Enhancing Zero-Shot Vision Models by Label-Free Prompt Distribution Learning and Bias Correcting

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Main Authors: Zhu, Xingyu, Zhu, Beier, Tan, Yi, Wang, Shuo, Hao, Yanbin, Zhang, Hanwang
Format: Preprint
Published: 2024
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author Zhu, Xingyu
Zhu, Beier
Tan, Yi
Wang, Shuo
Hao, Yanbin
Zhang, Hanwang
author_facet Zhu, Xingyu
Zhu, Beier
Tan, Yi
Wang, Shuo
Hao, Yanbin
Zhang, Hanwang
contents Vision-language models, such as CLIP, have shown impressive generalization capacities when using appropriate text descriptions. While optimizing prompts on downstream labeled data has proven effective in improving performance, these methods entail labor costs for annotations and are limited by their quality. Additionally, since CLIP is pre-trained on highly imbalanced Web-scale data, it suffers from inherent label bias that leads to suboptimal performance. To tackle the above challenges, we propose a label-Free prompt distribution learning and bias correction framework, dubbed as **Frolic**, which boosts zero-shot performance without the need for labeled data. Specifically, our Frolic learns distributions over prompt prototypes to capture diverse visual representations and adaptively fuses these with the original CLIP through confidence matching. This fused model is further enhanced by correcting label bias via a label-free logit adjustment. Notably, our method is not only training-free but also circumvents the necessity for hyper-parameter tuning. Extensive experimental results across 16 datasets demonstrate the efficacy of our approach, particularly outperforming the state-of-the-art by an average of $2.6\%$ on 10 datasets with CLIP ViT-B/16 and achieving an average margin of $1.5\%$ on ImageNet and its five distribution shifts with CLIP ViT-B/16. Codes are available in https://github.com/zhuhsingyuu/Frolic.
format Preprint
id arxiv_https___arxiv_org_abs_2410_19294
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Enhancing Zero-Shot Vision Models by Label-Free Prompt Distribution Learning and Bias Correcting
Zhu, Xingyu
Zhu, Beier
Tan, Yi
Wang, Shuo
Hao, Yanbin
Zhang, Hanwang
Computer Vision and Pattern Recognition
Vision-language models, such as CLIP, have shown impressive generalization capacities when using appropriate text descriptions. While optimizing prompts on downstream labeled data has proven effective in improving performance, these methods entail labor costs for annotations and are limited by their quality. Additionally, since CLIP is pre-trained on highly imbalanced Web-scale data, it suffers from inherent label bias that leads to suboptimal performance. To tackle the above challenges, we propose a label-Free prompt distribution learning and bias correction framework, dubbed as **Frolic**, which boosts zero-shot performance without the need for labeled data. Specifically, our Frolic learns distributions over prompt prototypes to capture diverse visual representations and adaptively fuses these with the original CLIP through confidence matching. This fused model is further enhanced by correcting label bias via a label-free logit adjustment. Notably, our method is not only training-free but also circumvents the necessity for hyper-parameter tuning. Extensive experimental results across 16 datasets demonstrate the efficacy of our approach, particularly outperforming the state-of-the-art by an average of $2.6\%$ on 10 datasets with CLIP ViT-B/16 and achieving an average margin of $1.5\%$ on ImageNet and its five distribution shifts with CLIP ViT-B/16. Codes are available in https://github.com/zhuhsingyuu/Frolic.
title Enhancing Zero-Shot Vision Models by Label-Free Prompt Distribution Learning and Bias Correcting
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2410.19294