Adversarially Adaptive Normalization for Single Domain Generalization
Single domain generalization aims to learn a model that performs well on many unseen domains with only one domain data for training. Existing works focus on studying the adversarial domain augmentation (ADA) to improve the model's generalization capability. The impact on domain generalization of the statistics of normalization layers is still underinvestigated. In this paper, we propose a generic normalization approach, adaptive standardization and rescaling normalization (ASR Norm) to complement the missing part in previous works. ASR Norm learns both the standardization and rescaling statistics via neural networks. This new form of normalization can be viewed as a generic form of the traditional normalizations. When trained with ADA, the statistics in ASR Norm are learned to be adaptive to the data coming from different domains, and hence improves the model generalization performance across domains, especially on the target domain with large discrepancy from the source domain. The experimental results show that ASR Norm can bring consistent improvement to the state of the art ADA approaches by 1.6% 2.7% and 6.3% averagely on the Digits, CIFAR 10 C, and PACS benchmarks, respectively. As a generic tool, the improvement introduced by ASR Norm is agnostic to the choice of ADA methods.
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