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OPT-Tree: Speculative Decoding with Adaptive Draft Tree Structure

delete2025-02-28
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OA
AI
J
Jikai Wang
Y
Yi Su
李俊涛 cover
李俊涛 (Juntao Li) *
Z
Zi Ye
X
Xinyu Duan
Z
Zhefeng Wang
张民 (Min Zhang)
DOI:10.1162/tacl_a_00735delete
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Abstract

Abstract

En 中文
Autoregressive language models demonstrate excellent performance in various scenarios. However, the inference efficiency is limited by its one-step-one-word generation mode, which has become a pressing problem recently as the models become increasingly larger. Speculative decoding employs a draft and then verifymechanism to allow multiple tokens to be generated in one step, realizing lossless acceleration. Existing methods mainly adopt fixed heuristic draft structures, which do not adapt to different situations to maximize the acceptance length during verification. To alleviate this dilemma, we propose OPT-Tree, an algorithm to construct adaptive and scalable draft trees, which can be applied to any autoregressive draft model. It searches the optimal tree structure that maximizes the mathematical expectation of the acceptance length in each decoding step. Experimental results reveal that OPT-Tree outperforms the existing draft structures and achieves a speed-up ratio of up to 3.2 compared with autoregressive decoding. If the draft model is powerful enough and the node budget is sufficient, it can generate more than ten tokens in a single step.

Journal

T
Transactions of the Association for Computational Linguistics
IF:
6.9
Papers:
486
Citations:
5.7K

Organization

S
Soochow Univ
Scholars:
5.5K
Papers: 1.9K
Citations: 689
H
huawei cloud
Scholars:
9
Papers: 4
Citations: 0
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