INFORMS Journal on Computing articles from June 2007

INFORMS Journal on Computing archives from June 2007

From the editor.(Editorial)(Viewpoint essay)
June 22, 2007... As an engineer I am focussed on developing systems that function effectively, efficiently, and correctly. In the field of operations research, that usually means computer software and hardware that carry out calculations to simulate, optimize,...

Efficient computation of overlapping variance estimators for simulation.
June 22, 2007... For a steady-state simulation output process, we formulate efficient algorithms to compute certain estimators of the process variance parameter (i.e., the sum of covariances at all lags), where the estimators are derived in principle from...

Scatter search and local NLP solvers: a multistart framework for global optimization.
June 22, 2007... The algorithm described here, called OptQuest/NLP or OQNLP, is a heuristic designed to find global optima for pure and mixed integer nonlinear problems with many constraints and variables, where all problem functions are differentiable with...

Power algorithms for inverting Laplace transforms.
June 22, 2007... This paper investigates ways to create algorithms to invert Laplace transforms numerically within a unified framework proposed by Abate and Whitt (2006). That framework approximates the desired function value by a finite linear combination of...

Computing with domino-parity inequalities for the traveling salesman problem (TSP).
June 22, 2007... We describe methods for implementing separation algorithms for domino-parity inequalities for the symmetric traveling salesman problem. These inequalities were introduced by Letchford (2000), who showed that the separation problem can be solved...

An optimization framework for conformal radiation treatment planning.
June 22, 2007... An optimization framework for three-dimensional conformal radiation therapy is presented. In conformal therapy, beams of radiation are applied to a patient from different directions, where the aperture through which the beam is delivered from...

A study on the cross-entropy method for rare-event probability estimation.
June 22, 2007... We discuss the problem of estimating probabilities of rare events in static simulation models using the recently proposed cross-entropy method, which is a type of importance-sampling technique in which the new distributions are successively...

Denser packings obtained in O(n log log n) time.
June 22, 2007... The placement problem is that of packing a set of rectangles into a minimum-area enclosing rectangle. Since it is difficult to optimize directly on a placement, a number of topological representations have been presented in the literature. One...

On a binary-encoded ILP coloring formulation.
June 22, 2007... We further develop the 0/1 ILP formulation of Lee for edge coloring where colors are encoded in binary. With respect to that formulation, our main contributions are (i) an efficient separation algorithm for general block inequalities, (ii) an...

A very large-scale neighborhood search algorithm for the combined through-fleet-assignment model.
June 22, 2007... The fleet-assignment model (FAM) for an airline assigns fleet types to the set of flight legs that satisfies a variety of constraints and minimizes the cost of the assignment. A through connection at a station is a connection between an arrival...

A decomposition and guided simulation methodology for large-scale system design: a study in QoS-capable intranets with fixed and mobile components.(Quality of Service )
June 22, 2007... Integrated design of a large-scale distributed system is challenging due to multiple conflicting design objectives, a large number of stochastic parameters, and a combinatorially large design space. Current approaches using decomposition and...

A two-stage heuristic with ejection pools and generalized ejection chains for the vehicle routing problem with time windows.
June 22, 2007... The vehicle routing problem with time windows (VRPTW) is an important problem in logistics. The problem is to serve a number of customers at minimum cost without violating the customers' time-window constraints or the vehicle-capacity...

Tariff optimization in networks.
June 22, 2007... We consider the problem of determining a set of optimal tariffs for an agent in the network, who owns a subset of all the arcs, and who receives revenue by setting the tariffs on the arcs he owns. Multiple rational clients are active in the...

On the selection of the globally optimal prototype subset for nearest-neighbor classification.
June 22, 2007... The nearest-neighbor classifier has been shown to be a powerful tool for multiclass classification. We explore both theoretical properties and empirical behavior of a variant method, in which the nearest-neighbor rule is applied to a reduced...

Efficient computations for the discrete GI/G/1 system.
June 22, 2007... We consider the discrete-time GI/G/1 system with discrete interarrival times and service-times distributions that have finite supports, and formulate it as a PH/PH/1 system. We then take advantage of the resulting special structure to develop...