Yggdrasil: Bridging Dynamic Speculation and Static Runtime for Latency-Optimal Tree-Based LLM Decoding

Fuente: arXiv
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Autores principales: Guan, Yue, Yu, Changming, Fang, Shihan, Hu, Weiming, Pan, Zaifeng, Wang, Zheng, Liu, Zihan, Zhou, Yangjie, Ding, Yufei, Guo, Minyi, Leng, Jingwen
Formato: Preprint
Publicado: 2025
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author Guan, Yue
Yu, Changming
Fang, Shihan
Hu, Weiming
Pan, Zaifeng
Wang, Zheng
Liu, Zihan
Zhou, Yangjie
Ding, Yufei
Guo, Minyi
Leng, Jingwen
author_facet Guan, Yue
Yu, Changming
Fang, Shihan
Hu, Weiming
Pan, Zaifeng
Wang, Zheng
Liu, Zihan
Zhou, Yangjie
Ding, Yufei
Guo, Minyi
Leng, Jingwen
contents Speculative decoding improves LLM inference by generating and verifying multiple tokens in parallel, but existing systems suffer from suboptimal performance due to a mismatch between dynamic speculation and static runtime assumptions. We present Yggdrasil, a co-designed system that enables latency-optimal speculative decoding through context-aware tree drafting and compiler-friendly execution. Yggdrasil introduces an equal-growth tree structure for static graph compatibility, a latency-aware optimization objective for draft selection, and stage-based scheduling to reduce overhead. Yggdrasil supports unmodified LLMs and achieves up to $3.98\times$ speedup over state-of-the-art baselines across multiple hardware setups.
format Preprint
id arxiv_https___arxiv_org_abs_2512_23858
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Yggdrasil: Bridging Dynamic Speculation and Static Runtime for Latency-Optimal Tree-Based LLM Decoding
Guan, Yue
Yu, Changming
Fang, Shihan
Hu, Weiming
Pan, Zaifeng
Wang, Zheng
Liu, Zihan
Zhou, Yangjie
Ding, Yufei
Guo, Minyi
Leng, Jingwen
Machine Learning
Programming Languages
Speculative decoding improves LLM inference by generating and verifying multiple tokens in parallel, but existing systems suffer from suboptimal performance due to a mismatch between dynamic speculation and static runtime assumptions. We present Yggdrasil, a co-designed system that enables latency-optimal speculative decoding through context-aware tree drafting and compiler-friendly execution. Yggdrasil introduces an equal-growth tree structure for static graph compatibility, a latency-aware optimization objective for draft selection, and stage-based scheduling to reduce overhead. Yggdrasil supports unmodified LLMs and achieves up to $3.98\times$ speedup over state-of-the-art baselines across multiple hardware setups.
title Yggdrasil: Bridging Dynamic Speculation and Static Runtime for Latency-Optimal Tree-Based LLM Decoding
topic Machine Learning
Programming Languages
url https://arxiv.org/abs/2512.23858