Open-World Test-Time Adaptation with Hierarchical Feature Aggregation and Attention Affine

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Main Authors: Liu, Ziqiong, Tang, Yushun, Ji, Junyang, He, Zhihai
Format: Preprint
Published: 2025
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author Liu, Ziqiong
Tang, Yushun
Ji, Junyang
He, Zhihai
author_facet Liu, Ziqiong
Tang, Yushun
Ji, Junyang
He, Zhihai
contents Test-time adaptation (TTA) refers to adjusting the model during the testing phase to cope with changes in sample distribution and enhance the model's adaptability to new environments. In real-world scenarios, models often encounter samples from unseen (out-of-distribution, OOD) categories. Misclassifying these as known (in-distribution, ID) classes not only degrades predictive accuracy but can also impair the adaptation process, leading to further errors on subsequent ID samples. Many existing TTA methods suffer substantial performance drops under such conditions. To address this challenge, we propose a Hierarchical Ladder Network that extracts OOD features from class tokens aggregated across all Transformer layers. OOD detection performance is enhanced by combining the original model prediction with the output of the Hierarchical Ladder Network (HLN) via weighted probability fusion. To improve robustness under domain shift, we further introduce an Attention Affine Network (AAN) that adaptively refines the self-attention mechanism conditioned on the token information to better adapt to domain drift, thereby improving the classification performance of the model on datasets with domain shift. Additionally, a weighted entropy mechanism is employed to dynamically suppress the influence of low-confidence samples during adaptation. Experimental results on benchmark datasets show that our method significantly improves the performance on the most widely used classification datasets.
format Preprint
id arxiv_https___arxiv_org_abs_2511_12607
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Open-World Test-Time Adaptation with Hierarchical Feature Aggregation and Attention Affine
Liu, Ziqiong
Tang, Yushun
Ji, Junyang
He, Zhihai
Computer Vision and Pattern Recognition
Test-time adaptation (TTA) refers to adjusting the model during the testing phase to cope with changes in sample distribution and enhance the model's adaptability to new environments. In real-world scenarios, models often encounter samples from unseen (out-of-distribution, OOD) categories. Misclassifying these as known (in-distribution, ID) classes not only degrades predictive accuracy but can also impair the adaptation process, leading to further errors on subsequent ID samples. Many existing TTA methods suffer substantial performance drops under such conditions. To address this challenge, we propose a Hierarchical Ladder Network that extracts OOD features from class tokens aggregated across all Transformer layers. OOD detection performance is enhanced by combining the original model prediction with the output of the Hierarchical Ladder Network (HLN) via weighted probability fusion. To improve robustness under domain shift, we further introduce an Attention Affine Network (AAN) that adaptively refines the self-attention mechanism conditioned on the token information to better adapt to domain drift, thereby improving the classification performance of the model on datasets with domain shift. Additionally, a weighted entropy mechanism is employed to dynamically suppress the influence of low-confidence samples during adaptation. Experimental results on benchmark datasets show that our method significantly improves the performance on the most widely used classification datasets.
title Open-World Test-Time Adaptation with Hierarchical Feature Aggregation and Attention Affine
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2511.12607