Seeking Global Flat Minima in Federated Domain Generalization via Constrained Adversarial Augmentation

ICLR 2025 Conference Submission10017 Authors

Keywords: Federated Domain Generalization, Flat Minima, Data Augmentation

Abstract: Federated domain generalization (FedDG) aims at equipping the federally trained model with the domain generalization ability when the model meets new clients with domain shifts. Among factors that possibly indicate generalization, the loss landscape flatness of the trained model is an intuitive, viable, and widely studied one. However, pursuing the flatness of the global model in the FedDG setting is not trivial due to the restriction to preserve data privacy. To address this issue, we propose GFM, a novel algorithm designed to seek Global Flat Minima of the global model. Specifically, GFM leverages a global model-constrained adversarial data augmentation strategy, creating a surrogate for global data within each local client, which allows for split sharpness-aware minimization to approach global flat minima. GFM is compatible with federated learning without compromising data privacy restrictions, and theoretical analysis further supports its rationality by demonstrating that the objective of GFM serves as an upper bound on the robust risk of the global model on global data distribution. Extensive experiments on multiple FedDG benchmarks demonstrate that GFM consistently outperforms previous FedDG and federated learning approaches.

Primary Area: applications to computer vision, audio, language, and other modalities

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Submission Number: 10017