We propose a model for the integrated optimization of vehicle rotations and vehicle compositions in long distance railway passenger transport. The main contribution of the paper is a hypergraph model that is able to handle the challenging technical requirements as well as very general stipulations with respect to the “regularity” of a schedule. The hypergraph model directly generalizes network ...

We discuss the problem of constructing physician schedules in emergency rooms. Starting from practical instances encountered in six different hospitals of the Montreal (Canada) area, we first we propose generic forms for the constraints encountered in this context. We then review several possible solution techniques that can be applied to physician scheduling problems, namely tabu search, colum...

Kuznetsov independence of variables X and Y means that, for any pair of bounded functions f(X) and g(Y ), E [f(X)g(Y )] = E [f(X)] E [g(Y )], where E [·] denotes interval-valued expectation and denotes interval multiplication. We present properties of Kuznetsov independence for several variables, and connect it with other concepts of independence in the literature; in particular we show that st...

In a conventional PBS, each crewmember sends in his bid (i.e. preferences) without knowing the preferences of other crewmembers. He is bidding "blind". As a consequence, conflicts result: some trips are desired by (i.e. fulfill the preferences of) too many crewmembers and some are desired by no crewmembers. In the post-bid optimization process, the global optimizer attempts to reconcile conflic...

This article provides an overview of the performance and the theoretical complexity of approximate and exact methods for various versions of the shortest path problem. The proposed study aims to improve the resolution of a more general covering problem within a column generation scheme in which the shortest path problem is the sub-problem.

At an airport a series of assignment problems need to be solved before aircraft can arrive and depart and passengers can embark and disembark. A lot of different parties are involved with this, each of which having to plan their own schedule. Two of the assignment problems that the ’Regie’ at Amsterdam Airport Schiphol (AAS) is responsible for, are the gate assignment problem (i.e. where to pla...

Combinatorial optimization games form an important subclass of cooperative games. In recent years, increased attention has been given to the issue of finding good cost shares for such games. In this paper, we define a very general class of games, called integer minimization games, which includes the combinatorial optimization games in the literature as special cases. We then present new techniq...

We study the problem of computing the minimum volume enclosing ellipsoid containing a given point set S = {p1, p2, . . . , pn} ⊆ R. Using “core sets” and a column generation approach, we develop a (1 + )-approximation algorithm. We prove the existence of a core set X ⊆ S of size at most |X| = α = O ( d ( log d + 1 )) . We describe an algorithm that computes the set X and a (1 + )-approximation ...

The task of an elevator control is to schedule the elevators of a group such that small waiting and travel times for the passengers are obtained. We present an exact reoptimization algorithm for this problem. A reoptimization algorithm computes a new schedule for the elevator group each time a new passenger arrives. Our algorithm uses column generation techniques and is, to the best of our know...

Given a set of entities associated with points in Euclidean space, minimum sum-of-squares clustering (MSSC) consist in partitioning this set into clusters such that the sum of squared distances from each point to the centroid of its cluster is minimized. A column generation algorithm for MSSC was given in du Merle et al. [15]. The bottleneck of that algorithm is resolution of the auxiliary prob...