DPOK: Reinforcement Learning for Fine-tuning Text-to-Image Diffusion Models
This work addresses the problem of enhancing text-to-image generation for AI applications, representing an incremental improvement over existing fine-tuning techniques.
The authors tackled the challenge of fine-tuning text-to-image diffusion models using human feedback by proposing DPOK, an online reinforcement learning method with KL regularization, which outperformed supervised fine-tuning in improving image-text alignment and image quality.
Learning from human feedback has been shown to improve text-to-image models. These techniques first learn a reward function that captures what humans care about in the task and then improve the models based on the learned reward function. Even though relatively simple approaches (e.g., rejection sampling based on reward scores) have been investigated, fine-tuning text-to-image models with the reward function remains challenging. In this work, we propose using online reinforcement learning (RL) to fine-tune text-to-image models. We focus on diffusion models, defining the fine-tuning task as an RL problem, and updating the pre-trained text-to-image diffusion models using policy gradient to maximize the feedback-trained reward. Our approach, coined DPOK, integrates policy optimization with KL regularization. We conduct an analysis of KL regularization for both RL fine-tuning and supervised fine-tuning. In our experiments, we show that DPOK is generally superior to supervised fine-tuning with respect to both image-text alignment and image quality. Our code is available at https://github.com/google-research/google-research/tree/master/dpok.