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arXiv · 2406.19579

Private Zeroth-Order Nonsmooth Nonconvex Optimization

Qinzi Zhang·Hoang Tran·Ashok Cutkosky
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Abstract

We introduce a new zeroth-order algorithm for private stochastic optimization on nonconvex and nonsmooth objectives. Given a dataset of size $M$, our algorithm ensures $(\alpha,\alpha\rho^2/2)$-R\'enyi differential privacy and finds a $(\delta,\epsilon)$-stationary point so long as $M=\tilde\Omega\left(\frac{d}{\delta\epsilon^3} + \frac{d^{3/2}}{\rho\delta\epsilon^2}\right)$. This matches the optimal complexity of its non-private zeroth-order analog. Notably, although the objective is not smooth, we have privacy ``for free'' whenever $\rho \ge \sqrt{d}\epsilon$.

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Qinzi Zhang, Hoang Tran, Ashok Cutkosky. 2024-06-27. Private Zeroth-Order Nonsmooth Nonconvex Optimization. https://arxiv.org/abs/2406.19579

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