Analysis of Gradient Descent with Varying Step Sizes using Integral Quadratic Constraints

Fuente: arXiv
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Auteurs principaux: Padmanabhan, Ram, Seiler, Peter
Format: Preprint
Publié: 2022
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author Padmanabhan, Ram
Seiler, Peter
author_facet Padmanabhan, Ram
Seiler, Peter
contents The framework of Integral Quadratic Constraints (IQCs) is used to perform an analysis of gradient descent with varying step sizes. Two performance metrics are considered: convergence rate and noise amplification. We assume that the step size is produced from a line search and varies in a known interval. Modeling the algorithm as a linear, parameter-varying (LPV) system, we construct a parameterized linear matrix inequality (LMI) condition that certifies algorithm performance, which is solved using a result for polytopic LPV systems. Our results provide convergence rate guarantees when the step size lies within a restricted interval. Moreover, we recover existing rate bounds when this interval reduces to a single point, i.e. a constant step size. Finally, we note that the convergence rate depends only on the condition number of the problem. In contrast, the noise amplification performance depends on the individual values of the strong convexity and smoothness parameters, and varies inversely with them for a fixed condition number.
format Preprint
id arxiv_https___arxiv_org_abs_2210_00644
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Analysis of Gradient Descent with Varying Step Sizes using Integral Quadratic Constraints
Padmanabhan, Ram
Seiler, Peter
Optimization and Control
Systems and Control
The framework of Integral Quadratic Constraints (IQCs) is used to perform an analysis of gradient descent with varying step sizes. Two performance metrics are considered: convergence rate and noise amplification. We assume that the step size is produced from a line search and varies in a known interval. Modeling the algorithm as a linear, parameter-varying (LPV) system, we construct a parameterized linear matrix inequality (LMI) condition that certifies algorithm performance, which is solved using a result for polytopic LPV systems. Our results provide convergence rate guarantees when the step size lies within a restricted interval. Moreover, we recover existing rate bounds when this interval reduces to a single point, i.e. a constant step size. Finally, we note that the convergence rate depends only on the condition number of the problem. In contrast, the noise amplification performance depends on the individual values of the strong convexity and smoothness parameters, and varies inversely with them for a fixed condition number.
title Analysis of Gradient Descent with Varying Step Sizes using Integral Quadratic Constraints
topic Optimization and Control
Systems and Control
url https://arxiv.org/abs/2210.00644