RADAR: Accelerate Large Language Model Inference with RL-Based Dynamic Draft Trees

Junjie Ma, Jinlong Li, Jiajun Luo


Abstract
Inference with modern Large Language Models (LLMs) is expensive and slow, and speculative sampling has emerged as an effective solution to this problem. However, the number of calls to the draft model for generating candidate tokens in speculative sampling is a preset hyperparameter, lacking flexibility. To generate and utilize the candidate tokens more effectively, we propose RADAR, a novel speculative sampling method with RL-based dynamic draft trees. RADAR formulates the draft tree generation process as a Markov Decision Process (MDP) and employs offline reinforcement learning to train a prediction model, which enables real-time decisions on calls to the draft model, reducing redundant computations and further accelerating inference. Evaluations across three LLMs and four tasks show that RADAR achieves a speedup of 3.17x-4.82x over the auto-regressive decoding baseline.
Anthology ID:
2026.findings-emnlp.1610
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
34289–34301
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1610/
DOI:
Bibkey:
Cite (ACL):
Junjie Ma, Jinlong Li, and Jiajun Luo. 2026. RADAR: Accelerate Large Language Model Inference with RL-Based Dynamic Draft Trees. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 34289–34301, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
RADAR: Accelerate Large Language Model Inference with RL-Based Dynamic Draft Trees (Ma et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1610.pdf