Results 1  10
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22
J.P.: Counterexamples in probabilistic model checking
 In: Tools and Algorithms for the Construction and Analysis of Systems (TACAS), 13th International Conference. (2007
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Finding the k shortest hyperpaths
"... The K shortest paths problem has been extensively studied for many years. Efficient methods have been devised, and many practical applications are known. Shortest hyperpath models have been proposed for several problems in different areas, for example in relation with routing in dynamic networks. Ho ..."
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Cited by 17 (4 self)
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The K shortest paths problem has been extensively studied for many years. Efficient methods have been devised, and many practical applications are known. Shortest hyperpath models have been proposed for several problems in different areas, for example in relation with routing in dynamic networks. However, the K shortest hyperpaths problem has not yet been investigated. In this paper we present procedures for finding the K shortest hyperpaths in a directed hypergraph. This is done by extending existing algorithms for K shortest loopless paths. Computational experiments on the proposed procedures are performed, and applications in transportation, planning and combinatorial optimization are discussed.
Provisioning virtual private networks under traffic uncertainty
 Networks
, 2004
"... We investigate a network design problem under traffic uncertainty which arises when provisioning Virtual Private Networks (VPNs): given a set of terminals that must communicate with one another, and a set of possible traffic matrices, sufficient capacity has to be reserved on the links of the large ..."
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Cited by 11 (0 self)
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We investigate a network design problem under traffic uncertainty which arises when provisioning Virtual Private Networks (VPNs): given a set of terminals that must communicate with one another, and a set of possible traffic matrices, sufficient capacity has to be reserved on the links of the large underlying public network so as to support all possible traffic matrices while minimizing the total reservation cost. The problem admits several variants depending on the desired topology of the reserved links, and the nature of the traffic data uncertainty. We present compact linear mixedinteger programming formulations for the problem with the classical hose traffic model and for a new, less conservative, robust variant relying on the traffic statistics that are often available. These flowbased formulations allow to solve optimally mediumtolargesize instances with commercial MIP solvers. We also propose a combined branchandprice and cutting plane algorithm to tackle larger instances. Computational results obtained for several classes of instances are reported and discussed. Key words: Virtual private networks, network design, traffic uncertainty, robust optimization, linear mixedinteger programs, branchandprice, cutting planes. 1
From machine translation to computer assisted translation using finitestate models
 In Proceedings of the 2004 Conference on Empirical Methods in Natural Language Processing (EMNLP04
, 2004
"... Stateoftheart machine translation techniques are still far from producing high quality translations. This drawback leads us to introduce an alternative approach to the translation problem that brings human expertise into the machine translation scenario. In this framework, namely Computer Assiste ..."
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Cited by 9 (4 self)
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Stateoftheart machine translation techniques are still far from producing high quality translations. This drawback leads us to introduce an alternative approach to the translation problem that brings human expertise into the machine translation scenario. In this framework, namely Computer Assisted Translation (CAT), human translators interact with a translation system, as an assistance tool, that dinamically offers, a list of translations that best completes the part of the sentence already translated. In this paper, finite state transducers are presented as a candidate technology in the CAT paradigm. The appropriateness of this technique is evaluated on a printer manual corpus and results from preliminary experiments confirm that human translators would reduce to less than 25 % the amount of work to be done for the same task. 1
NeAT: a toolbox for the analysis of biological networks, clusters, classes and pathways
 Nucleic Acids Res
, 2008
"... classes and pathways ..."
A lazy version of eppstein’s k shortest paths algorithm
 In: WEA
, 2003
"... Abstract. We consider the problem ofenumerating, in order ofincreasing length, the K shortest paths between a given pair ofnodes in a weighted digraph G with n nodes and m arcs. To solve this problem, Eppstein’s algorithm first computes the shortest path tree and then builds a graph D(G) representin ..."
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Cited by 5 (0 self)
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Abstract. We consider the problem ofenumerating, in order ofincreasing length, the K shortest paths between a given pair ofnodes in a weighted digraph G with n nodes and m arcs. To solve this problem, Eppstein’s algorithm first computes the shortest path tree and then builds a graph D(G) representing all possible deviations from the shortest path. Building D(G) takesO(m+n log n) time in the basic version ofthe algorithm. Once it has been built, the K shortest paths can be obtained in order ofincreasing length in O(K log K) time. However, experimental results show that the time required to build D(G) is considerable, thereby reducing the practical interest ofthe algorithm. In this paper, we propose a modified version ofEppstein’s algorithm in which only the parts of D(G) which are necessary for the selection of the K shortest paths are built. This version maintains Eppstein’s worstcase running time and entails an important improvement in practical performance, according to experimental results that are also reported here. 1
Handling CFMU slots in busy airports
 Proceedings of the Air Traffic Management R&D Seminar
, 2003
"... In busy airports, too many departing flights take off out of the time slot required by the Central Flow Management Unit (CFMU). During ground traffic peaks, taxi out times and runway queuing delays increase, and it seems very hard and maybe unfeasible for ground controllers to organise properly the ..."
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Cited by 3 (2 self)
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In busy airports, too many departing flights take off out of the time slot required by the Central Flow Management Unit (CFMU). During ground traffic peaks, taxi out times and runway queuing delays increase, and it seems very hard and maybe unfeasible for ground controllers to organise properly the traffic so that aircraft take off at their scheduled time. In a first part, this paper shows how a ground traffic simulator that includes a conflict resolution module can give accurate predictions of takeoff times. Then, different strategies taking into account these predictions so as to incorporate CFMU slot constraints are compared. The deviation between the required slots and the final takeoff times is measured. The efficiency of the different strategies is compared by the correlation between the number of aircraft and the generated delay. 1
CNOP: a package for constrained network optimization
 IN PROC. 3RD INT. WORKSHOP ON ALGORITHM ENGINEERING AND EXPERIMENTS (ALENEX 01), LNCS 2153
, 2001
"... We present a generic package for resource constrained network optimization problems. We illustrate the flexibility and the use of our package by solving four applications: route planning, curve approximation, minimum cost reliability constrained spanning trees and the table layout problem. ..."
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Cited by 3 (0 self)
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We present a generic package for resource constrained network optimization problems. We illustrate the flexibility and the use of our package by solving four applications: route planning, curve approximation, minimum cost reliability constrained spanning trees and the table layout problem.
On the crossing numbers of complete graphs
 University of Waterloo
, 2006
"... I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii In this thesis we prove two main results. The Triangle ..."
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Cited by 2 (1 self)
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I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii In this thesis we prove two main results. The Triangle Conjecture asserts that the convex hull of any optimal rectilinear drawing of Kn must be a triangle (for n � 3). We prove that, for the larger class of pseudolinear drawings, the outer face must be a triangle. The other main result is the next step toward Guy’s Conjecture that the crossing number of Kn is 1
K : A heuristic search algorithm for finding the k shortest paths
 Artificial Intelligence
"... We present a directed search algorithm, called K ∗ , for finding the k shortest paths between a designated pair of vertices in a given directed weighted graph. K ∗ has two advantages compared to current kshortestpaths algorithms. First, K ∗ operates onthefly, which means that it does not require ..."
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Cited by 2 (1 self)
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We present a directed search algorithm, called K ∗ , for finding the k shortest paths between a designated pair of vertices in a given directed weighted graph. K ∗ has two advantages compared to current kshortestpaths algorithms. First, K ∗ operates onthefly, which means that it does not require the graph to be explicitly available and stored in main memory. Portions of the graph will be generated as needed. Second, K ∗ can be guided using heuristic functions. We prove the correctness of K ∗ and determine its asymptotic worstcase complexity when using a consistent heuristic to be the same as the state of the art, O(m + n log n + k), with respect to both runtime and space, where n is the number of vertices and m is the number of edges of the graph. We present an experimental evaluation of K ∗ by applying it to route planning problems as well as counterexample generation for stochastic model checking. The experimental results illustrate that due to the use of heuristic, onthefly search K ∗ can use less time and memory compared to the most efficient kshortestpaths algorithms known so far. Key words: kshortestpaths problem; K ∗ ; heuristic search; onthefly search 1.