323,278 research outputs found
On affine scaling inexact dogleg methods for bound-constrained nonlinear systems
No full textWithin the framework of affine scaling trust-region methods for bound constrained problems, we discuss the use of a inexact dogleg method as a tool for simultaneously handling the trust-region and the bound constraints while seeking for an approximate minimizer of the model. Focusing on bound-constrained systems of nonlinear equations, an inexact affine scaling method for large scale problems, employing the inexact dogleg procedure, is described. Global convergence results are established without any Lipschitz assumption on the Jacobian matrix, and locally fast convergence is shown under standard assumptions. Convergence analysis is performed without specifying the scaling matrix used to handle the bounds, and a rather general class of scaling matrices is allowed in actual algorithms. Numerical results showing the performance of the method are also given
CODOSOL: a bound-constrained nonlinear equations solver
No full textCoDoSol is a Matlab code for medium scale constrained nonlinear systems of equations F(x)=0, l R^n, l and u are vectors of dimension n. Non-existent lower and upper bounds, i.e. entries of l and u equal to minus o plus infinity, are allowed.
The code is based on an affine scaling trust region algorithm. The algorithm combines Newton method and trust region procedures where the merit function used is the norm of the nonlinear residual. The trust region and the corresponding scaled gradient are defined by suitable diagonal scaling avoiding the problem of running directly into a bound. The trust region problem is approximately solved by a constrained dogleg method. Only strictly feasible iterates are generated.
A great flexibility in choosing the scaling matrix is allowed for application dependent purposes.
If the problem has sparse Jacobians and a relatively big size, the user can choose to work with sparse memory storage. Then, the Newton step is computed via the built-in Matlab function LU with the syntax for calling the UMFPACK package when Matlab 6.5 or later versions are used.
Various input/output options are provided, and we refer to the code itself for further documentation.
Accompanying paper:
Bellavia S., Macconi M., Pieraccini S. (2012), Constrained dogleg methods for nonlinear systems with simple bounds. In: COMPUTATIONAL OPTIMIZATION AND APPLICATIONS, vol. 53 n. 3, pp. 771-794. - ISSN 0926-600
Convergence analysis of an Inexact Infeasible Interior Point method for Semidefinite Programming
No full textIn this paper we present an extension to SDP of the well known infeasible Interior Point method for linear programming of Kojima,Megiddo and Mizuno (A primal-dual infeasible-interior-point algorithm for Linear Programming, Math. Progr., 1993). The extension developed here allows the use of inexact search directions; i.e., the linear systems defining the search directions can be solved with an accuracy that increases as the solution is approached. A convergence analysis is carried out and the global convergence of the method is prove
Numerical solution of KKT systems in PDE-constrained optimization problems via the affine scaling trust-region approach
No full textGlobalization strategies for Newton-Krylov methods for stabilized FEM discretization of Navier-Stokes equations
No full textIn this work we study the numerical solution of nonlinear systems arising from stabilized FEM discretizations of Navier-Stokes equations. This is a very challenging problem and often inexact Newton solvers present severe difficulties to converge. Then, they must be wrapped into a globalization strategy. We consider the classical backtracking procedure, a subspace trust-region strategy and an hybrid approach. This latter strategy is proposed with the aim of improve the robustness of backtracking and it is obtained combining the backtracking procedure and the elliptical subspace trust-region strategy. Under standard assumptions, we prove global and fast convergence of the inexact Newton methods embedded in this new strategy as well as in the subspace trust-region procedure. Computational results on classical CFD benchmarks are performed. Comparisons among the classical backtracking strategy, the elliptical subspace trust-region approach and the hybrid procedure are presented. Our numerical experiments show the effectiveness of the proposed hybrid technique
Theatermania and investigation of the Self
No full textIl teatro non solo scritto e fruito, ma anche agito, con la possibilità che offre di calarsi nei ruoli,
nelle situazioni e nelle emozioni più diverse, diventa spesso, per molti, l’unica via di fuga dalle strettoie
sociali. È su questo aspetto che si concentra il contributo dell'autrice, che da storica del teatro riflette sul fenomeno ‘teatromania’ dalla prospettiva precipua
dell’attore
Introduction. Theatermania: Presentation
No full textLa presentazione costituisce una introduzione ragionata al volume collettaneo: Theatermania in Eighteenth-Century Europe
Analyses anthracologiques et carpologiques dans la villa de « La Fontainotte » à Grand (Vosges, 88)
No full textIn: Gazenbeek M. (dir.), Bellavia V., Braguier S., Cabart H., La Domus d'un notable romain : Grand, Vosges, La Fontainotte : rapport de fouilles, Rapport de fouille. Inrap Grand Est Nord
Analyses anthracologiques et carpologiques dans la villa de « La Fontainotte » à Grand (Vosges, 88)
No full textIn: Gazenbeek M. (dir.), Bellavia V., Braguier S., Cabart H., La Domus d'un notable romain : Grand, Vosges, La Fontainotte : rapport de fouilles, Rapport de fouille. Inrap Grand Est Nord
Analyses anthracologiques et carpologiques dans la villa de « La Fontainotte » à Grand (Vosges, 88)
No full textIn: Gazenbeek M. (dir.), Bellavia V., Braguier S., Cabart H., La Domus d'un notable romain : Grand, Vosges, La Fontainotte : rapport de fouilles, Rapport de fouille. Inrap Grand Est Nord
- …
