DarterSD: Dynamic Token-Weighted Distillation for High-Efficient Speculative Decoding

Zhaoning Zhang, Xu Baizhou, Libo Zhang, Yi Chen, Zhiliang Tian, Zhen Huang, Dongsheng Li


Abstract
Speculative decoding accelerates autoregressive LLM generation with a lightweight draft model, yet existing distillation methods treat all historical tokens equally despite their divergent contributions to next-token prediction. We discover that attention in draft models is extremely concentrated: the top-3 historical tokens capture 80% of attention weight, while over 90% of tokens contribute negligibly. This uniform training paradigm forces the draft model to learn from noisy, low-importance tokens, diluting the learning signal from informative positions and limiting the alignment between draft and target distributions. To address this, we propose DarterSD, a dynamic token-weighted distillation framework for efficient speculative decoding. DarterSD employs a learnable sigmoid gate in self-attention to compute per-token importance scores, and designs a multi-objective distillation loss comprising distribution alignment, logit matching, and gate regularization to focus training on high-informative tokens. We further introduce a lightweight Boolean-mask denoising strategy at inference to suppress contextual noise, without modifying the target model’s verification pipeline. Experiments show DarterSD delivers a lossless speedup up to 5.52x , outperforming EAGLE3 (4.67x), and boosts the average accepted token length by 12.9%.
Anthology ID:
2026.findings-emnlp.749
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:
15773–15788
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.749/
DOI:
10.18653/2026.findings-emnlp.749
Bibkey:
Cite (ACL):
Zhaoning Zhang, Xu Baizhou, Libo Zhang, Yi Chen, Zhiliang Tian, Zhen Huang, and Dongsheng Li. 2026. DarterSD: Dynamic Token-Weighted Distillation for High-Efficient Speculative Decoding. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 15773–15788, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
DarterSD: Dynamic Token-Weighted Distillation for High-Efficient Speculative Decoding (Zhang et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.749.pdf