A Unified Per-Token Gating Family for On-Policy Distillation: FKL/RKL Mixing with Multi-Channel and Bias Coefficients

Suwan Wu, Yumeng Lin, Pengcheng Yuan, Xiaolong Jiang


Abstract
Per-token gating of forward/reverse KL losses has emerged as a key technique for on-policy distillation (OPD), but existing methods such as EOPD (Agarwal et al., 2024) and ToDi (Jung et al., 2025) each commit to a single gating signal and a single direction. It is unclear which signal works best for a given task, or whether gating helps consistently. We introduce a unified analysis framework: a four-coefficient parameterization 𝜎(a, ht + b, ux + c + d, gapt) in which EOPD and ToDi appear as 1D restrictions, exposing multi-channel composition and an explicit bias term as additional structural degrees of freedom. On TweetEval emotion and hate, our framework improves over the matched-magnitude 1D restrictions in 33 of 36 comparable configurations (91.7%). A 26-configuration mean-match isolation experiment shows that dynamic OPD outperforms effective-KL-matched static baselines in 19 of 26 cases, with no configuration falling below the -1𝜎 noise band relative to its matched static counterpart. The optimal (a,b,c,d) is task-conditional: emotion favors entropy, hate favors prompt-level uncertainty.
Anthology ID:
2026.findings-emnlp.1082
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:
22921–22933
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1082/
DOI:
Bibkey:
Cite (ACL):
Suwan Wu, Yumeng Lin, Pengcheng Yuan, and Xiaolong Jiang. 2026. A Unified Per-Token Gating Family for On-Policy Distillation: FKL/RKL Mixing with Multi-Channel and Bias Coefficients. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 22921–22933, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
A Unified Per-Token Gating Family for On-Policy Distillation: FKL/RKL Mixing with Multi-Channel and Bias Coefficients (Wu et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.1082.pdf