arXiv Machine Learning By Wei Jiang, Sifan Yang, Wenhao Yang, Yibo Wang, Yuanyu Wan, Zechao Li, Lijun Zhang

Projection-Free Multi-level Algorithms for Stochastic Constrained Compositional Optimization

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arXiv Machine Learning
Oct 3

Optimal Momentum Methods for Stochastic Multilevel Compositional Optimization

The paper studies stochastic multi‑level optimization where the objective is a nested composition of smooth non‑convex functions. It introduces momentum‑based estimators that track function values at each level, achieving an optimal sample complexity of ≠(ε⁻⁴) for finding an ε‑stationary point without relying on average smoothness assumptions. The authors also present a batch‑free variant using first‑order approximations and clipping, and demonstrate the methods on risk‑averse portfolio optimization and hierarchical tilted empirical risk minimization.

By Wei Jiang, Rui Yan, Sifan Yang, Yuanyu Wan, Lijun Zhang, Zechao Li
arXiv Machine Learning
Jun 24

Constrained Variable Projection for Structured Problems

arXiv:2606. 23939v1 Announce Type: cross Abstract: Variable projection is a classical technique for separable nonlinear least-squares problems, in which variables that enter linearly are eliminated exactly, yielding a reduced nonlinear problem.

By Emanuele Zangrando, Sara Venturini, Francesco Rinaldi, Francesco Tudisco
arXiv Machine Learning
Jul 2

Towards Weaker Variance Assumptions for Stochastic Optimization

arXiv:2504. 09951v2 Announce Type: replace-cross Abstract: We revisit a classical assumption for analyzing stochastic gradient algorithms where the squared norm of the stochastic subgradient (or the variance for smooth problems) is allowed to grow as fast as the squared norm of the optimization variable.

By Ahmet Alacaoglu, Yura Malitsky, Stephen J. Wright