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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

This paper provides an effective uniform rate of metastability (in the sense of Tao) on the strong convergence of Halpern iterations of nonexpansive mappings in CAT(0) spaces. The extraction of this rate from an ineffective proof due to…

Functional Analysis · Mathematics 2012-06-11 Ulrich Kohlenbach , Laurentiu Leustean

We use techniques of proof mining to extract a uniform rate of metastability (in the sense of Tao) for the strong convergence of approximants to fixed points of uniformly continuous pseudocontractive mappings in Banach spaces which are…

Functional Analysis · Mathematics 2020-01-17 Ulrich Kohlenbach , Andrei Sipos

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

Using proof-theoretical techniques, we analyze a proof by H.-K. Xu regarding a result of strong convergence for the Halpern type proximal point algorithm. We obtain a rate of metastability (in the sense of T. Tao) and also a rate of…

Functional Analysis · Mathematics 2020-01-01 Pedro Pinto

Alternative iterative methods for a nonexpansive mapping in a Banach space are proposed and proved to be convergent to a common solution to a fixed point problem and a variational inequality. We give rates of asymptotic regularity for such…

Functional Analysis · Mathematics 2009-06-01 Vittorio Colao , Laurentiu Leustean , Genaro Lopez , Victoria Martin-Marquez

Bauschke and Moursi have recently obtained results that implicitly contain the fact that the composition of finitely many averaged mappings on a Hilbert space that have approximate fixed points also has approximate fixed points and thus is…

Optimization and Control · Mathematics 2022-11-22 Andrei Sipos

In this study, we introduce a new iterative processes to approximate common fixed points of an infinite family of quasi-nonexpansive mappings and obtain a strongly convergent iterative sequence to the common fixed points of these mappings…

Functional Analysis · Mathematics 2015-02-24 K. Dogan , V. Karakaya

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

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, relying on methods from proof mining, we provide a quantitative analysis of a theorem due to Xu, stating that an iteration strongly converges to the solution of a well known quadratic optimization problem. Rates of…

Optimization and Control · Mathematics 2025-06-16 Paulo Firmino

This paper investigates the minimax-optimality of Halpern fixed-point iterations for Lipschitz maps in general normed spaces. Starting from an a priori bound on the orbit of iterates, we derive non-asymptotic estimates for the fixed-point…

Optimization and Control · Mathematics 2026-01-23 Mario Bravo , Roberto Cominetti , Jongmin Lee

In this paper, we obtain rates of metastability for the Tikhonov-Mann iteration for countable families of mappings in CAT(0) spaces. This iteration was recently defined by the author in the setting of W-hyperbolic spaces as a generalization…

Optimization and Control · Mathematics 2024-06-06 Horatiu Cheval

Let $X$ be a real Banach space with a normalized duality mapping uniformly norm-to-weak$^\star$ continuous on bounded sets or a reflexive Banach space which admits a weakly continuous duality mapping $J_{\Phi}$ with gauge $\phi$. Let $f$ be…

Optimization and Control · Mathematics 2007-12-10 Jean-Philippe Chancelier

We apply proof mining methods to analyse a result of Boikanyo and Moro\c{s}anu on the strong convergence of a Halpern-type proximal point algorithm. As a consequence, we obtain quantitative versions of this result, providing uniform…

Optimization and Control · Mathematics 2021-03-01 Laurentiu Leustean , Pedro Pinto

This paper is a close follow-up of Kaltenbacher and Tomba 2013 and Jin 2012, where Newton-Landweber iterations have been shown to converge either (unconditionally) without rates or (under an additional regularity assumption) with rates. The…

Numerical Analysis · Mathematics 2014-08-22 Barbara Kaltenbacher , Ivan Tomba

Kohlenbach and the author have extracted a rate of metastability for approximate curves associated to continuous pseudocontractive self-mappings in Banach spaces which are uniformly convex and uniformly smooth, whose convergence is due to…

Functional Analysis · Mathematics 2023-11-14 Andrei Sipos

In this paper, we study $\Delta$- convergence of iterations for a sequence of strongly quasi-nonexpansive mappings as well as the strong convergence of the Halpern type regularization of them in Hadamard spaces. Then, we give some their…

Functional Analysis · Mathematics 2016-11-10 Hadi Khatibzadeh , Vahid Mohebbi

We propose an adaptive way to choose the anchoring parameters for the Halpern iteration to find a fixed point of a nonexpansive mapping in a real Hilbert space. We prove strong convergence of this adaptive Halpern iteration and obtain the…

Optimization and Control · Mathematics 2025-05-19 Songnian He , Hong-Kun Xu , Qiao-Li Dong , Na Mei

We further study averaged and firmly nonexpansive mappings in the setting of geodesic spaces with a main focus on the asymptotic behavior of their Picard iterates. We use methods of proof mining to obtain an explicit quantitative version of…

Functional Analysis · Mathematics 2013-10-03 Adriana Nicolae
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