Complexity analysis of trust-region methods under (α,L0,L1)-smoothness
Abstract
Generalized smoothness assumptions have attracted growing attention in recent years, motivated in part by machine learning problems in which the gradient of the objective function may not be Lipschitz continuous. Among the most prominent of these is the (α, L0, L1)-smoothness assumption. Existing methods that attain the best known complexity bounds require knowledge of, or upper bounds on, α, L0 and L1, while the few parameter-agnostic methods available do not recover those bounds. In this paper, we show that trust-region methods attain the best known bounds for (α, L0, L1)-smooth objective functions without prior knowledge of these parameters. Establishing these results requires new analytical tools, beyond those used in classical trust-region complexity analyses. We further show that our working model assumption allows the use of general model Hessian approximations and, in particular, accommodates limited-memory quasi-Newton updates. Finally, we show that our complexity bound is sharp in the nonconvex setting.
Related
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BibTeX
@misc{diouane2026complexity,
title = {{Complexity analysis of trust-region methods under $(α,L_0,L_1)$-smoothness}},
author = {Youssef Diouane and Mohamed L. Habiboullah and Awa Khouna and Dominique Orban},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.33238},
eprint = {2609.33238},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.33238},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Complexity analysis of trust-region methods under (α,L_0,L_1)-smoothness
AU - Youssef Diouane
AU - Mohamed L. Habiboullah
AU - Awa Khouna
AU - Dominique Orban
PY - 2026
DA - 2026/09/27
PB - arXiv
DO - 10.48550/arxiv.2609.33238
UR - https://arxiv.org/abs/2609.33238
AB - Generalized smoothness assumptions have attracted growing attention in recent years, motivated in part by machine learning problems in which the gradient of the objective function may not be Lipschitz continuous. Among the most prominent of these is the (α, L_0, L_1)-smoothness assumption. Existing methods that attain the best known complexity bounds require knowledge of, or upper bounds on, α, L_0 and L_1, while the few parameter-agnostic methods available do not recover those bounds. In this paper, we show that trust-region methods attain the best known bounds for (α, L_0, L_1)-smooth objective functions without prior knowledge of these parameters. Establishing these results requires new analytical tools, beyond those used in classical trust-region complexity analyses. We further show that our working model assumption allows the use of general model Hessian approximations and, in particular, accommodates limited-memory quasi-Newton updates. Finally, we show that our complexity bound is sharp in the nonconvex setting.
ER -