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276 discussions

Nello Cristianini a Pisa
by Gianna M. Del Corso 20 May '25

20 May '25

Cari colleghi, Giovedì 22/5 alle 11:00 nell’aula magna dell’ex facoltà di Scienze, Nello Cristianini, professore di intelligenza artificiale all’ Università di Bath terrà una presentazione del suo libro "Machina Sapiens <https://www.mulino.it/isbn/9788815384461>” discutendo dei rischi e delle implicazioni dell'AI generativa. Sarà un'ottima occasione per approfondire temi di grande attualità nel nostro campo con uno dei principali esperti dell'argomento, che li presenterà in modo accessibile. Vi incoraggio a partecipare e a contribuire alla discussione, invitando anche gli studenti del nostro corso di laurea. Cordiali saluti, Gianna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

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[Indico] Federica Mugnaioni, Optimal and Scalable Augmented Lagrangian preconditioners for Fictitious Domain problems, 13/05/2025, 11:00 Europe/Rome
by fabio.durastante＠unipi.it 12 May '25

12 May '25

Title: Optimal and Scalable Augmented Lagrangian preconditioners for Fictitious Domain problems, Speaker(s): Federica Mugnaioni, Scuola Normale Superiore, Date and time: 13 May 2025, 11:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Saletta Riunioni). You can access the full event here: https://events.dm.unipi.it/e/321 Abstract -------- One of the major drawbacks of using Fictitious Domain methods is the computational demands of solving the associated large-scale linear systems, both in terms of time and memory. To address this issue, we propose two augmented Lagrangian-based preconditioners for efficiently solving linear systems of equations with a block two-by-two and three-by-three structure arising from fictitious domain problems and from finite element discretizations of immersed boundary methods. We consider two relevant examples to illustrate the performance of these preconditioners when used in conjunction with flexible GMRES: the Poisson and the Stokes fictitious domain problems. We provide a detailed spectral analysis, deriving lower and upper bounds for the eigenvalues of the preconditioned matrix and showing their independence with respect to discretization parameters. Furthermore, we discuss the eigenvalue distribution when inexact versions of the preconditioners are employed. We show the effectiveness of the proposed approach and the robustness of our preconditioning strategies through extensive numerical tests in both two and three dimensions, using different immersed geometries.M. Benzi, M. Feder, L. Heltai and F. Mugnaioni. Optimal and Scalable Augmented Lagrangian preconditioners for Fictitious Domain problems. arXiv:2504.11339, 2025 Note ---- A reminder of tomorrow's seminar. -- Indico :: Email Notifier https://events.dm.unipi.it/e/321

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[Indico] Federica Mugnaioni, Optimal and Scalable Augmented Lagrangian preconditioners for Fictitious Domain problems, 13/05/2025, 11:00 Europe/Rome
by fabio.durastante＠unipi.it 28 Apr '25

28 Apr '25

Title: Optimal and Scalable Augmented Lagrangian preconditioners for Fictitious Domain problems, Speaker(s): Federica Mugnaioni, Scuola Normale Superiore, Date and time: 13 May 2025, 11:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Saletta Riunioni). You can access the full event here: https://events.dm.unipi.it/e/321 Abstract -------- One of the major drawbacks of using Fictitious Domain methods is the computational demands of solving the associated large-scale linear systems, both in terms of time and memory. To address this issue, we propose two augmented Lagrangian-based preconditioners for efficiently solving linear systems of equations with a block two-by-two and three-by-three structure arising from fictitious domain problems and from finite element discretizations of immersed boundary methods. We consider two relevant examples to illustrate the performance of these preconditioners when used in conjunction with flexible GMRES: the Poisson and the Stokes fictitious domain problems. We provide a detailed spectral analysis, deriving lower and upper bounds for the eigenvalues of the preconditioned matrix and showing their independence with respect to discretization parameters. Furthermore, we discuss the eigenvalue distribution when inexact versions of the preconditioners are employed. We show the effectiveness of the proposed approach and the robustness of our preconditioning strategies through extensive numerical tests in both two and three dimensions, using different immersed geometries.M. Benzi, M. Feder, L. Heltai and F. Mugnaioni. Optimal and Scalable Augmented Lagrangian preconditioners for Fictitious Domain problems. arXiv:2504.11339, 2025 -- Indico :: Email Notifier https://events.dm.unipi.it/e/321

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Colloquium 17 aprile ore 16.00
by Stefano Massei 15 Apr '25

15 Apr '25

Cari tutti, a nome della Commissione Colloquia di Dipartimento, vi ricordo che giovedì 17 aprile alle 16.00 in AULA MAGNA Virginie Ehrlacher<https://team.inria.fr/matherials/team-members/virginie-ehrlacher-galland/> (Ecole des Ponts ParisTech) terrà un <https://www.dm.unipi.it/en/seminar/?id=67a64aff762f5b32f7b4dfd3> colloquium<https://www.dm.unipi.it/en/seminar/?id=67a64aff762f5b32f7b4dfd3> sul tema: “A sparse approximation of the Lieb functional with moment constraints”. Cordiali saluti, Stefano Massei

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Next NUMPI seminar: set the date
by Fabio Durastante 15 Apr '25

15 Apr '25

Good morning, We would like to fix the date for the next NUMPI seminar in May. It will be a seminar held by Federica Mugnaioni (Ph.D. Scuola Normale Superiore) on the topic of preconditioners for discretization of fictitious domain problems. Please reply with your availability for the days of May 12/13 and we will try to organize it at a time convenient for most of us: https://date.dm.unipi.it/Vh6AwjL3MKGWBESp Best, Fabio

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[Indico] Raf Vandebril, On inverse eigenvalue problems for multiple orthogonal polynomials, 14/04/2025, 11:30 Europe/Rome
by leonardo.robol＠unipi.it 14 Apr '25

14 Apr '25

Title: On inverse eigenvalue problems for multiple orthogonal polynomials, Speaker(s): Raf Vandebril, KU Leuven, Date and time: 14 Apr 2025, 11:30 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Saletta Riunioni). You can access the full event here: https://events.dm.unipi.it/e/318 Abstract -------- Multiple orthogonal polynomials (MOP's) arise in various applications, including approximation theory, random matrix theory, and numerical integration. To define MOP's, one needs multiple inner products, leading to two types of MOP’s, which are mutually biorthogonal. These MOP's satisfy recurrence relations, which can be linked to linear algebra, via discretization. As a result we get an inverse eigenvalue problem to retrieve the matrix of recurrences directly. We provide two algorithms for solving the inverse eigenvalue problem, one based on classical equivalence transformations and one linked to (block) Krylov methods. Numerical illustrations are provided to demonstrate correctness of the approach and also reveal the strong sensitivity of the problem. -- Indico :: Email Notifier https://events.dm.unipi.it/e/318

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[Indico] Raf Vandebril, On inverse eigenvalue problems for multiple orthogonal polynomials, 14/04/2025, 11:30 Europe/Rome
by leonardo.robol＠unipi.it 08 Apr '25

08 Apr '25

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[Indico] Prof. Michiel Hochstenbach, Recent Progress in Steplengths in Gradient Methods for Unconstrained Optimization, 3/27/25, 2:00 PM Europe/Rome
by stefano.massei＠unipi.it 26 Mar '25

26 Mar '25

Title: Recent Progress in Steplengths in Gradient Methods for Unconstrained Optimization, Speaker(s): Prof. Michiel Hochstenbach, Eindhoven University of Technology, Date and time: Mar 27, 2025, 2:00 PM (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di matematica (Aula riunioni). You can access the full event here: https://events.dm.unipi.it/e/314 Abstract -------- We review recent progress in stepsizes in gradient methods for unconstrained numerical optimization, for both quadratic and general nonlinear problems, including several very valuable contributions from Italian experts such as Prof. Zanni and colleagues. We will review Barzilai-Borwein steps and secant equations, and show developments in harmonic stepsizes and homogeneous secant equations. The key idea is that the steplength is selected as the inverse Ritz value of an average Hessian. For limited memory methods, we will address several challenges, including how to avoid negative or non-real stepsize candidates. We will also present some open problems. This talk reflects joint work with Giulia Ferrandi. -- Indico :: Email Notifier https://events.dm.unipi.it/e/314

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Discussione tesi di dottorato di Alberto Bucci
by Leonardo Robol 21 Feb '25

21 Feb '25

Cari tutti e tutte, lunedì 24/02, alle 10.00, Alberto Bucci discuterà la sua tesi di dottorato in Aula Magna del Dipartimento di Matematica. Il titolo della tesi è "Randomized techniques for low-rank approximation of matrices and tensors with applications". Chiunque volesse partecipare è benvenuto/a! A presto, -- Leonardo.

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Online seminar at University of Rome "Tor Vergata": Stefano Pozza: 6 febbraio alle 12:30
by Fabio Durastante 29 Jan '25

29 Jan '25

Dear everybody, Forwarding of a NA seminar announcement that can also be followed online at the University of Rome "Tor Vergata". Best, Fabio ________________________________ Da: Mariarosa Mazza <mariarosa.mazza(a)uniroma2.it> Inviato: mercoledì 29 gennaio 2025 18:49 A: mariarosa.mazza(a)uniroma2.it Oggetto: seminario Pozza: 6 febbraio alle 12:30 Car* tutt*, giovedi 6 febbraio alle 12.30 in aula Dal Passo, Dipartimento di Matematica, Roma Tor Vergata, il Dott. Stefano Pozza (Charles University) terrà un seminario dal titolo (abstract in calce): "How to express the solution of an ODE as a linear system (in a suitable algebra) and exploit it for fast computation and network analysis". Il seminario può essere seguito online usando il link: https://teams.microsoft.com/l/meetup-join/19%3ad48916dee7364e0bbb08216ea621… Vi prego di diffondere l'annuncio fra i possibili interessati. Un caro saluto e grazie, Mariarosa --------------------------------------- Abstract: The solution of systems of non-autonomous linear ordinary differential equations is crucial in various applications, such as nuclear magnetic resonance spectroscopy. We introduced a new solution expression in terms of a generalization of the Volterra composition. Such an expression is linear in a particular algebraic structure of distributions, which can be mapped onto a subalgebra of infinite matrices. It is possible to exploit the new expression to devise fast numerical methods for linear non-autonomous ODEs. As a first example, we present a new method for the operator solution of the generalized Rosen-Zener model, a system of linear non-autonomous ODEs from quantum mechanics. The new method’s computing time scales linearly with the model’s size in the numerical experiments. A second example is the analysis of temporal network, where the new expression might lead to novel extension of subgraph centrality indexes. -- ------------------------------------- Dr. Mariarosa Mazza University of Rome Tor Vergata Via della Ricerca Scientifica, 1 00133, Rome, Italy Email: mariarosa.mazza(a)uniroma2.it<mailto:mariarosa.mazza@uniroma2.it> Tel: 0039 06-7259-4636 Url: https://sites.google.com/site/mariarosamazza1/ ---------------------------------

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