Less Random, More Incoherent: Greedy Hadamard Alignment for LLM Quantization

Yun Ye, Zhaoqi Wu, Xueshu Wang, Cong Zhang, Zhu Yongbo, Zhonghua Sun, Beryl XU


Abstract
Hadamard preprocessing is widely used in large language model (LLM) quantization to reduce activation coherence and suppress peaks. Existing methods typically rely on random sign flips before the Hadamard transform, which do not use information from the target data distribution. We propose Greedy Hadamard Alignment (GHA), a simple training-free method to build a signed-permutation preconditioner from calibration data. GHA uses a pooled representative activation, a greedy search over flat targets, and an efficient alignment step that is analytically optimal once the target is fixed. We also study when one shared GHA preconditioner can transfer across LLM activations. GHA works best when activations are directionally aligned and stable across calibration sources. Overall, GHA improves post-quantization model quality over randomized Hadamard baselines, with the strongest gains in KV-cache quantization, more moderate gains for hidden states, and little compute overhead during inference.
Anthology ID:
2026.aacl-long.70
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1526–1540
Language:
URL:
https://aclanthology.org/2026.aacl-long.70/
DOI:
Bibkey:
Cite (ACL):
Yun Ye, Zhaoqi Wu, Xueshu Wang, Cong Zhang, Zhu Yongbo, Zhonghua Sun, and Beryl XU. 2026. Less Random, More Incoherent: Greedy Hadamard Alignment for LLM Quantization. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 1526–1540, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Less Random, More Incoherent: Greedy Hadamard Alignment for LLM Quantization (Ye et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.70.pdf