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arXiv 2602.13151cs.LGcs.CL
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通过低秩适应实现抗量化的大语言模型反学习

Quantization-Robust LLM Unlearning via Low-Rank Adaptation

Kunumi Institute, Brazil(Kunumi研究所,巴西)

João Vitor Boer Abitante, Joana Meneguzzo Pasquali, Luan Fonseca Garcia, Ewerton de Oliveira, Thomas da Silva Paula, Rodrigo C. Barros, Lucas S. Kupssinskü

AI总结:

本文提出LoRA方法,通过冻结基础模型并集中反学习到可训练适配器中,提升4位量化下的模型性能,同时减少隐私泄露,适用于需要量化部署的场景。

摘要:

大型语言模型(LLM)反学习旨在从训练模型中移除特定知识,但实际部署通常需要训练后量化(PTQ)以提高推理效率。然而,激进的低比特PTQ会掩盖反学习更新,导致量化模型恢复到反学习前的行为。我们证明标准全参数微调通常诱导的参数变化太小,无法在4位量化下存活。我们提出通过低秩适应(LoRA)实现抗量化反学习:冻结基础模型并将反学习集中于可训练适配器中,以在量化后保留有效更新。在Llama-2-7B上使用MUSE数据集(BOOKS和NEWS)评估,LoRA在4位量化下提升性能达7.93个百分点(NPO+GDR在BOOKS上从50.17提升到58.10),并在NEWS上通过GA+GDR实现4.76个百分点的提升。LoRA还显著减少4位PTQ下的隐私泄露,例如在BOOKS上通过GA+KLR,PrivLeak从-25.68降至-5.86(接近理想值0),同时保持强遗忘(VerMem和KnowMem接近0)。因此,使用LoRA进行机器反学习对需要量化部署的场景是有益的。

英文摘要:

Large Language Model (LLM) unlearning aims to remove targeted knowledge from a trained model, but practical deployments often require post-training quantization (PTQ) for efficient inference. However, aggressive low-bit PTQ can mask unlearning updates, causing quantized models to revert to pre-unlearning behavior. We show that standard full-parameter fine-tuning often induces parameter changes that are too small to survive 4-bit quantization. We propose quantization-robust unlearning via low-rank adaptation (LoRA): we freeze the base model and concentrate unlearning into trainable adapters so that the effective update is preserved after quantization. On Llama-2-7B evaluated with MUSE dataset (BOOKS and NEWS), LoRA improves 4-bit utility by up to 7.93 points (NPO+GDR on BOOKS: 50.17 to 58.10) and yields higher 4-bit utility on NEWS for GA+GDR (40.06 to 44.82, increase of 4.76). LoRA also substantially reduces privacy leakage under 4-bit PTQ, e.g., for GA+KLR on BOOKS, PrivLeak moves from -25.68 to -5.86 (closer to ideal 0), while maintaining strong forgetting (VerMem and KnowMem near 0). Thus, using LoRA for Machine Unlearning is beneficial for scenarios where quantization is necessary for model deployment.

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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