High probability guarantees for stochastic convex optimization
Damek Davis, Dmitriy Drusvyatskiy
Subject areas: Stochastic optimization, Computational complexity, Convex optimization, Excess risk bounds and generalization error bounds
Presented in: Session 1B, Session 1D
[Zoom link for poster in Session 1B], [Zoom link for poster in Session 1D]
Abstract:
Standard results in stochastic convex optimization bound the number of samples that an algorithm needs to generate a point with small function value in expectation. More nuanced high probability guarantees are rare, and typically either rely on ``light-tail'' noise assumptions or exhibit worse sample complexity. In this work, we show that a wide class of stochastic optimization algorithms for strongly convex problems can be augmented with high confidence bounds at an overhead cost that is only logarithmic in the confidence level and polylogarithmic in the condition number. The procedure we propose, called proxBoost, is elementary and builds on two well-known ingredients: robust distance estimation and the proximal point method. We discuss consequences for both streaming (online) algorithms and offline algorithms based on empirical risk minimization.