ$ 在训练前估算收敛性(基于 $(C, γ)$),或在训练后精确计算,实现对RBF-SVR中DCA行为的预先评估。
原文摘要 · Abstract (English)
For nonconvex optimization problems whose objective is the prediction function of a trained Support Vector Regression (SVR) model with the Gaussian radial basis function (RBF) kernel (RBF-SVR), we present a framework that applies the difference of convex functions (DC) algorithm (DCA) by exploiting the analytical structure of the RBF kernel to construct an explicit DC decomposition. Specifically, we derive in closed form both the lower bound $μ$ of the strong convexity parameter of the DC components and the upper bound $L$ of the gradient Lipschitz constant of the subproblem. Both $μ$ and $L$ are determined solely by the post-training dual-coefficient sum $C_α$ and the RBF kernel parameter $γ$, together with the DC decomposition parameter $ρ$, and they share a common leading term $C_αρ$. Through numerical experiments on six benchmark functions, we show that $C_αρ$ is the primary single quantity characterizing both the convergence properties and the initial-point dependence of DCA, and further demonstrate that it decomposes into two independent pathways, $C \to C_α$ and $γ\to ρ$, with its primary variation governed by the SVR hyperparameters $(C, γ)$. Together, these results allow the convergence properties of DCA on RBF-SVR to be assessed in advance through the single scalar quantity $C_αρ$: approximately from $(C, γ)$ before training, and exactly in closed form after training.
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