Browsing by Author "Longo, A."
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Item Conservative approximations in nonlinear optimization. theory and examples(1991) Longo, A.; Nó, M.; Aizpitarte, M.; Unzueta, J.; Centros PRE-FUSION TECNALIA - (FORMER)A new nonlinear optimization approach with strong convergence properties is presented. This approach is based on approximate subproblems, a nondifferentiable penalty function and a set active strategy, and is well suited for solution of design problems in engineering, where the number of variables may be large and function and gradient evaluations are very expensive (e.g. in structural optimization). The main theoretical results are presented, which lead to a general algorithm from which well-known methods (e.g. Pschenichny's baseline, method of hybrid approximations) can be seen as particular cases. Also, a new kind of convex approximation called SOC (second order correction) is introduced in this context, and some examples are solved by a practical algorithm implemented in a C module called ACPM.Item A general related variational approach to shape optimum design(1993) Longo, A.; Unzueta, J.; Schaeidt, E.; Alvarez, A.; Anza, J. J.; Centros PRE-FUSION TECNALIA - (FORMER); Desarrollo Corporativo; PROMETALA general variational approach to shape optimum design is presented. The paper is concerned mainly with two fundamental subjects involved within shape optimization methodologies: the Geometric Representation or Design Model definition and the evaluation of shape sensitivities. Within this context, the term variational is related, on one hand, to the use of variational geometry concepts at the level of Design Model and, on the other hand, to the evaluation of sensitivities by means of the material derivative concept or generalized calculus of variations. At the end of the paper, an industrial application, called SIDOMAT, is described, in order to show how these methodologies can be integrated in a shape optimum design system for practical use.Item New implementation of the boundary element method using a B-rep geometric modeller(1996) Casado, S.; Longo, A.; PROMETAL; Centros PRE-FUSION TECNALIA - (FORMER)In this paper, a new implementation of the Boundary Element Method using an interface with a B-rep geometric modeller, is presented. The main advantage of this approach is the capability to work with an exact representation of the geometry of the model. The analyzer is able to get, from a B-rep model representation, all the geometric information; so it does not need to mesh the model. The method is applied to 3D potential problem - Laplace's equation, but it is straight forward to apply to other problems (e.g. mechanical). Numerical results, for several electrostatics examples are shown.Item Optimisation of electromagnetic design using HPCN(Springer Verlag, 1998) Riley, C. P.; McLatchie, R. C.F.; Janssen, R.; Longo, A.; Gutiérrez, T.; Casado, S.; Simkin, J.; Brochet, P.; Molinari, G.; Alotto, P.; Lemoine, J. F.; Drago, G.; Sloot, Peter; Hertzberger, Bob; Bubak, Marian; Centros PRE-FUSION TECNALIA - (FORMER); CIRMETAL; PROMETALThe development of HPCN and portable parallel implementations through BSP has encouraged developers and users of electromagnetic design software to address both the “grand challenge” problems and replace analysis of a design with synthesis. The paper describes the approach adopted by the EPOCH consortium.Item Project MIDAS: Magnet Integrated Design and Analysis System(1997) Colyer, B.; Simkin, J.; Trowbridge, C. W.; Barberis, U.; Picco, E.; Gutierrez, T.; Longo, A.; Greenough, C.; Thomas, D.; Alotto, P.; Molfino, P.; Molinari, G.; Jared, G.; Sormaz, N.; CIRMETAL; Centros PRE-FUSION TECNALIA - (FORMER)Results from a European collaborative project to create an open system for engineering design, with particular emphasis toward electromagnetic devices, are presented. The system, code named MIDAS, is based on the new ISO STEP standard for data exchange and utilises state-of-the-art Graphical User Interfaces, 3D Geometric Modelling and three-dimensional automatic mesh generation with an advanced 2D subsetItem Tuning LAPACK codes on hierarchical memory machines(1996-06) Ojanguren, M.; Alvarez, A.; Anza, J.; Longo, A.; Centros PRE-FUSION TECNALIA - (FORMER); PROMETALAs important as the advance of computer technology is the development of suitable software for the exploitation of computer capacity. In this sense LAPACK (Anderson et al., LAPACK User's Guide, release 1.0, SIAM, Philadelphia, 1992) appears as the most efficient library in the dense linear algebra field, obtaining good results on vector and parallel computers, and in general, on hierarchical memory machines. However, some deficiencies in the general matrix LU decomposition were detected in DGETRF subroutine. On hierarchical memory machines not only the cache and TLB faults have to be minimized, but also the page faults, which cause excessive I/O operations. The blocking strategy used by DGETRF (and LAPACK in general) makes good use of the cache memory, but does not seem to be enough to avoid unnecessary I/O operations. Therefore, DGETRF does not provide satisfactory run times for large dimension matrices. In this paper a new code using a double blocking strategy will be described, which attains better run times than DGETRF.