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arXiv 2602.08901cs.LG
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GSS:门控子空间定向用于LLM中的选择性记忆抑制

Mitigating Memorization Where It Happens

University of British Columbia;Vector Institute;Independent Researcher

Xuanqi Zhang, Haoyang Shang, Xiaoxiao Li

AI总结:

GSS通过门控子空间定向方法,有效缓解LLM中的选择性记忆问题,比优化方法节省大量计算资源并提升性能。

摘要:

大型语言模型(LLMs)可以逐字记忆和复述训练序列——这种倾向会削弱泛化能力和隐私。现有缓解方法对干预进行统一应用,导致大多数正常泛化的token性能下降。我们实证表明,记忆是稀疏的、间歇的且token条件的,这表明有效的缓解需要基于上下文的干预而非静态参数修改。为此,我们提出了一种新颖且有效的选择性记忆缓解方法——门控子空间定向(GSS),它将干预分解为探测(检测与记忆相关的激活)和定向(仅在探测超过阈值时应用针对性修正)。最优探测-定向对源自基于最优子空间定向的原理性优化框架。在四个基准测试中,GSS在要求比基于优化的替代方法少100-1000倍计算的情况下,匹配或超越了最先进的记忆减少性能。此外,我们还提供了关于神经表示中记忆几何的新理论见解。

英文摘要:

Large language models (LLMs) can memorize and reproduce training sequences verbatim, raising privacy and copyright concerns. Existing mitigation methods apply interventions uniformly, often degrading predictions at the many positions unrelated to verbatim recall. We study a token-level log-likelihood ratio between a target model and a domain-competent reference with lower exposure to the evaluated sequences. Exposure-controlled experiments support its use for localizing positions associated with sequence-level verbatim recall. Across evaluated settings, a minority of positions carries a disproportionate share of the positive signal, motivating selective activation correction. From a first-order surrogate of the memorization-reduction objective, we derive a probe-steer framework, which decomposes intervention into a probe that flags high-signal activations and a steer that applies a correction only when the probe exceeds a threshold. We propose Gated Subspace Steering (GSS) as its practical instantiation: under a background normalization constraint, the probe-steer pairs that are optimal for this surrogate follow in closed form from the leading singular vectors of a whitened gradient-weighted activation matrix. Across four benchmarks, GSS achieves memorization suppression comparable to strong baselines, with favorable utility trade-offs in several settings, while requiring 10-100$\times$ less compute than optimization-based alternatives. Code is available at https://github.com/ubc-tea/Mitigating-Memorization-Where-It-Happens.

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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