arXiv:2502.14772cs.DScs.LG2025-02ICML被引 5

提出首个高效算法,可在高维下容忍恒定比例异常值,准确估计均值。

Efficient Multivariate Robust Mean Estimation Under Mean-Shift Contamination

  • 设计新算法,通过筛选与目标均值一致的点来抵抗任意异常均值污染。
  • 在样本量接近理论最优时,以多项式时间收敛至任意精度。
  • 适用于需处理非随机异常数据的机器学习场景,如鲁棒统计与安全建模。

研究在均值偏移污染模型下,对协方差为单位阵的高斯分布进行鲁棒均值估计的算法问题。给定一组 $\mathbb{R}^d$ 中的点,其中每个样本 $x_i$ 以概率 $1-α$ 从 $\mathcal{N}(μ, I)$ 采样($μ$ 为目标均值),以概率 $α$ 从 $\mathcal{N}(z_i, I)$ 采样($z_i$ 未知且可能任意)。此前工作已刻画该任务的信息论极限:与Huber污染不同,均值偏移下可实现一致估计。但现有鲁棒估计器的运行时间在维度上呈指数级。本文首次给出高维鲁棒均值估计的计算高效算法,可容忍常数比例的异常值。算法具有近似最优样本复杂度,运行时间为样本多项式时间,能以任意精度逼近目标均值。本结果推动了对介于完全对抗性与随机噪声之间的自然噪声模型的推断研究。

原文摘要 · Abstract (English)

We study the algorithmic problem of robust mean estimation of an identity covariance Gaussian in the presence of mean-shift contamination. In this contamination model, we are given a set of points in $\mathbb{R}^d$ generated i.i.d. via the following process. For a parameter $α<1/2$, the $i$-th sample $x_i$ is obtained as follows: with probability $1-α$, $x_i$ is drawn from $\mathcal{N}(μ, I)$, where $μ\in \mathbb{R}^d$ is the target mean; and with probability $α$, $x_i$ is drawn from $\mathcal{N}(z_i, I)$, where $z_i$ is unknown and potentially arbitrary. Prior work characterized the information-theoretic limits of this task. Specifically, it was shown that, in contrast to Huber contamination, in the presence of mean-shift contamination consistent estimation is possible. On the other hand, all known robust estimators in the mean-shift model have running times exponential in the dimension. Here we give the first computationally efficient algorithm for high-dimensional robust mean estimation with mean-shift contamination that can tolerate a constant fraction of outliers. In particular, our algorithm has near-optimal sample complexity, runs in sample-polynomial time, and approximates the target mean to any desired accuracy. Conceptually, our result contributes to a growing body of work that studies inference with respect to natural noise models lying in between fully adversarial and random settings.

鲁棒估计高维统计异常检测

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