扩散模型推理加速有了新解法——块验证让草稿接受率更高，做生成式 AI 推理优化的团队可以直接参考 Free Drafter 的无训练方案，实测有 6.3% 的提速收益。
该论文提出了一种针对扩散模型的高效推测采样方案，将大语言模型中的块验证技术适配到连续扩散空间，显著提高了草稿的接受率。现有方法在连续空间中采样残差分布时计算效率低，而新方案通过块验证实现了更高效的并行验证。作者还形式化了 Free Drafter——一种无需训练的启发式自推测草稿生成器。实验表明，Free Drafter 在现有推测方法基础上实现了最高 6.3% 的加速，且几乎无额外开销。这项工作为扩散模型的推理加速提供了新思路，尤其适用于需要快速生成高质量样本的场景。
Accelerating Speculative Diffusions via Block Verification
Speculative decoding speeds up LLM inference by using a draft model to generate tokens, with an acceptance-rejection scheme that ensures that the output matches the target distribution. Adapting this to continuous diffusions is difficult because speculative sampling requires drawing from a residual distribution. While straightforward in discrete spaces, efficiently sampling this residual in continuous space is non-trivial. Consequently, existing diffusion adaptations either use computationally inefficient sampling techniques or rely on an alternative scheme. In this work, we introduce a novel scheme that efficiently implements the original speculative sampling mechanism for diffusion models. Our approach offers a critical advantage over current methods: it enables us to adapt block verification from LLMs to diffusions -- which provably improves the acceptance rate of drafts. Furthermore, we formalize and analyze the Free Drafter, a heuristic self-speculative drafter for diffusions that requires no training. By enabling block verification, our Free Drafter yields up to a 6.3% speedup over existing speculative methods with no additional training and negligible overhead beyond the existing parallel verification pass.