Stochastic Recursive Gradient Descent Ascent for Stochastic
Nonconvex-Strongly-Concave Minimax Problems
- URL: http://arxiv.org/abs/2001.03724v2
- Date: Fri, 23 Oct 2020 09:37:38 GMT
- Title: Stochastic Recursive Gradient Descent Ascent for Stochastic
Nonconvex-Strongly-Concave Minimax Problems
- Authors: Luo Luo, Haishan Ye, Zhichao Huang, Tong Zhang
- Abstract summary: In this paper, we propose a novel method called RecurEnti Ascent (SREDA), which estimates more efficiently using variance.
This method achieves the best known for this problem.
- Score: 36.645753881826955
- License: http://creativecommons.org/publicdomain/zero/1.0/
- Abstract: We consider nonconvex-concave minimax optimization problems of the form
$\min_{\bf x}\max_{\bf y\in{\mathcal Y}} f({\bf x},{\bf y})$, where $f$ is
strongly-concave in $\bf y$ but possibly nonconvex in $\bf x$ and ${\mathcal
Y}$ is a convex and compact set. We focus on the stochastic setting, where we
can only access an unbiased stochastic gradient estimate of $f$ at each
iteration. This formulation includes many machine learning applications as
special cases such as robust optimization and adversary training. We are
interested in finding an ${\mathcal O}(\varepsilon)$-stationary point of the
function $\Phi(\cdot)=\max_{\bf y\in{\mathcal Y}} f(\cdot, {\bf y})$. The most
popular algorithm to solve this problem is stochastic gradient decent ascent,
which requires $\mathcal O(\kappa^3\varepsilon^{-4})$ stochastic gradient
evaluations, where $\kappa$ is the condition number. In this paper, we propose
a novel method called Stochastic Recursive gradiEnt Descent Ascent (SREDA),
which estimates gradients more efficiently using variance reduction. This
method achieves the best known stochastic gradient complexity of ${\mathcal
O}(\kappa^3\varepsilon^{-3})$, and its dependency on $\varepsilon$ is optimal
for this problem.
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