Counter-examples in first-order optimization: a constructive approach

Fuente: arXiv
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Autores principales: Goujaud, Baptiste, Dieuleveut, Aymeric, Taylor, Adrien
Formato: Preprint
Publicado: 2023
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author Goujaud, Baptiste
Dieuleveut, Aymeric
Taylor, Adrien
author_facet Goujaud, Baptiste
Dieuleveut, Aymeric
Taylor, Adrien
contents While many approaches were developed for obtaining worst-case complexity bounds for first-order optimization methods in the last years, there remain theoretical gaps in cases where no such bound can be found. In such cases, it is often unclear whether no such bound exists (e.g., because the algorithm might fail to systematically converge) or simply if the current techniques do not allow finding them. In this work, we propose an approach to automate the search for cyclic trajectories generated by first-order methods. This provides a constructive approach to show that no appropriate complexity bound exists, thereby complementing the approaches providing sufficient conditions for convergence. Using this tool, we provide ranges of parameters for which some of the famous heavy-ball, Nesterov accelerated gradient, inexact gradient descent, and three-operator splitting algorithms fail to systematically converge, and show that it nicely complements existing tools searching for Lyapunov functions.
format Preprint
id arxiv_https___arxiv_org_abs_2303_10503
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Counter-examples in first-order optimization: a constructive approach
Goujaud, Baptiste
Dieuleveut, Aymeric
Taylor, Adrien
Optimization and Control
While many approaches were developed for obtaining worst-case complexity bounds for first-order optimization methods in the last years, there remain theoretical gaps in cases where no such bound can be found. In such cases, it is often unclear whether no such bound exists (e.g., because the algorithm might fail to systematically converge) or simply if the current techniques do not allow finding them. In this work, we propose an approach to automate the search for cyclic trajectories generated by first-order methods. This provides a constructive approach to show that no appropriate complexity bound exists, thereby complementing the approaches providing sufficient conditions for convergence. Using this tool, we provide ranges of parameters for which some of the famous heavy-ball, Nesterov accelerated gradient, inexact gradient descent, and three-operator splitting algorithms fail to systematically converge, and show that it nicely complements existing tools searching for Lyapunov functions.
title Counter-examples in first-order optimization: a constructive approach
topic Optimization and Control
url https://arxiv.org/abs/2303.10503