发现扩散模型蒸馏中控制性能的核心是提示增广,而非分布匹配。
Decoupled DMD: CFG Augmentation as the Spear, Distribution Matching as the Shield

- 将蒸馏目标拆解为提示增广与分布匹配两部分,揭示前者为主引擎。
- 分布匹配仅起稳定训练作用,可被其他简单约束替代。
- 新方法提升生成质量,已用于顶级8步图像生成模型开发。
扩散模型蒸馏已成为高效少步和单步生成器的关键技术。其中,分布匹配蒸馏(DMD)及其变体表现优异,通常归因于其使学生模型输出分布匹配教师模型的机制。本文通过严格分解DMD训练目标,发现复杂任务如文生图中,少步蒸馏的主要驱动力并非分布匹配,而是此前被忽视的提示增广(CA)成分。我们证明该成分是蒸馏的核心“引擎”,而分布匹配(DM)则作为“正则项”保障训练稳定并减少伪影。进一步验证表明,尽管DM是有效正则,但非唯一选择;更简单的非参数约束或GAN目标也可实现类似稳定效果,仅存在权衡差异。此解耦促使对两者的系统性分析,进而提出合理修改,如解耦引擎与正则项的噪声调度,获得性能提升。本方法已被Z-Image项目采用,用于开发顶尖8步图像生成模型,实证验证了结论的泛化性与鲁棒性。
原文摘要 · Abstract (English)
Diffusion model distillation has emerged as a powerful technique for creating efficient few-step and single-step generators. Among these, Distribution Matching Distillation (DMD) and its variants stand out for their impressive performance, which is widely attributed to their core mechanism of matching the student's output distribution to that of a pre-trained teacher model. In this work, we challenge this conventional understanding. Through a rigorous decomposition of the DMD training objective, we reveal that in complex tasks like text-to-image generation, where CFG is typically required for desirable few-step performance, the primary driver of few-step distillation is not distribution matching, but a previously overlooked component we identify as CFG Augmentation (CA). We demonstrate that this term acts as the core ``engine'' of distillation, while the Distribution Matching (DM) term functions as a ``regularizer'' that ensures training stability and mitigates artifacts. We further validate this decoupling by demonstrating that while the DM term is a highly effective regularizer, it is not unique; simpler non-parametric constraints or GAN-based objectives can serve the same stabilizing function, albeit with different trade-offs. This decoupling of labor motivates a more principled analysis of the properties of both terms, leading to a more systematic and in-depth understanding. This new understanding further enables us to propose principled modifications to the distillation process, such as decoupling the noise schedules for the engine and the regularizer, leading to further performance gains. Notably, our method has been adopted by the Z-Image ( https://github.com/Tongyi-MAI/Z-Image ) project to develop a top-tier 8-step image generation model, empirically validating the generalization and robustness of our findings.
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