The rapid development of real-time multimedia applications requires Quality of Service (QoS) based multicast routing in underlying computer networks. The constrained minimum Steiner tree problem in graphs as the underpinning mathematical model is a wellknown NP-complete problem. In this paper we investigate a GRASP (Greedy Randomized Adaptive Search Procedure) approach with VNS (Variable Neighb...

In this paper we consider the classical maximum set packing problem where set cardinality is upper bounded by k. We show how to design a variant of a polynomial-time local search algorithm with performance guarantee (k + 2)/3. This local search algorithm is a special case of a more general procedure that allows to swap up to Θ(log n) elements per iteration. We also design problem instances with...

Protein structure predictions is regarded as a highly challenging problem both for the biology and for the computational communities. Many approaches have been developed in the recent years, moving to increasingly complex lattice models or even off-lattice models. This paper presents a Large Neighborhood Search (LNS) to find the native state for the Hydrophobic-Polar (HP) model on the Face Cent...

We describe the use of very large-scale neighborhood search (VLSN) techniques in examination timetabling problems. We detail three applications of VLSN algorithms that illustrate the versatility and potential of such algorithms in timetabling. The first of these uses cyclic exchange neighborhoods, in which an ordered subset of exams in disjoint time slots are swapped cyclically such that each e...

The Quadratic Assignment Problem (QAP) consists of assigning n facilities to n locations so as to minimize the total weighted cost of interactions between facilities. The QAP arises in many diverse settings, is known to be NP-hard, and can be solved to optimality only for fairly small size instances (typically, n ≤ 25). Neighborhood search algorithms are the most popular heuristic algorithms to...

Local search techniques like simulated annealing and tabu search are based on a neighborhood structure defined on the set of feasible solutions of a discrete optimization problem. For the scheduling problems Pm )I C,,,,, 1 1 prec 1 1 Ui, and a large class of sequencing problems with precedence constraints having local interchange properties we replace a simple neighborhood by a neighborhood on ...

The airline industry has been a pioneer in using operations research techniques to solve complex business problems related to the schedule planning of the airline. Given a flight schedule, an airline’s schedule planning group needs to decide the itinerary of each aircraft and each crewmember so that the total revenue minus the total operating costs is maximum and all the operational constraints...

although several papers have studied no-idle scheduling problems, they all focus on flow shops, assuming one processor at each working stage. but, companies commonly extend to hybrid flow shops by duplicating machines in parallel in stages. this paper considers the problem of scheduling no-idle hybrid flow shops. a mixed integer linear programming model is first developed to mathematically form...