Exponential Concentration in Stochastic Approximation

Fuente: arXiv
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Autori principali: Law, Kody, Walton, Neil, Yang, Shangda
Natura: Preprint
Pubblicazione: 2022
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author Law, Kody
Walton, Neil
Yang, Shangda
author_facet Law, Kody
Walton, Neil
Yang, Shangda
contents We analyze the behavior of stochastic approximation algorithms where iterates, in expectation, progress towards an objective at each step. When progress is proportional to the step size of the algorithm, we prove exponential concentration bounds. These tail-bounds contrast asymptotic normality results, which are more frequently associated with stochastic approximation. The methods that we develop rely on a geometric ergodicity proof. This extends a result on Markov chains due to Hajek (1982) to the area of stochastic approximation algorithms. We apply our results to several different Stochastic Approximation algorithms, specifically Projected Stochastic Gradient Descent, Kiefer-Wolfowitz and Stochastic Frank-Wolfe algorithms. When applicable, our results prove faster $O(1/t)$ and linear convergence rates for Projected Stochastic Gradient Descent with a non-vanishing gradient.
format Preprint
id arxiv_https___arxiv_org_abs_2208_07243
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Exponential Concentration in Stochastic Approximation
Law, Kody
Walton, Neil
Yang, Shangda
Machine Learning
Optimization and Control
We analyze the behavior of stochastic approximation algorithms where iterates, in expectation, progress towards an objective at each step. When progress is proportional to the step size of the algorithm, we prove exponential concentration bounds. These tail-bounds contrast asymptotic normality results, which are more frequently associated with stochastic approximation. The methods that we develop rely on a geometric ergodicity proof. This extends a result on Markov chains due to Hajek (1982) to the area of stochastic approximation algorithms. We apply our results to several different Stochastic Approximation algorithms, specifically Projected Stochastic Gradient Descent, Kiefer-Wolfowitz and Stochastic Frank-Wolfe algorithms. When applicable, our results prove faster $O(1/t)$ and linear convergence rates for Projected Stochastic Gradient Descent with a non-vanishing gradient.
title Exponential Concentration in Stochastic Approximation
topic Machine Learning
Optimization and Control
url https://arxiv.org/abs/2208.07243