Rethinking the Role of Temperature in Large Language Model Distillation

Hoang-Chau Luong, Lingwei Chen


Abstract
Reverse Kullback–Leibler (RKL) divergence is widely favored over forward KL (FKL) in large language models (LLM) distillation, yet this preference is largely based on comparisons that omit the temperature 𝜏, overlooking its central role in softening teacher distributions and improving knowledge transfer. In this work, we revisit temperature in LLM distillation and show that it fundamentally changes the comparison between FKL and RKL. Our analysis reveals an asymmetric effect: temperature substantially enriches FKL with non-dominant token signals, whereas it mainly rescales RKL gradients, causing FKL to benefit much more from 𝜏 scaling than RKL. This asymmetry overturns the standard empirical conclusion: although RKL outperforms FKL at 𝜏=1, FKL consistently surpasses RKL at higher temperatures across instruction-following benchmarks. Moreover, the impact of temperature is not limited to FKL; it improves a broader family of distillation objectives, enabling simple KL-based methods to achieve competitive performance against recent state-of-the-art LLM distillation approaches.
Anthology ID:
2026.emnlp-main.1191
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Junyi Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
27292–27303
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1191/
DOI:
10.18653/2026.emnlp-main.1191
Bibkey:
Cite (ACL):
Hoang-Chau Luong and Lingwei Chen. 2026. Rethinking the Role of Temperature in Large Language Model Distillation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 27292–27303, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Rethinking the Role of Temperature in Large Language Model Distillation (Luong & Chen, EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.1191.pdf