← 研踪 PaperTrailarXiv:2610.37737 · v1
Anisotropic Trust Region Warping for Prior-Data Fitted Networks in Bayesian Optimisation
首次提交 2026-10-27 22:58
版本更新 2026-10-27 22:58
雷达观测 2026-10-30 10:23
摘要
Prior-Data Fitted Networks (PFNs) replace the hyperparameter refitting of Gaussian Process (GP) surrogates in Bayesian optimisation with a single forward pass, at the cost of a prior that is fixed at meta-training time. We show empirically that a PFN's predictive log-likelihood falls increasingly behind that of a refitted GP as the objective function's lengthscale grows beyond the mode of the PFN's meta-training prior, and that this deficit carries over to optimisation performance. To correct the mismatch without retraining the network, we introduce Anisotropic Trust Region (ATR) warping. Per-dimension lengthscales are estimated by kernel target alignment, and an affine rescaling of the input space maps the objective onto the lengthscale the PFN expects, with a trust region around the anchor determining which observations are retained, leaving the PFN's $\mathcal{O}(d \cdot N^2)$ inference cost unchanged. On functions drawn from a Matérn-3/2 kernel, ATR warping improves optimisation performance of the PFN at both extremes of the lengthscale range. Our implementation is publicly available at https://github.com/youngers2006/Trust-Region-Warping-For-PFNs.
作者备注：Accepted at the 2026 NeurIPS Workshop on Optimization for Machine Learning (OPT). 18 pages, 12 figures
观测到的版本
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v1 · 2026-10-27 22:58 · 最新观测版本
Anisotropic Trust Region Warping for Prior-Data Fitted Networks in Bayesian Optimisation
Prior-Data Fitted Networks (PFNs) replace the hyperparameter refitting of Gaussian Process (GP) surrogates in Bayesian optimisation with a single forward pass, at the cost of a prior that is fixed at meta-training time. We show empirically that a PFN's predictive log-likelihood falls increasingly behind that of a refitted GP as the objective function's lengthscale grows beyond the mode of the PFN's meta-training prior, and that this deficit carries over to optimisation performance. To correct the mismatch without retraining the network, we introduce Anisotropic Trust Region (ATR) warping. Per-dimension lengthscales are estimated by kernel target alignment, and an affine rescaling of the input space maps the objective onto the lengthscale the PFN expects, with a trust region around the anchor determining which observations are retained, leaving the PFN's $\mathcal{O}(d \cdot N^2)$ inference cost unchanged. On functions drawn from a Matérn-3/2 kernel, ATR warping improves optimisation performance of the PFN at both extremes of the lengthscale range. Our implementation is publicly available at https://github.com/youngers2006/Trust-Region-Warping-For-PFNs.
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