Original Paper: https://arxiv.org/abs/2303.13283

By: Hantao Yao, Rui Zhang, Changsheng Xu

Abstract:

Prompt tuning is an effective way to adapt the pre-trained visual-language model (VLM) to the downstream task using task-related textual tokens. Representative CoOp-based work combines the learnable textual tokens with the class tokens to obtain specific textual knowledge. However, the specific textual knowledge is the worse generalization to the unseen classes because it forgets the essential general textual knowledge having a strong generalization ability. To tackle this issue, we introduce a novel Knowledge-guided Context Optimization (KgCoOp) to enhance the generalization ability of the learnable prompt for unseen classes. The key insight of KgCoOp is that forgetting about essential knowledge can be alleviated by reducing the discrepancy between the learnable prompt and the hand-crafted prompt. Especially, KgCoOp minimizes the discrepancy between the textual embeddings generated by learned prompts and the hand-crafted prompts. Finally, adding the KgCoOp upon the contrastive loss can make a discriminative prompt for both seen and unseen tasks. Extensive evaluation of several benchmarks demonstrates that the proposed Knowledge-guided Context Optimization is an efficient method for prompt tuning, \emph{i.e.,} achieves better performance with less training time.

Summary Notes

Optimizing Visual-Language Models with Knowledge-Guided Context

Introduction

Visual-Language Models (VLMs) have significantly advanced AI's ability to process and analyze the relationship between images and text.

These models, after being trained on numerous image-text pairs, have become key players in areas like image captioning and visual question answering.

However, fine-tuning these models for specific tasks can be challenging due to their fixed architectures and the lack of specialized data.

Prompt tuning has emerged as a solution, offering a way to adapt VLMs to specific needs without extensive retraining. Yet, it struggles with generalizing to new, unseen categories.

We introduce a new technique, Knowledge-guided Context Optimization (KgCoOp), to address these limitations, making VLM customization more efficient and adaptable.

Background

Models such as CLIP and ALIGN are known for their ability to generalize, performing zero-shot learning by classifying images into new categories without direct training.

Prompt tuning enhances this by modifying textual prompts to fit particular tasks, but this approach has its flaws, particularly with adapting to unseen classes.

KgCoOp Approach

KgCoOp aims to fill this gap by ensuring a balance between task-specific knowledge and a broad textual understanding.

It reduces the difference between the embeddings from customized prompts and those from generic, unaltered prompts.

The key here is to minimize the performance gap on new classes by introducing a constraint that penalizes the distance between these two types of embeddings, promoting a balance that improves the model's generalization ability.

Testing and Results

KgCoOp was rigorously evaluated against standard models and methods, showing its edge in adapting VLMs to new categories and in training efficiency.

Through tests that covered a range of tasks, KgCoOp consistently topped other methods, showcasing its potential in both generalization and training speed.

Conclusion

KgCoOp marks a significant advancement in adapting visual-language models to new tasks, particularly with its focus on generalizing to unseen classes.

By smartly balancing task-specific prompts with general knowledge, it not only makes VLMs more adaptable but also more efficient.

Future work could further enhance this balance, expanding the potential applications of VLMs.

Visual Comparisons

The comparative analysis, illustrated through tables and figures, clearly demonstrates KgCoOp's superior performance across various tests, highlighting its advantages in efficiency and effectiveness over existing methods.

Final Thoughts

KgCoOp's strategy of optimizing for specific contexts while retaining a grasp on general textual knowledge represents a crucial development in prompt tuning.

Its compatibility with existing VLM frameworks means it can be easily integrated into current models, boosting their performance across a wide range of tasks.