Bi-Level Optimization for Single Domain Generalization

Fuente: arXiv
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Auteurs principaux: Heidari, Marzi, Zhang, Hanping, Yan, Hao, Guo, Yuhong
Format: Preprint
Publié: 2026
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author Heidari, Marzi
Zhang, Hanping
Yan, Hao
Guo, Yuhong
author_facet Heidari, Marzi
Zhang, Hanping
Yan, Hao
Guo, Yuhong
contents Generalizing from a single labeled source domain to unseen target domains, without access to any target data during training, remains a fundamental challenge in robust machine learning. We address this underexplored setting, known as Single Domain Generalization (SDG), by proposing BiSDG, a bi-level optimization framework that explicitly decouples task learning from domain modeling. BiSDG simulates distribution shifts through surrogate domains constructed via label-preserving transformations of the source data. To capture domain-specific context, we propose a domain prompt encoder that generates lightweight modulation signals to produce augmenting features via feature-wise linear modulation. The learning process is formulated as a bi-level optimization problem: the inner objective optimizes task performance under fixed prompts, while the outer objective maximizes generalization across the surrogate domains by updating the domain prompt encoder. We further develop a practical gradient approximation scheme that enables efficient bi-level training without second-order derivatives. Extensive experiments on various SGD benchmarks demonstrate that BiSDG consistently outperforms prior methods, setting new state-of-the-art performance in the SDG setting.
format Preprint
id arxiv_https___arxiv_org_abs_2604_06349
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Bi-Level Optimization for Single Domain Generalization
Heidari, Marzi
Zhang, Hanping
Yan, Hao
Guo, Yuhong
Machine Learning
Artificial Intelligence
Computer Vision and Pattern Recognition
Generalizing from a single labeled source domain to unseen target domains, without access to any target data during training, remains a fundamental challenge in robust machine learning. We address this underexplored setting, known as Single Domain Generalization (SDG), by proposing BiSDG, a bi-level optimization framework that explicitly decouples task learning from domain modeling. BiSDG simulates distribution shifts through surrogate domains constructed via label-preserving transformations of the source data. To capture domain-specific context, we propose a domain prompt encoder that generates lightweight modulation signals to produce augmenting features via feature-wise linear modulation. The learning process is formulated as a bi-level optimization problem: the inner objective optimizes task performance under fixed prompts, while the outer objective maximizes generalization across the surrogate domains by updating the domain prompt encoder. We further develop a practical gradient approximation scheme that enables efficient bi-level training without second-order derivatives. Extensive experiments on various SGD benchmarks demonstrate that BiSDG consistently outperforms prior methods, setting new state-of-the-art performance in the SDG setting.
title Bi-Level Optimization for Single Domain Generalization
topic Machine Learning
Artificial Intelligence
Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2604.06349