通过尾部锚点调节信心,提升扩散语言模型的完整生成能力。
When Confidence Misleads: Suffix Anchoring and Anchor-Proximity Confidence Modulation for Diffusion Language Models

- 用尾部锚点引导模型避免过早结束生成
- 在锚点附近动态调节置信度,防止提前解码
- 无需训练,适合高并行推理场景
扩散语言模型通过迭代选择和去噪掩码位置生成文本,位置选择是推理阶段的核心决策。现有无训练方法依赖模型置信度,假设高置信度位置可立即解码。但在全非自回归(fully non-AR)解码中,该假设失效,导致生成不完整,部分源于对结束符(EOT)的过自信。现有方法直接抑制EOT,效果有限或需微调。本文发现,在响应区域末端添加语义极简的后缀锚点,能抑制过早预测EOT,促进完整生成。但锚点虽无实质上下文,却使邻近位置置信度骤升,导致过早解码。为此提出后缀锚定置信度调节(Suffix-Anchored Confidence Modulation),一种无需训练的方法,在锚点附近实现进度相关的置信度调节。在纯文本推理、视觉-语言推理和代码生成等多个基准上,优于多种全非自回归与半自回归基线。尤其在高度并行解码下提升显著,表明改进全非自回归范式优于分块半自回归范式。
原文摘要 · Abstract (English)
Diffusion language models generate text by iteratively selecting and denoising masked positions, making position selection a central inference-time decision. Most training-free methods rely on model confidence, assuming that high-confidence positions are ready to be decoded. However, this assumption can fail in fully non-autoregressive (fully non-AR) decoding, where selection spans the entire masked response sequence. This can cause incomplete generation, partly due to EOT overconfidence. Existing remedies directly suppress EOT tokens, but provide limited gains or require additional fine-tuning. We show that placing even a semantically minimal suffix anchor near the end of the response region discourages premature EOT prediction and promotes complete generation. However, despite providing little supporting context, the anchor makes nearby positions highly confident and causes them to be decoded too early. We therefore propose Suffix-Anchored Confidence Modulation, a simple training-free method that uses suffix anchoring with progress-dependent confidence modulation near the anchor. Across text-only reasoning, vision-language reasoning, and code-generation benchmarks, our method outperforms diverse fully non-AR and semi-AR baselines. It also achieves particularly large gains under highly parallel decoding, demonstrating the benefit of improving the fully non-AR regime over block-wise semi-AR regime.
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