PrePrompt: Predictive Prompting for Class Incremental Learning

Abstract

Prompt-based learning has emerged as a promising paradigm for Class Incremental Learning (CIL), enabling pre-trained models to adapt efficiently to open-world scenarios. Existing methods often employ correlation-based strategies, where an image's feature serves as a query to retrieve the most relevant key prompts, with corresponding value prompts for training. However, these approaches face a fundamental challenge: fitting the entire feature space of all tasks with only a few trainable prompts severely limits the pre-trained model's retrieval capability. In this paper, we propose Predictive Prompting (PrePrompt), a novel CIL framework that circumvents correlation-based limitations by leveraging the inherent classification ability of pre-trained models to predict task-specific prompts. Specifically, PrePrompt decomposes CIL into a two-stage prediction process: task-specific prompt prediction followed by a label prediction. While theoretically sound, this framework risks bias toward recent classes due to missing historical information for calibrating older classifiers. To mitigate this, PrePrompt incorporates a feature extrapolation technique, dynamically balancing stability and plasticity across classifiers. Extensive experiments on several benchmarks demonstrate PrePrompt's superiority over state-of-the-art prompt-based CIL methods. Code is available at https://github.com/libo-huang/preprompt.