REFOCUS: Training-Free Attention Sparsification via Uniform-Reference Filtering

Fengyuan Fan, Rena Wei Gao, Yanbei Jiang


Abstract
Dense softmax attention assigns non-zero probability mass to many task-irrelevant keys, which can dilute useful signals in the attention output. We present REFOCUS, a training-free and plug-and-play inference-time sparsification method that keeps attention entries above a row-wise, context-length-aware threshold and renormalizes the remaining weights. This design is stable, simple to deploy, and requires no model retraining. REFOCUS is integrated in HuggingFace via attn_implementation="refocus" without model-code modification. On Qwen3-4B under 0-shot greedy decoding, REFOCUS matches or outperforms dense eager attention on full-test GSM8K, HumanEval, WinoGrande, and AQuA-RAT, and improves RULER-4k by +0.52 percentage points overall, including +3.20 points on aggregation tasks. These results indicate that a single row-wise threshold can remove diffuse long-tail attention while preserving or improving accuracy.
Anthology ID:
2026.emnlp-main.2668
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, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
60717–60730
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2668/
DOI:
Bibkey:
Cite (ACL):
Fengyuan Fan, Rena Wei Gao, and Yanbei Jiang. 2026. REFOCUS: Training-Free Attention Sparsification via Uniform-Reference Filtering. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 60717–60730, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
REFOCUS: Training-Free Attention Sparsification via Uniform-Reference Filtering (Fan et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2668.pdf