arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2602.02001cs.LGcs.AI
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在量化误差重建中平衡秩预算:用于大语言模型的秩预算平衡

Preserve-Then-Quantize: Balancing Rank Budgets for Quantization Error Reconstruction in LLMs

Department of Computer Science, Yonsei University(延世大学计算机科学系);Department of Artificial Intelligence, Yonsei University(延世大学人工智能系)

Yoonjun Cho, Dongjae Jeon, Soeun Kim, Moongyu Jeon, Albert No

AI总结:

本文提出SRR框架,通过在量化前保留激活缩放权重的前k个奇异子空间,仅量化残差,并利用剩余秩r-k进行误差重建,从而在秩约束下平衡量化暴露能量和不可恢复误差,提升PTQ精度。

摘要:

量化误差重建(QER)通过将权重近似为W≈Q+LR,利用秩r的修正来重建量化误差,以减少后训练量化(PTQ)中的精度损失。先前方法将全部秩预算用于误差重建,当W具有内在低秩结构且量化破坏主导方向时效果不佳。本文提出结构残差重建(SRR),是一种秩分配框架,该框架在量化前保留激活缩放权重的前k个奇异子空间,仅量化残差,并利用剩余秩r-k进行误差重建。我们推导出一个理论指导的标准,通过在秩约束下平衡量化暴露能量和不可恢复误差来选择k。我们进一步证明,所得到的Q+LR参数化自然支持量化参数高效微调(QPEFT),并通过沿保留方向的梯度缩放稳定微调。实验表明,在PTQ中,不同模型和量化设置下均实现了一致的困惑度降低,同时在2位QPEFT下,GLUE基准上平均提升了5.9个百分点。项目页面可在https://ai-isl.github.io/srr访问。

英文摘要:

Quantization Error Reconstruction (QER) reduces accuracy loss in Post-Training Quantization (PTQ) by approximating weights as $\mathbf{W} \approx \mathbf{Q} + \mathbf{L}\mathbf{R}$, using a rank-$r$ correction to reconstruct quantization error. Prior methods devote the full rank budget to error reconstruction, which is suboptimal when $\mathbf{W}$ has intrinsic low-rank structure and quantization corrupts dominant directions. We propose Structured Residual Reconstruction (SRR), a rank-allocation framework that preserves the top-$k$ singular subspace of the activation-scaled weight before quantization, quantizes only the residual, and uses the remaining rank $r-k$ for error reconstruction. We derive a theory-guided criterion for selecting $k$ by balancing quantization-exposed energy and unrecoverable error under rank constraints. We further show that resulting $\mathbf{Q} + \mathbf{L}\mathbf{R}$ parameterization naturally supports Quantized Parameter-Efficient Fine-Tuning (QPEFT), and stabilizes fine-tuning via gradient scaling along preserved directions. Experiments demonstrate consistent perplexity reductions across diverse models and quantization settings in PTQ, along with a 5.9 percentage-point average gain on GLUE under 2-bit QPEFT. The project page is available at https://ai-isl.github.io/srr.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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