Nemesis: Normalizing the Soft-prompt Vectors of Vision-Language Models

Published: 16 Jan 2024, Last Modified: 15 Mar 2024ICLR 2024 spotlightEveryoneRevisionsBibTeX
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Keywords: Vision-language models; Soft-prompt tuning; Low-norm effect; Normalizing soft prompts
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TL;DR: This paper first uncovers a Low-Norm Effect phenomenon that occurs in soft prompt-tuning vision-language models (VLMs) and proposes a method for normalizing the soft prompts of VLMs to achieve better performance.
Abstract: With the prevalence of large-scale pretrained vision-language models (VLMs), such as CLIP, soft-prompt tuning has become a popular method for adapting these models to various downstream tasks. However, few works delve into the inherent properties of learnable soft-prompt vectors, specifically the impact of their norms to the performance of VLMs. This motivates us to pose an unexplored research question: ``Do we need to normalize the soft prompts in VLMs?'' To fill this research gap, we first uncover a phenomenon, called the $\textbf{Low-Norm Effect}$ by performing extensive corruption experiments, suggesting that reducing the norms of certain learned prompts occasionally enhances the performance of VLMs, while increasing them often degrades it. To harness this effect, we propose a novel method named $\textbf{N}$ormalizing th$\textbf{e}$ soft-pro$\textbf{m}$pt v$\textbf{e}$ctors of vi$\textbf{si}$on-language model$\textbf{s}$ ($\textbf{Nemesis}$) to normalize soft-prompt vectors in VLMs. To the best of our knowledge, our work is the first to systematically investigate the role of norms of soft-prompt vector in VLMs, offering valuable insights for future research in soft-prompt tuning.
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Primary Area: unsupervised, self-supervised, semi-supervised, and supervised representation learning
Submission Number: 7114