arXiv Computation and Language

Understanding Target Probability Reuse in Speculative Decoding

arXiv Computation and Language
Aug 28

TreeGraft: Adaptive Multi-Drafter Grafting for Tree-Based Speculative Decoding

TreeGraft introduces a multi-drafter framework that combines drafters of varying costs to build a shared draft tree for tree-based speculative decoding. The stronger drafter rescues and rescoring candidates from the weaker drafter, while a lightweight scheduler decides when to invoke the stronger drafter to manage cost. Experiments on 10 model pairs and 6 benchmarks show TreeGraft improves over the best single-drafter strategy by an average of 15.1% and up to 26.6%.

By Jiaming Fan, Daming Cao, Canchen Huang, Jiale Fu, Jin Zhang, Junjie Gao, Kai Yang, Xiangzhong Luo, Xu Yang
Hugging Face Trending Papers
Aug 13

DARTree: Speculative Diffusion Decoding with Autoregressive Draft Trees

Speculative decoding losslessly accelerates autoregressive language models by verifying multiple draft tokens in parallel. Diffusion-based drafters further reduce proposal latency by predicting an entire token block in parallel, but their position-wise distributions are marginal rather than conditioned on tokens selected along each draft path.

arXiv AI
Oct 9

Where Draft Trees Lose Target Mass: Exit-Guided Speculative Decoding

The paper introduces Tree Exit Verification (TEV), an exact, level‑parallel speculative decoding method that uses a single exit‑node decision and a bonus‑token decision to verify draft continuations. By deriving a canonical exit law, the authors show that TEV achieves the same acceptance as optimal verifiers while reducing verifier‑stage latency by 15%. They also propose Exit‑Guided Draft‑Tree Training (ExitTrain), which improves draft trees and increases average output‑block length by 13%, leading to a 14% end‑to‑end speedup over DDTree across dialogue, code, and mathematical reasoning tasks.

By Shijing Hu, Xuancheng Ren, Zhihui Lu, Pan Zhou
arXiv Machine Learning
Oct 3

CAST: Cost-Aware Speculative Trees from One-Pass Block Drafters

CAST (Cost‑Aware Speculative Trees) is a method that improves speculative decoding for large language models by packing multiple drafted token candidates into a tree and verifying the entire tree in a single target‑model pass, rather than only the top‑scoring chain. The tree width is adaptively chosen based on a latency measurement, ensuring that each added candidate’s expected gain outweighs its verification cost. Experiments across five domains, three GPU generations, and two model families show that CAST can be up to 43 % faster than the standard chain, while preserving the target model’s output distribution under both greedy and sampled decoding.

By Jungseob Lee, Sugyeong Eo