arXiv:2602.14938cs.LGmath.OC2026-02

提出首个直接使用遗忘数据梯度的无偏机器遗忘算法,兼顾理论保证与实际效果。

Variance-Reduced $(\varepsilon,δ)-$Unlearning using Forget Set Gradients

  • 直接在更新中使用遗忘样本梯度,提升优化效率。
  • 理论证明误差收敛速度优于现有方法,低误差下优势更明显。
  • 适合需要严格数据删除保障的高安全场景应用。

在机器遗忘中,(ε,δ)-遗忘是一种提供训练数据子集(遗忘集)从模型中移除有效性形式保证的流行框架。对于强凸目标函数,现有的一阶方法可实现(ε,δ)-遗忘,但仅将遗忘集用于调节注入噪声,从未将其作为直接优化信号。相反,高效的启发式方法常利用遗忘样本(如通过梯度上升),但缺乏正式的遗忘保证。本文提出方差减少遗忘(VRU)算法,据我们所知,它是首个在更新规则中直接包含遗忘集梯度的一阶算法,同时可证明满足(ε,δ)-遗忘。我们建立了VRU的收敛性,并证明引入遗忘集可显著改善收敛率,即在达到的误差上具有更优依赖关系,优于现有的一阶(ε,δ)-遗忘方法。此外,我们在低误差情形下证明,VRU渐近优于任何忽略遗忘集的一阶方法。实验验证了理论结果,显示其在性能上持续超越最先进的认证遗忘方法以及显式利用遗忘集的启发式基线。

原文摘要 · Abstract (English)

In machine unlearning, $(\varepsilon,δ)-$unlearning is a popular framework that provides formal guarantees on the effectiveness of the removal of a subset of training data, the forget set, from a trained model. For strongly convex objectives, existing first-order methods achieve $(\varepsilon,δ)-$unlearning, but they only use the forget set to calibrate injected noise, never as a direct optimization signal. In contrast, efficient empirical heuristics often exploit the forget samples (e.g., via gradient ascent) but come with no formal unlearning guarantees. We bridge this gap by presenting the Variance-Reduced Unlearning (VRU) algorithm. To the best of our knowledge, VRU is the first first-order algorithm that directly includes forget set gradients in its update rule, while provably satisfying ($(\varepsilon,δ)-$unlearning. We establish the convergence of VRU and show that incorporating the forget set yields strictly improved rates, i.e. a better dependence on the achieved error compared to existing first-order $(\varepsilon,δ)-$unlearning methods. Moreover, we prove that, in a low-error regime, VRU asymptotically outperforms any first-order method that ignores the forget set.Experiments corroborate our theory, showing consistent gains over both state-of-the-art certified unlearning methods and over empirical baselines that explicitly leverage the forget set.

机器遗忘优化算法理论保证

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