通过更优的并行解码策略,让扩散语言模型推理快37%且不丢精度。
Fast-dLLM++: Fréchet Profile Decoding for Faster Diffusion LLM Inference

- 基于置信度分布动态选择并行提交的词元组合,突破原有最弱词元限制。
- 在相同准确率下,推理吞吐量最高提升37%,实测效果显著优于原方法。
- 无需训练、可直接替换现有系统,适合追求高效推理的开发者使用。
扩散语言模型有望实现并行词元生成,但推理速度受限于如何安全地批量确认被掩码的词元。Fast-dLLM通过键值缓存与置信度引导的并行解码缓解此问题,但其理论依赖于高置信度同质假设,实质上将候选集简化为最弱词元。我们指出这会浪费性能,因实际解码中置信度分布具有异质性。为此提出 extbf{Fast-dLLM++},一种无训练扩展,引入 extit{Fréchet 置信度轮廓解码}:从完整排序的置信度分布中选取并行提交集,而非仅取最弱置信度。该规则是 Fast-dLLM 因子选择器的异质性推广,在等置信度时退化为原规则,并在不均置信度下带来可证明的 extit{异质性收益}。Fast-dLLM++ 不改变模型、扩散过程和缓存实现,可作为即插即用的替代方案。在 GSM8K、MATH、HumanEval 与 MBPP 上使用 LLaDA-8B 模型的实验表明,理论优势直接转化为实证增益:轮廓感知选择能挖掘传统最弱词元规则遗漏的安全并行性,使准确率-吞吐率前沿得到提升,在相近准确率下最高达37%吞吐量增长。代码已开源:https://github.com/Ringo-Star/FastdLLM_plusplus。
原文摘要 · Abstract (English)
Diffusion large language models promise parallel token generation, yet inference remains bottlenecked by deciding which masked tokens can be safely committed together. Fast-dLLM addressed this with KV caching and confidence-guided parallel decoding, but its decoding theory uses a homogeneous high-confidence assumption that effectively reduces each candidate set to its weakest selected token. We argue that this leaves speed on the table because real decoding steps exhibit heterogeneous confidence profiles. We propose \textbf{Fast-dLLM++}, a training-free extension that introduces \emph{Fréchet profile decoding}: selecting parallel commit sets from the full sorted confidence profile rather than a single worst-case confidence. The resulting rule is a heterogeneous-confidence generalization of Fast-dLLM's factor selector and it recovers the previous rule exactly in the equal-confidence case and adds a provable \emph{heterogeneity bonus} when the selected tokens have uneven confidences. Fast-dLLM++ leaves the model, diffusion process, and cache implementation entirely unchanged, making it a drop-in replacement for existing Fast-dLLM decoding. Experiments on GSM8K, MATH, HumanEval, and MBPP with the LLaDA-8B model show that the theoretical improvement translates directly into empirical gains: profile-aware selection improves the accuracy--throughput frontier by exploiting safe parallelism that weakest-token rules miss, achieving up to 37\% higher throughput at comparable accuracy. Our code release is at https://github.com/Ringo-Star/FastdLLM_plusplus.
Thank you to arXiv for use of its open access interoperability. PaperDance 不是 arXiv 官方产品;中文卡片由大模型生成,请以原文为准。