Estudo Geralhttps://estudogeral.sib.uc.ptThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Tue, 26 May 2020 03:09:28 GMT2020-05-26T03:09:28Z5091A Study of Preconditioners for Network Interior Point Methodshttp://hdl.handle.net/10316/7745Title: A Study of Preconditioners for Network Interior Point Methods
Authors: Júdice, Joaquim; Patricio, João; Portugal, Luis; Resende, Mauricio; Veiga, Geraldo
Abstract: We study and compare preconditioners available for network interior point methods. We derive upper bounds for the condition number of the preconditioned matrices used in the solution of systems of linear equations defining the algorithm search directions. The preconditioners are tested using PDNET, a state-of-the-art interior point code for the minimum cost network flow problem. A computational comparison using a set of standard problems improves the understanding of the effectiveness of preconditioners in network interior point methods.
Wed, 01 Jan 2003 00:00:00 GMThttp://hdl.handle.net/10316/77452003-01-01T00:00:00ZThe eigenvalue complementarity problemhttp://hdl.handle.net/10316/7723Title: The eigenvalue complementarity problem
Authors: Júdice, Joaquim; Sherali, Hanif; Ribeiro, Isabel M.
Abstract: Abstract In this paper an eigenvalue complementarity problem (EiCP) is studied, which finds its origins in the solution of a contact problem in mechanics. The EiCP is shown to be equivalent to a Nonlinear Complementarity Problem, a Mathematical Programming Problem with Complementarity Constraints and a Global Optimization Problem. A finite Reformulation–Linearization Technique (Rlt)-based tree search algorithm is introduced for processing the EiCP via the lattermost of these formulations. Computational experience is included to highlight the efficacy of the above formulations and corresponding techniques for the solution of the EiCP.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10316/77232007-01-01T00:00:00ZOn the solution of the symmetric eigenvalue complementarity problem by the spectral projected gradient algorithmhttp://hdl.handle.net/10316/7714Title: On the solution of the symmetric eigenvalue complementarity problem by the spectral projected gradient algorithm
Authors: Júdice, Joaquim; Raydan, Marcos; Rosa, Silvério; Santos, Sandra
Abstract: Abstract This paper is devoted to the eigenvalue complementarity problem (EiCP) with symmetric real matrices. This problem is equivalent to finding a stationary point of a differentiable optimization program involving the Rayleigh quotient on a simplex (Queiroz et al., Math. Comput. 73, 1849–1863, 2004). We discuss a logarithmic function and a quadratic programming formulation to find a complementarity eigenvalue by computing a stationary point of an appropriate merit function on a special convex set. A variant of the spectral projected gradient algorithm with a specially designed line search is introduced to solve the EiCP. Computational experience shows that the application of this algorithm to the logarithmic function formulation is a quite efficient way to find a solution to the symmetric EiCP.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10316/77142008-01-01T00:00:00ZOn the solution of NP-hard linear complementarity problemshttp://hdl.handle.net/10316/7722Title: On the solution of NP-hard linear complementarity problems
Authors: Júdice, Joaquim; Faustino, Ana; Ribeiro, Isabel
Abstract: Abstract In this paper two enumerative algorithms for the Linear Complementarity Problems (LCP) are discussed. These procedures exploit the equivalence of theLCP into a nonconvex quadratic and a bilinear programs. It is shown that these algorithms are efficient for processing NP-hardLCPs associated with reformulations of the Knapsack problem and should be recommended to solve difficultLCPs.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10316/77222002-01-01T00:00:00ZCost minimization of a multiple section power cable supplying several remote telecom equipmenthttp://hdl.handle.net/10316/7715Title: Cost minimization of a multiple section power cable supplying several remote telecom equipment
Authors: Júdice, Joaquim; Anunciada, Victor; Baptista, Carlos
Abstract: Abstract An optimization problem is described, that arises in telecommunications and is associated with multiple cross-sections of a single power cable used to supply remote telecom equipments. The problem consists of minimizing the volume of copper material used in the cables and consequently the total cable cost. Two main formulations for the problem are introduced and some properties of the functions and constraints involved are presented. In particular it is shown that the optimization problems are convex and have a unique optimal solution. A Projected Gradient algorithm is proposed for finding the global minimum of the optimization problem, taking advantage of the particular structure of the second formulation. An analysis of the performance of the algorithm for given real-life problems is also presented.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10316/77152008-01-01T00:00:00ZGenerating box-constrained optimization problemshttp://hdl.handle.net/10316/10703Title: Generating box-constrained optimization problems
Authors: Facchinei, Francisco; Júdice, Joaquim; Soares, João
Abstract: We present a method for generating box-constrained nonlinear programming test problems. The technique allows the user to control some properties of the generated test problems that are know to influence the behavior of algorithms for their solution. A corresponding set of Fortran 77 routines is described in a companion algorithm (774).
Mon, 01 Sep 1997 00:00:00 GMThttp://hdl.handle.net/10316/107031997-09-01T00:00:00ZAlgorithm 774: Fortran subroutines for generating box-constrained optimization problemshttp://hdl.handle.net/10316/10702Title: Algorithm 774: Fortran subroutines for generating box-constrained optimization problems
Authors: Facchinei, Francisco; Júdice, Joaquim; Soares, João
Abstract: We describe a set of Fortran routines for generatig box-constrained nonlinear programming test problems. The technique, as described by Facchinei et al. (this issue), allows the user to control relevant properties of the generated problems.
Mon, 01 Sep 1997 00:00:00 GMThttp://hdl.handle.net/10316/107021997-09-01T00:00:00ZWorkforce planning in a lotsizing mail processing problemhttp://hdl.handle.net/10316/4622Title: Workforce planning in a lotsizing mail processing problem
Authors: Júdice, Joaquim; Martins, Pedro; Nunes, Jacinto
Abstract: The treatment of mail objects in a mail processing centre involves many operations, in particular sorting by destination. Out of the batching problem that we can identify in such a process, there are also staff planning concerns. In this paper, we analyse a treatment area (registered mail) belonging to a mail processing center, where mail objects are treated in a chain production process. The production quantities and the transfer amounts among machines are required to be determined along the daily work period. The objective is to minimize the costs with human resources needed in the process, linked with the lotsizing production plan, by matching staff to work requirements. This leads into a lotsizing and workforce problem, for which we propose an integer programming formulation. A case study of a particular treatment area is also discussed. The formulation is adjusted to the specific constraints of this case study and some computational results are included, considering average, small and high daily amounts of mail arrived to that particular treatment area.
Sat, 01 Jan 2005 00:00:00 GMThttp://hdl.handle.net/10316/46222005-01-01T00:00:00ZA Complementarity-based Partitioning and Disjunctive Cut Algorithm for Mathematical Programming Problems with Equilibrium Constraintshttp://hdl.handle.net/10316/7732Title: A Complementarity-based Partitioning and Disjunctive Cut Algorithm for Mathematical Programming Problems with Equilibrium Constraints
Authors: Júdice, Joaquim; Sherali, Hanif; Ribeiro, Isabel; Faustino, Ana
Abstract: Abstract In this paper a branch-and-bound algorithm is proposed for finding a global minimum to a Mathematical Programming Problem with Complementarity (or Equilibrium) Constraints (MPECs), which incorporates disjunctive cuts for computing lower bounds and employs a Complementarity Active-Set Algorithm for computing upper bounds. Computational results for solving MPECs associated with Bilivel Problems, NP-hard Linear Complementarity Problems, and Hinge Fitting Problems are presented to highlight the efficacy of the procedure in determining a global minimum for different classes of MPECs.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10316/77322006-01-01T00:00:00Z