论文标题

在差异私有优化中,更快的收敛速度与固定点

Faster Rates of Convergence to Stationary Points in Differentially Private Optimization

论文作者

Arora, Raman, Bassily, Raef, González, Tomás, Guzmán, Cristóbal, Menart, Michael, Ullah, Enayat

论文摘要

我们研究了在有限的sum和随机设置中,在$(\ varepsilon,δ)$差异隐私(dp)下近似固定点的固定点和平滑函数的问题。一个点$ \ wideHat {w} $称为$ f:\ mathbb {r}^d \ rightArrow \ mathbb {r} $的$α$ - 定位点。我们提供了一种新的有效算法,该算法找到了$ \ tilde {o} \ big(\ big [\ frac {\ sqrt {\ sqrt {d}} {n \ varepsilon} \ big]^{2/3} {2/3} \ big)$ - n $ n $ s same s same s same s same by s same。这可以提高$ \ tilde {o} \ big(\ big [\ frac {\ sqrt {d}}} {n \ varepsilon} \ big]^{1/2} \ big)$的最佳最佳费率。我们还提供了一种新的结构,可以改善随机优化环境中的现有利率,目标是找到人口风险的近似固定点。我们的构造找到了一个$ \ tilde {o} \ big(\ frac {1} {n^{1/3}}} + \ big [\ frac {\ sqrt {\ sqrt {d}} {n \ varepsilon} {n \ varepsilon} \ big]此外,在凸度的额外假设下,我们完全表征了寻找人口风险的固定点的样本复杂性(最终到聚log因素),并表明人口平稳性的最佳速率为$ \ tilde θ\ big(\ frac {1} {\ sqrt {n}}}+\ frac {\ sqrt {d}}} {n \ varepsilon} \ big)$。最后,我们表明我们的方法可用于提供独立的尺寸的速率$ o \ big(\ frac {1} {\ sqrt {n}}}+\ min \ big(\ big [\ frac {\ sqrt {rank rank {strank}}} {n \ v arepsilon} \ big]^{2/3},\ frac {1} {(n \ varepsilon)^{2/5}}}} \ big)\ big)$关于广义线性模型(GLM)的人口平稳性,其中$等级$是设计矩阵的等级,它以先前最佳的速率提高了。

We study the problem of approximating stationary points of Lipschitz and smooth functions under $(\varepsilon,δ)$-differential privacy (DP) in both the finite-sum and stochastic settings. A point $\widehat{w}$ is called an $α$-stationary point of a function $F:\mathbb{R}^d\rightarrow\mathbb{R}$ if $\|\nabla F(\widehat{w})\|\leq α$. We provide a new efficient algorithm that finds an $\tilde{O}\big(\big[\frac{\sqrt{d}}{n\varepsilon}\big]^{2/3}\big)$-stationary point in the finite-sum setting, where $n$ is the number of samples. This improves on the previous best rate of $\tilde{O}\big(\big[\frac{\sqrt{d}}{n\varepsilon}\big]^{1/2}\big)$. We also give a new construction that improves over the existing rates in the stochastic optimization setting, where the goal is to find approximate stationary points of the population risk. Our construction finds a $\tilde{O}\big(\frac{1}{n^{1/3}} + \big[\frac{\sqrt{d}}{n\varepsilon}\big]^{1/2}\big)$-stationary point of the population risk in time linear in $n$. Furthermore, under the additional assumption of convexity, we completely characterize the sample complexity of finding stationary points of the population risk (up to polylog factors) and show that the optimal rate on population stationarity is $\tilde Θ\big(\frac{1}{\sqrt{n}}+\frac{\sqrt{d}}{n\varepsilon}\big)$. Finally, we show that our methods can be used to provide dimension-independent rates of $O\big(\frac{1}{\sqrt{n}}+\min\big(\big[\frac{\sqrt{rank}}{n\varepsilon}\big]^{2/3},\frac{1}{(n\varepsilon)^{2/5}}\big)\big)$ on population stationarity for Generalized Linear Models (GLM), where $rank$ is the rank of the design matrix, which improves upon the previous best known rate.

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