Sparsity in Linear Attention Models: Bregman Testing Time Learning

Wenqi Zeng, YuAng Chen, Yuxuan Chen, Chumin Sun, Weihuang Wen, Yichuan Liu, Li Zhou, Tian Wang, Fan Zhang, Yuan Yao, Jie Sun


Abstract
Linear attention architectures enable efficient long-context modeling by compressing sequence history into a fixed-size memory state. However, dense key value updates can overload the state as the context grows, causing memory collisions and degraded retrieval. Existing methods rely on memory decay, rank reduction, or heuristic routing to reduce interference, but they largely preserve dense online updates and do not explicitly control the structural complexity of memory. We introduce BregNet, a linear sequence architecture that formulates associative memory updates as a regularized online regression problem. Based on Linearized Bregman Iteration (LBI), BregNet decouples memory into a continuous dual accumulator and a structurally sparse primal state. The dual state records incoming information, while the sparse primal state keeps only important associations and removes noise through soft shrinkage. Experiments show that BregNet matches strong linear baselines in language modeling even with high memory sparsity. In this way, BregNet prevents the memory state from being overloaded by dense and interfering updates.
Anthology ID:
2026.findings-emnlp.2246
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
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
48075–48094
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URL:
https://aclanthology.org/2026.findings-emnlp.2246/
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Cite (ACL):
Wenqi Zeng, YuAng Chen, Yuxuan Chen, Chumin Sun, Weihuang Wen, Yichuan Liu, Li Zhou, Tian Wang, Fan Zhang, Yuan Yao, and Jie Sun. 2026. Sparsity in Linear Attention Models: Bregman Testing Time Learning. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 48075–48094, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Sparsity in Linear Attention Models: Bregman Testing Time Learning (Zeng et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.2246.pdf