Kindervater, G.A.P.
http://repub.eur.nl/ppl/393/
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RePub, Erasmus University RepositoryAirline Revenue Management with Shifting Capacity
http://repub.eur.nl/pub/1074/
Mon, 15 Dec 2003 00:00:01 GMT<div>Pak, K.</div><div>Dekker, R.</div><div>Kindervater, G.A.P.</div>
Airline revenue management is the practice of controlling the booking requests such that the planes are filled with the most profitable passengers. In revenue management the capacities of the business and economy class sections of the plane are traditionally considered to be fixed and distinct capacities. In this paper, we give up this notion and instead consider the use of convertible seats. A row of these seats can be converted from business class seats to economy class seats and vice versa. This offers an airline company the possibility to adjust the capacity configuration of the plane to the demand pattern at hand. We show how to incorporate the shifting capacity opportunity into a dynamic, network-based revenue management model. We also extend the model to include cancellations and overbooking. With a small test case we show that incorporating the shifting capacity opportunity into the revenue management decision indeed provides a means to improve revenues.Finding a feasible solution for a class of distributed problems with a single sum constraint using agents
http://repub.eur.nl/pub/14408/
Tue, 01 Apr 2003 00:00:01 GMT<div>Bruin, A. de</div><div>Kindervater, G.A.P.</div><div>Vredeveld, T.</div><div>Wagelmans, A.P.M.</div>
In this paper, we describe a Multi-Agent System which is capable of finding a feasible solution of a class of distributed problems, in which the subproblems share a single a sum constraint. Emphasis is given to correctness issues and termination detection.Finding a Feasible Solution for a Simple LP Problem using Agents
http://repub.eur.nl/pub/7722/
Wed, 26 May 1999 00:00:01 GMT<div>Bruin, A. de</div><div>Kindervater, G.A.P.</div><div>Vredeveld, T.</div><div>Wagelmans, A.P.M.</div>
In this paper we will describe a Multi-Agent System which is capable of finding a feasible solution of a specially structured linear programming problem. Emphasis is given to correctness issues and termination detection.An object oriented approach to generic branch and bound
http://repub.eur.nl/pub/511/
Mon, 01 Jan 1996 00:00:01 GMT<div>Bruin, A. de</div><div>Kindervater, G.A.P.</div><div>Trienekens, H.W.J.M.</div><div>Goot, R.A. van der</div>
Branch and bound algorithms can be characterized by a small set of basic rules that are applied in a divide-and-conquer-like framework. The framework is about the same in all applications, whereas the specification of the rules is problem dependent. Building a framework is a rather simple task in sequential implementations, but must not be underestimated in the parallel case, especially if an efficient branch and bound algorithm is required. In generic branch and bound models, the basic rules can be clearly identified within the framework, and, hence, it can be developed independently from the application. Furthermore, it gives the user the opportunity to concentrate on the actual problem to be solved, without being distracted by user-irrelevant issues like the properties of the underlying architecture. In this paper, we will discuss an object oriented approach to generic branch and bound. We will show how object orientation can help us to build a flexible branch and bound framework, that is able to perform like any branch and bound algorithm that fits into some powerful taxonomies known from the literature. We will define an interface for the specification of the problem dependent parts, and we will give a first indication of how the user can tune the framework if a non-default behavior is desired.Asynchronous parallel branch and bound and anomalies
http://repub.eur.nl/pub/1438/
Sun, 01 Jan 1995 00:00:01 GMT<div>Bruin, A. de</div><div>Kindervater, G.A.P.</div><div>Trienekens, H.W.J.M.</div>
The parallel execution of branch and bound algorithms can result in seemingly unreasonable speedups or slowdowns. Almost never the speedup is equal to the increase in computing power. For synchronous parallel branch and bound, these effects have been studiedd extensively. For asynchronous parallelizations, only little is known.
In this paper, we derive sufficient conditions to guarantee that an asynchronous parallel
branch and bound algorithm (with elimination by lower bound tests and dominance) will be
at least as fast as its sequential counterpart. The technique used for obtaining the results seems to be more generally applicable.
The essential observations are that, under certain conditions, the parallel algorithm will
always work on at least one node, that is branched from by the sequential algorithm, and
that the parallel algorithm, after elimination of all such nodes, is able to conclude that
the optimal solution has been found.
Finally, some of the theoretical results are brought into connection with a few practical
experiments.Towards an abstract parallel branch and bound machine
http://repub.eur.nl/pub/1439/
Sun, 01 Jan 1995 00:00:01 GMT<div>Bruin, A. de</div><div>Kindervater, G.A.P.</div><div>Trienekens, H.W.J.M.</div>
Many (parallel) branch and bound algorithms look very different from each other at first
glance. They exploit, however, the same underlying computational model. This phenomenon
can be used to define branch and bound algorithms in terms of a set of basic rules that are applied in a specific (predefined) order.
In the sequential case, the specification of Mitten's rules turns out to be sufficient for
the development of branch and bound algorithms. In the parallel case, the situation is a
bit more complicated. We have to consider extra parameters such as work distribution and
knowledge sharing. Here, the implementation of parallel branch and bound algorithms can be
seen as a tuning of the parameters combined with the specification of Mitten's rules.
These observations lead to generic systems, where the user provides the specifications of
the problem to be solved, and the system generates a branch and bound algorithm running on
a specific architecture. We will discuss some proposals that appeared in the literature.
Next, we raise the question whether the proposed models are flexible enough. We analyze
the design decisions to be taken when implementing a parallel branch and bound algorithm.
It results in a classification model, which is validated by checking whether it captures
existing branch and bound implementations.
Finally, we return to the issue of flexibility of existing systems, and propose to add an
abstract machine model to the generic framework. The model defines a virtual parallel
branch and bound machine, within which the design decisions can be expressed in terms of
the abstract machine. We will outline some ideas on which the machine may be based, and
present directions of future work.Local search in physical distribution management
http://repub.eur.nl/pub/1485/
Wed, 01 Jan 1992 00:00:01 GMT<div>Kindervater, G.A.P.</div><div>Savelsbergh, M.W.P.</div>
Physical distribution management presents a variety of decision making problems at three levels of strategic, tactical and operational planning. The importance of effective and efficient distribution management is evident from its associated costs. Physical distribution management at the operational level, which is considered in this paper is responsible for an important fraction of the total distribution costs. Not surprisingly, there is a growing demand for planning systems that produce economical routes. Enormous theoretical as well as practical advances have been made, in the last decade. Some of the resulting vehicle and scheduling models will be discussed in this paper, like vehicle routing problem with time window and the pickup and delivery problem with time window.Sequential and parallel local search for the time-constrained travelling salesman problem
http://repub.eur.nl/pub/1501/
Mon, 01 Jan 1990 00:00:01 GMT<div>Kindervater, G.A.P.</div><div>Lenstra, J.K.</div><div>Savelsbergh, M.W.P.</div>
Local search has proven to be an effective solution approach for the traveling salesman
problem. We consider variants of the TSP in which each city is to be visited within one or
more given time windows. The travel times are symmetric and satisfy the triangle inequality; therobjective is to minimize the tour duration. We develop efficient sequential and parallel algorithms for the verification of local optimality of a tour with respect to <em>k</em>-exchanges.Parallel local search for the time-constrained traveling salesman problem
http://repub.eur.nl/pub/1504/
Sun, 01 Jan 1989 00:00:01 GMT<div>Kindervater, G.A.P.</div><div>Lenstra, J.K.</div><div>Savelsbergh, M.W.P.</div>
In the time-constrained TSP, each city has to be visited within a given time interval.
Such `time windows' often occur in practice. When practical vehicle routing problems are
solved in an interactive setting, one needs algorithms for the time-constrained TSP that
combine a low running time with a high solution quality. Local search seems a natural
approach. It is not obvious, however, how local search for the TSP has to be implemented
so as to handle time windows efficiently. This is particularly true when parallel computer
architectures are available. We consider these questions.Experiments with parallel algorithms for combinatorial problems
http://repub.eur.nl/pub/1512/
Tue, 01 Jan 1985 00:00:01 GMT<div>Kindervater, G.A.P.</div><div>Trienekens, H.W.J.M.</div>
In the last decade many models for parallel computation have been proposed and many
parallel algorithms have been developed. However, few of these models have been realized
and most of these algorithms are supposed to run on idealized, unrealistic parallel machines.
The parallel machines constructed so far all use a simple model of parallel computation.
Therefore, not every existing parallel machine is equally well suited for each type of
algorithm. The adaptation of a certain algorithm to a specific parallel archi- tecture may
severely increase the complexity of the algorithm or severely obscure its essence.
Little is known about the performance of some standard combinatorial algorithms on
existing parallel machines. In this paper we present computational results concerning the
solution of knapsack, shortest paths and change-making problems by branch and bound,
dynamic programming, and divide and conquer algorithms on the ICL-DAP (an SIMD computer),
the Manchester dataflow machine and the CDC-CYBER-205 (a pipeline computer).