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In this paper we generalize the strongly convergent Krasnoselskii- Mann-type iteration for families of nonexpansive mappings defined recently by Bo\c{t} and Meier in Hilbert spaces to the abstract setting of W - hyperbolic spaces and we…

Optimization and Control · Mathematics 2023-06-16 Horaţiu Cheval

In this paper we use proof mining methods to compute rates of ($T$-)asymptotic regularity of the generalized Krasnoselskii-Mann-type iteration associated to a nonexpansive mapping $T:X\to X$ in a uniformly convex normed space $X$. For…

Optimization and Control · Mathematics 2025-01-23 Paulo Firmino , Laurentiu Leustean

We apply proof mining techniques to obtain quantitative and qualitative results on asymptotic and T-asymptotic regularity for the inexact generalized Halpern iteration, a viscosity-type extension of an iteration recently studied by Kanzow…

Optimization and Control · Mathematics 2026-03-19 Nicoleta Dumitru , Laurentiu Leustean

We analyze the oracle complexity of the stochastic Halpern iteration with minibatch, where we aim to approximate fixed-points of nonexpansive and contractive operators in a normed finite-dimensional space. We show that if the underlying…

Optimization and Control · Mathematics 2025-05-13 Mario Bravo , Juan Pablo Contreras

We show that the asymptotic regularity and the strong convergence of the modified Halpern iteration due to T.-H. Kim and H.-K. Xu and studied further by A. Cuntavenapit and B. Panyanak and the Tikhonov-Mann iteration introduced by H. Cheval…

Optimization and Control · Mathematics 2023-03-15 Horatiu Cheval , Ulrich Kohlenbach , Laurentiu Leustean

In this note we apply a lemma due to Sabach and Shtern to compute linear rates of asymptotic regularity for Halpern-type nonlinear iterations studied in optimization and nonlinear analysis.

Optimization and Control · Mathematics 2024-05-01 Horaţiu Cheval , Laurenţiu Leuştean

In this paper we obtain new effective results on the Halpern iterations of nonexpansive mappings using methods from mathematical logic or, more specifically, proof-theoretic techniques. We give effective rates of asymptotic regularity for…

Functional Analysis · Mathematics 2007-10-10 Laurentiu Leustean

We introduce novel convergence results for asynchronous iterations that appear in the analysis of parallel and distributed optimization algorithms. The results are simple to apply and give explicit estimates for how the degree of asynchrony…

Optimization and Control · Mathematics 2023-04-04 Hamid Reza Feyzmahdavian , Mikael Johansson

We investigate the Stochastic Krasnoselskii-Mann iterations for expected nonexpansive fixed-point problems in a real Hilbert space. We establish convergence guarantees under significantly weaker assumptions on the variance than those…

Optimization and Control · Mathematics 2026-05-12 Daniel Cortild , Coralia Cartis

In this paper, we compute quadratic rates of asymptotic regularity for the Tikhonov-Mann iteration in W-hyperbolic spaces. This iteration is an extension to a nonlinear setting of the modified Mann iteration defined recently by Bot, Csetnek…

Optimization and Control · Mathematics 2022-02-21 Horatiu Cheval , Laurentiu Leustean

In this paper we consider, in the general context of CAT(0) spaces, an iterative schema which alternates between Halpern and Krasnoselskii-Mann style iterations. We prove, under suitable conditions, the strong convergence of this algorithm,…

Functional Analysis · Mathematics 2023-03-10 Bruno Dinis , Pedro Pinto

The Krasnosel'ski\u{\i}--Mann and Halpern iterations are classical schemes for approximating fixed points of nonexpansive mappings in Banach spaces, and have been widely studied in more general frameworks such as $CAT(\kappa)$ and, more…

Optimization and Control · Mathematics 2026-03-24 Katherine Rossella Foglia , Vittorio Colao

Machine learning approaches relying on such criteria as adversarial robustness or multi-agent settings have raised the need for solving game-theoretic equilibrium problems. Of particular relevance to these applications are methods targeting…

Machine Learning · Computer Science 2023-10-27 Xufeng Cai , Ahmet Alacaoglu , Jelena Diakonikolas

We study Krasnoselskii-Mann style iterative algorithms for approximating fixpoints of asymptotically weakly contractive mappings, with a focus on providing generalised convergence proofs along with explicit rates of convergence. More…

Functional Analysis · Mathematics 2021-04-30 Thomas Powell , Franziskus Wiesnet

In this paper we establish an estimate for the rate of convergence of the Krasnosel'ski\v{\i}-Mann iteration for computing fixed points of non-expansive maps. Our main result settles the Baillon-Bruck conjecture [3] on the asymptotic…

Optimization and Control · Mathematics 2013-10-09 Roberto Cominetti , José A. Soto , José Vaisman

In this paper we apply proof mining techniques to compute, in the setting of CAT$(\kappa)$ spaces (with $\kappa >0$), effective and highly uniform rates of asymptotic regularity and metastability for a nonlinear generalization of the…

Functional Analysis · Mathematics 2015-07-29 Laurentiu Leustean , Adriana Nicolae

The Halpern iteration for solving monotone inclusion problems has gained increasing interests in recent years due to its simple form and appealing convergence properties. In this paper, we investigate the inexact variants of the scheme in…

Optimization and Control · Mathematics 2025-05-28 Ling Liang , Zusen Xu , Kim-Chuan Toh , Jia-Jie Zhu

In this paper we obtain a quadratic bound on the rate of asymptotic regularity for the Krasnoselski-Mann iterations of nonexpansive mappings in CAT(0)-spaces, whereas previous results guarantee only exponential bounds. The method we use is…

Functional Analysis · Mathematics 2007-05-23 Laurentiu Leustean

In this paper we extend to $UCW$-hyperbolic spaces the quantitative asymptotic regularity results for the alternating Halpern-Mann iteration obtained by Dinis and the second author for CAT(0) spaces. These results are new even for uniformly…

Optimization and Control · Mathematics 2023-02-28 Laurentiu Leustean , Pedro Pinto

We study stochastic monotone inclusion problems, which widely appear in machine learning applications, including robust regression and adversarial learning. We propose novel variants of stochastic Halpern iteration with recursive variance…

Optimization and Control · Mathematics 2023-01-10 Xufeng Cai , Chaobing Song , Cristóbal Guzmán , Jelena Diakonikolas
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