A rigorous decomposition approach to solve separable mixed-integer nonlinear programs where the participating functions are nonconvex is presented. The proposed algorithms consist of solving an alternating sequence of...
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A rigorous decomposition approach to solve separable mixed-integer nonlinear programs where the participating functions are nonconvex is presented. The proposed algorithms consist of solving an alternating sequence of Relaxed Master Problems (mixed-integer linear program) and two nonlinear programming problems (NLPs). A sequence of valid nondecreasing lower bounds and upper bounds is generated by the algorithms which converge in a finite number of iterations. A Primal Bounding Problem is introduced, which is a convex NLP solved at each iteration to derive valid outer approximations of the nonconvex functions in the continuous space. Two decomposition algorithms are presented in this work. On finite termination, the first yields the global solution to the original nonconvex MINLP and the second finds a rigorous bound to the global solution. Convergence and optimality properties, and refinement of the algorithms for efficient implementation are presented. Finally, numerical results are compared with currently available algorithms for example problems, illuminating the potential benefits of the proposed algorithm.
In this paper, we propose a new decomposition algorithm for solving monotone variational inequality problems with linear constraints. The algorithm utilizes the problem's structure conductive to decomposition. At ...
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In this paper, we propose a new decomposition algorithm for solving monotone variational inequality problems with linear constraints. The algorithm utilizes the problem's structure conductive to decomposition. At each iteration, the algorithm solves a system of nonlinear equations, which is structurally much easier to solve than variational inequality problems, the subproblems of classical decomposition methods, and then performs a projection step to update the multipliers. We allow to solve the subproblems approximately and we prove that under mild assumptions on the problem's data, the algorithm is globally convergent. We also report some preliminary computational results, which show that the algorithm is encouraging. (C) 2003 Elsevier B.V. All rights reserved.
For solving large-scale constrained separable variational inequality problems, the de-composition methods are attractive, since they solve the original problems via solving a series of small-scale problems, which may ...
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For solving large-scale constrained separable variational inequality problems, the de-composition methods are attractive, since they solve the original problems via solving a series of small-scale problems, which may be much easier to solve than the original problems. In this paper, we-propose some new decomposition methods, which axe based on the Lagrange and the augmented Lagrange mappings of the problems, respectively. For the global convergence, the first method needs the partial cocoercivity of the underlying mapping, while the second one just requires monotonicity, a condition which is much weaker than partial cocoercivity. The cost for this weaker condition is to perform two additional projection steps on the dual variables and the primal-dual variables. We then extend the method to a more practical one, which just solves the subproblem approximately. We also report some computational results of the inexact method to show its promise. (C) 2003 Elsevier Science Ltd. All rights reserved.
In this paper we discuss the problem of computing and analyzing the static equilibrium of a nonrigid water tank. Specifically, we fix the amount of water contained in the tank, modelled as a membrane. In addition, the...
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In this paper we discuss the problem of computing and analyzing the static equilibrium of a nonrigid water tank. Specifically, we fix the amount of water contained in the tank, modelled as a membrane. In addition, there are rigid obstacles that constrain the deformation. This amounts to a nonconvex variational problem. We derive the optimality system and its interpretation in terms of equilibrium of forces. A second-order sensitivity analysis, allowing to compute derivatives of solutions and a second-order Taylor expansion of the cost function, is performed, in spite of the fact that the cost function is not twice differentiable. We also study the finite elements discretization, introduce a decomposition algorithm for the numerical computation of the solution, and display numerical results. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.
This paper employs the Dantzig-Wolfe decomposition principle to solve linear programming models in a parallel-computing environment. Adopting the queuing discipline, we showed that under very general conditions, the p...
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This paper employs the Dantzig-Wolfe decomposition principle to solve linear programming models in a parallel-computing environment. Adopting the queuing discipline, we showed that under very general conditions, the proposed algorithm speedup trends toward a limiting value as the number of processors increases. (C) 2002 Elsevier Science Ltd. All rights reserved.
We analyze three variants of analytic barrier methods for minimization of a convex function under box-constraints: the classical method of analytic barriers (centres), the proximal method of analytic barriers and the ...
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We analyze three variants of analytic barrier methods for minimization of a convex function under box-constraints: the classical method of analytic barriers (centres), the proximal method of analytic barriers and the modified proximal method of analytic barriers. We give theoretical and practical complexity estimates of these methods and based on numerical tests outline their dependence on the used control parameters. We consider also the case where the objective function is not given in explicit analytic form and may not be defined everywhere.
We study the problem of carrying voice calls over a low-earth-orbit satellite network and present an analytical model for computing call-blocking probabilities for a single orbit of a satellite constellation. We have ...
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We study the problem of carrying voice calls over a low-earth-orbit satellite network and present an analytical model for computing call-blocking probabilities for a single orbit of a satellite constellation. We have devised a method to solve the corresponding Markov process efficiently for orbits of up to five satellites. For orbits consisting of a larger number of satellites, we have developed an approximate decomposition algorithm to compute the call-blocking probabilities by decomposing the system into smaller subsystems and iteratively solving each subsystem in isolation using the exact Markov process. Our approach can capture blocking due to handoffs for both satellite-fixed and earth-fixed constellations. Numerical results demonstrate that our method is accurate for a wide range of traffic patterns and for orbits with a number of satellites that is representative of commercial satellite systems.
We examine an oracle-type method to minimize a convex function f over a convex polyhedron G. The method is an extension of the level-method to the case, when f is a not everywhere finite function, i.e., it may equal t...
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We examine an oracle-type method to minimize a convex function f over a convex polyhedron G. The method is an extension of the level-method to the case, when f is a not everywhere finite function, i.e., it may equal to +infinity at some points of G. An estimate of its efficiency is given, and some modifications of the method are mentioned. Finally, we indicate possible ways of its employment and report results of a numerical experiment.
We study a class of circuit-switched wavelength-routing networks with fixed or alternate routing and with random wavelength allocation. We present an iterative path decomposition algorithm to evaluate accurately and e...
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We study a class of circuit-switched wavelength-routing networks with fixed or alternate routing and with random wavelength allocation. We present an iterative path decomposition algorithm to evaluate accurately and efficiently the blocking performance of such networks with and without wavelength converters. Our iterative algorithm analyzes the original network by decomposing it into single-path subsystems. These subsystems are analyzed in isolation, and the individual results are appropriately combined to obtain a solution for the overall network, To analyze individual subsystems, we first construct an exact Markov process that captures the behavior of a path in terms of wavelength use. We also obtain an approximate Markov process which has a closed-form solution that can be computed efficiently for short paths, We then develop an iterative algorithm to analyze approximately arbitrarily long paths. The path decomposition approach naturally captures the correlation of both link loads and link blocking events, Our algorithm represents a simple and computationally efficient solution to the difficult problem of computing call-blocking probabilities in wavelength-routing networks. We also demonstrate how our analytical techniques can be applied to gain insight into the problem of converter placement in wavelength-routing networks.
We analyze a novel two-level queueing network with blocking, consisting of N level-1 parallel queues linked to M level-2 parallel queues. The processing of a customer by a level-1 server requires additional services t...
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We analyze a novel two-level queueing network with blocking, consisting of N level-1 parallel queues linked to M level-2 parallel queues. The processing of a customer by a level-1 server requires additional services that are exclusively offered by level-2 servers. These level-2 servers are accessed through blocking and non-blocking messages issued by level-1 servers. If a blocking message is issued, the level-1 server gets blocked until the message is fully processed at the level-2 server. The queueing network is analyzed approximately using a decomposition method, which can be viewed as a generalization of the well-known two-node decomposition algorithm used to analyze tandem queueing networks with blocking. Numerical tests show that the algorithm has a good accuracy.
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