通过分时分配关键词更新时机,解决扩散语言模型编辑失效问题。
Don't Let It Fade: Preserving Edits in Diffusion Language Models via Token Timestep Allocation
- 为每个词分配不同更新时间,关键词早冻结,不确定词持续优化。
- 情感控制准确率提升20%以上,困惑度降低近一半,仅需不足1/5步数。
- 适用于多种模型和任务,无需训练,适合需要精准编辑的场景。
虽然扩散语言模型(DLMs)支持细粒度编辑,但其可控性仍易失效。我们识别并形式化了一种核心失败模式——更新遗忘:均匀且无上下文依赖的更新导致词级别波动,使早期语义编辑被抹除,破坏累积优化过程,降低流畅性和连贯性。该问题源于更新的均匀与上下文无关,有效控制需显式词序。我们提出令牌时间分配(TTA),通过每词的时间调度实现软性语义排序:关键词早期冻结,不确定词持续优化。该时间排序可固定或由任务信号自适应驱动,支持多样编辑策略。因仅在推理时运行,适用于各类DLM,自然扩展至多源监督。实验显示,TTA显著提升可控性与流畅性:情感控制下准确率提升超20%,困惑度减半,步骤少于1/5;去毒化中最大毒性降至12.2(原14.5),困惑度26.0(原32.0)。结果表明,基于时间分配的软排序是缓解更新遗忘、实现稳定可控扩散文本生成的关键。
原文摘要 · Abstract (English)
While diffusion language models (DLMs) enable fine-grained refinement, their practical controllability remains fragile. We identify and formally characterize a central failure mode called update forgetting, in which uniform and context agnostic updates induce token level fluctuations across timesteps, erasing earlier semantic edits and disrupting the cumulative refinement process, thereby degrading fluency and coherence. As this failure originates in uniform and context agnostic updates, effective control demands explicit token ordering. We propose Token Timestep Allocation (TTA), which realizes soft and semantic token ordering via per token timestep schedules: critical tokens are frozen early, while uncertain tokens receive continued refinement. This timestep based ordering can be instantiated as either a fixed policy or an adaptive policy driven by task signals, thereby supporting a broad spectrum of refinement strategies. Because it operates purely at inference time, it applies uniformly across various DLMs and naturally extends to diverse supervision sources. Empirically, TTA improves controllability and fluency: on sentiment control, it yields more than 20 percent higher accuracy and nearly halves perplexity using less than one fifth the steps; in detoxification, it lowers maximum toxicity (12.2 versus 14.5) and perplexity (26.0 versus 32.0). Together, these results demonstrate that softened ordering via timestep allocation is the critical lever for mitigating update forgetting and achieving stable and controllable diffusion text generation.
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