1. Y. Kessaci, N. Melab and E-G. Talbi. An Energy-aware Multi-start Local Search Heuristic for Scheduling VMs on the OpenNebula Cloud Distribution. In Proc. of Intl. Conf. on High Performance Computing & Simulation (HPCS), Spain, Madrid, July 2-6, 2012.

1. I. Chakroun and N. Melab. An Adaptative Multi-GPU based Branch-and-Bound. A Case Study: the Flow-Shop Scheduling Problem. In Proc. of 14th IEEE Intl. Conf. on High Performance Computing and Communications (HPCC'12), UK, Liverpool, June 24-27, 2012.

1. N. Melab, I. Chakroun, M. Mezmaz and D.Tuyttens. A GPU-accelerated Branch-and-Bound Algorithm for the Flow-Shop Scheduling Problem. In Proc. of 14th IEEE Intl. Conf. on Cluster Computing (Cluster'12), China, Beijin, Sept. 24-28, 2012.
2. T-T. Vu, B. Derbel, A. Assim, A. Bendjoudi and N. Melab. Overlay-Centric Load Balancing: Applications to UTS and B&B. In Proc. of 14th IEEE Intl. Conf. on Cluster Computing (Cluster'12), China, Beijin, Sept. 24-28, 2012.

1. M. Mehdi, J-C. Charr, N. Melab, E-G.Talbi and P. Bouvry. A New Cooperative Hybrid Approach Combining Genetic Algorithms and Branch-and-Bound for Solving Permutaion-based Problems. In Proc. of ACM Genetic and Evolutionary Computation Conf. (GECCO’2011), Dublin, Ireland, July 12-16, 2011. Best Paper Award.

1. N. Melab, T-V. Luong, K. Boufaras and E-G. Talbi. Towards ParadisEO-MO-GPU: a Framework for GPU-based Local Search Metaheuristics. Proc. of IWANN’2011, LNCS 6691, Part I, Springer Verlag, 2011.

1. T.V. Luong, L. Loukil, N. Melab and E.-G. Talbi. A GPU-based Iterated Tabu Search for Solving the Quadratic 3-dimensional Assignment Problem. In Proc. of ACS/IEEE AICCSA, Workshop on Parallel Optimization in Emerging Computing Environments (POECE), Hammamet, Tunisia, 2010.
2. T-V. Luong, N. Melab, E-G. Talbi. Large Neighborhood Local Search Optimization on Graphics Processing Units. In Proc. of 23rd IEEE International Parallel & Distributed Processing Symposium (IPDPS), LSPP Workshop, Atlanta, USA, 2010.
3. T-V. Luong, N. Melab and E-G. Talbi. Local Search Algorithms on Graphics Processing Units. A Case Study: the Permutation Perceptron Problem. In LNCS Proc. of 10th European Conf. on Evolutionary Computation in Combinatorial Optimisation (EvoCOP’2010), Istanbul, Turkey, 2010 (nominated for the best paper award).

1. M. Mehdi, J-C. Charr, N. Melab, E-G.Talbi and P. Bouvry. A New Cooperative Hybrid Approach Combining Genetic Algorithms and Branch-and-Bound for Solving Permutaion-based Problems. In Proc. of ACM Genetic and Evolutionary Computation Conf. (GECCO’2009), Dublin, Ireland, July 12-16, 2011. Nominated for the Best Paper Award.
2. Y. Kessaci, N. Melab and E-G. Talbi. A Pareto GA for Green Scheduling of HPC Applications on Distributed Cloud. In proc. of OPTIM/HPCS’2011, Istanbul, July 4-8, 2011.
3. N. Melab, T-V. Luong, K. Boufaras and E-G. Talbi. Towards ParadisEO-MO-GPU: a Framework for GPU-based Local Search Metaheuristics. Proc. of IWANN’2011, LNCS 6691, Part I, Springer Verlag, 2011. Une version étendue a été soumise à Journal of Heuristics.
4. M. Djamaï, B. Derbel and N. Melab. Distributed B&B: A Pure Peer-to-Peer Approach. In Proc. of IEEE IPDPS’2011, Woks. on Large-Scale Parallel Processing (LSPP), May 16-20, Anchorage (Alaska), 2011.
5. A. Bendjoudi, N. Melab and E-G. Talbi. Fault-Tolerant Mechanism for Hierarchical Branch and Bound Algorithm. In Proc. of IEEE IPDPS’2011, Woks. on Large-Scale Parallel Processing (LSPP), May 16-20, Anchorage (Alaska), 2011.
6. T-V. Luong, N. Melab, E-G. Talbi. GPU-based Approaches for Multiobjective Local Search Algorithms. A Case Study: the Flowshop Scheduling Problem. In LNCS proc. of 11th European Conf. on Evolutionary Computation in Combinatorial Optimization (EvoCOP), Torino, Italy, 2011.
7. T-V. Luong, N. Melab, E-G. Talbi. GPU-based Multi-start Local Search Algorithms. In LNCS Proc. of Learning and Intelligent Optimization (LION’5), Rome, Italy, Jan. 17-21 2011.
8. T.V. Luong, N. Melab, E.-G. Talbi. GPU-based Island Model for Evolutionary Algorithms. ACM Genetic and Evolutionary Computation Conference (ACM GECCO’10), Portland, USA, 2010.
9. M. Mehdi, N. Melab, E-G.Talbi and P. Bouvry. Interval-based Initialization Method for Permutation-based Problems. IEEE Congress on Evolutionary Computation (IEEE CEC’10), Barcelona, Spain, 2010.
10. M. Mezmaz, Y.C. Lee, N. Melab, E-G. Talbi and A. Y. Zomaya. A Bi-objective Hybrid Genetic Algorithm to Minimize Energy Consumption and Makespan for Precedence-constrained Applications Using Dynamic Voltage Scaling. IEEE Congress on Evolutionary Computation (IEEE CEC’10), Barcelona, Spain, 2010.
11. T.V. Luong, N. Melab, E.-G. Talbi. GPU-based Parallel Hybrid Evolutionary Algorithms. IEEE Congress on Evolutionary Computation (IEEE CEC’10), Barcelona, Spain, 2010.

12. T.V. Luong, L. Loukil, N. Melab and E.-G. Talbi. A GPU-based Iterated Tabu Search for Solving the Quadratic 3-dimensional Assignment Problem. In Proc. of ACS/IEEE AICCSA, Workshop on Parallel Optimization in Emerging Computing Environments (POECE), Hammamet, Tunisia, 2010. 13. T-V. Luong, N. Melab, E-G. Talbi. Large Neighborhood Local Search Optimization on Graphics Processing Units. In Proc. of 23rd IEEE International Parallel & Distributed Processing Symposium (IPDPS), LSPP Workshop, Atlanta, USA, 2010. 14. T-V. Luong, N. Melab and E-G. Talbi. Local Search Algorithms on Graphics Processing Units. A Case Study: the Permutation Perceptron Problem. In LNCS Proc. of 10th European Conf. on Evolutionary Computation in Combinatorial Optimisation (EvoCOP’2010), Istanbul, Turkey, 2010 (nominated for the best paper award).

1. S. Cahon, N. Melab et E-G. Talbi. ParadisEO : une plate-forme de méta-heuristiques pour l'optimisation mono/multi-objectifs. Dans actes du workshop intl. Logistique et Transport 2006, Hammamet, Tunisie, 30 avr. – 2 mai, 2006.
2. N. Melab, S. Cahon et E-G. Talbi. Optimisation combinatoire sur grilles de calcul pour la fouille de données en spectroscopie PIR. Dans actes du 2ème atelier Extraction et Gestion Parallèles Distribuées de Connaissances (EGPDC’2006) (associé à EGC’2006), Lille, 17 jan. 2006.
3. M. Mezmaz, N. Melab and E-G. Talbi. Optimisation parallèle hybride sur systèmes pair-à-pair. RENPAR'16, Le Croisic, France, Avril 5-8, 2005.
4. S. Cahon, E-G. Talbi et N. Melab. ParadisEO: Un environnement pour le développement d'applications à base de métaheuristiques parallèles coopératives. 5ème congrès de la Société Française de Recherche Opérationnelle et d'Aide à la Décision (ROADEF) Avignon, Mars 2003.
5. S. Cahon, E-G. Talbi et N. Melab. Coopération de métaheuristiques distribuées sur grilles de calcul. Ecole INRIA-CNRS Grid'2002, sur la globalisation des ressources informatiques et des données, Aussois, Décembre 2002.
6. S. Cahon, E-G. Talbi et N. Melab. Coopération de métaheuristiques distribuées sur grilles de calcul. Ecole INRIA-CNRS Grid'2002, sur la globalisation des ressources informatiques et des données Aussois, Décembre 2002.
7. N. Melab, E-G. Talbi, S. Petiton. Contrôle adaptatif du degré de parallélisme : Application à l'algorithme de Gauss-Jordan par blocs. 2e Journées de Recherche sur le Placement dynamique et la Répartition de Charge (JRPRC2), Lille, 19-20 mai 1998.
8. N. Melab, N. Devesa, M.P. Lecouffe, B. Toursel. A multithreaded system for adaptive load balancing in distributed and parallel architectures. Proc. of the 2nd European School of Computer Science (ESPPE'96), Alpe d'Huez, FRANCE, pages 129-132, Apr. 1-5, 1996.

• Colloques internationaux avec comité de lecture et actes

• Colloques nationaux avec comité de lecture et actes

1. S. Cahon, N. Melab et E-G. Talbi. ParadisEO : une plate-forme de méta-heuristiques pour l'optimisation mono/multi-objectifs. Dans actes du workshop intl. Logistique et Transport 2006, Hammamet, Tunisie, 30 avr. – 2 mai, 2006. 2. N. Melab, S. Cahon et E-G. Talbi. Optimisation combinatoire sur grilles de calcul pour la fouille de données en spectroscopie PIR. Dans actes du 2ème atelier Extraction et Gestion Parallèles Distribuées de Connaissances (EGPDC’2006) (associé à EGC’2006), Lille, 17 jan. 2006. 3. M. Mezmaz, N. Melab and E-G. Talbi. Optimisation parallèle hybride sur systèmes pair-à-pair. RENPAR'16, Le Croisic, France, Avril 5-8, 2005.

S. Cahon, E-G. Talbi et N. Melab. ParadisEO: Un environnement pour le développement d'applications à base de métaheuristiques parallèles coopératives. 5ème congrès de la Société Française de Recherche Opérationnelle et d'Aide à la Décision (ROADEF) Avignon, Mars 2003.

o S. Cahon, E-G. Talbi et N. Melab. Coopération de métaheuristiques distribuées sur grilles de calcul. Ecole INRIA-CNRS Grid'2002, sur la globalisation des ressources informatiques et des données, Aussois, Décembre 2002.

  S. Cahon, E-G. Talbi et N. Melab. Coopération de métaheuristiques distribuées sur grilles de calcul. Ecole INRIA-CNRS Grid'2002, sur la globalisation des ressources informatiques et des données Aussois, Décembre 2002.

N. Melab, E-G. Talbi, S. Petiton. Contrôle adaptatif du degré de parallélisme : Application à l'algorithme de Gauss-Jordan par blocs. 2e Journées de Recherche sur le Placement dynamique et la Répartition de Charge (JRPRC2), Lille, 19-20 mai 1998.

N. Melab, N. Devesa, M.P. Lecouffe, B. Toursel. A multithreaded system for adaptive load balancing in distributed and parallel architectures. Proc. of the 2nd European School of Computer Science (ESPPE'96), Alpe d'Huez, FRANCE, pages 129-132, Apr. 1-5, 1996.

1. L. Brunie, M. Miquel, J-M. Pierson, A. Tchounikine, C. Dhaenens, N. Melab, E-G. Talbi, A. Hameurlain, F. Morvan. Information grids: managing and mining semantic data in a grid infrastructure; open issues and application to geno-medical data. In Proc. of IEEE DEXA'03, pages 509-518, Czech Republic, Prague, Sept. 2003.
2. S. Cahon, E-G. Talbi and N. Melab. ParaDisEO: a Framework for Parallel and Distributed Biologically Inspired Metaheuristics. In Proc. (CDROM, 9 pages) of IEEE NIDISC'03 (In conjunction with IEEE IPDPS'03), Nice, France, April 2003.
3. Nordine Melab, Sébastien Cahon, El-Ghazali Talbi and Ludovic Duponchel. Parallel GA-based Wrapper Feature Selection for Spectroscopic Data Mining. IEEE Intl. Workshop on Bio-Inspired Solutions to Parallel Processing Problems (BioSP3), Fort Lauderdale, Florida, USA, Apr. 15-19, 2002.
4. N. Melab, L. Deruelle, M. Bouneffa and H. Basson. Towards a Changeability Assessment of Distributed Multi-language Software Code. 7th IEEE Intl. Workshop on Empirical Studies of Software Maintenance (WESS'01), Florence, Italy, Nov. 9, 2001.
5. L. Deruelle, M. Bouneffa, N. Melab and H. Basson. Analysis and Manipulation of Distributed Multi-Language Software Code. In Proc. of the IEEE Intl. Workshop on Source Code Analysis and Manipulation (IEEE-SCAM'2001), Florence, Italy, Nov 2001.
6. L. Deruelle, M. Bouneffa, N. Melab and H. Basson. A Change propagation Model and Platform for Multi-Database Applications. In Proc of the IEEE Intl. Conf. on Software Maintenance (IEEE-ICSM'2001), Florence, Italy, Nov 2001.
7. L. Deruelle, N. Melab, M. Bouneffa and H. Basson. Web Site Evolution based on Change Impact Analysis. In Proc. of ISE'2001, Las Vegas, USA, June 2001.
8. Nordine Melab and El-Ghazali Talbi. A Parallel Genetic Algorithm for Rule Mining. IEEE Intl. Workshop on Bio-Inspired Solutions to Parallel Processing Problems (BioSP3), San Francisco, USA, Apr. 23, 2001.
9. N. Melab, M. Bouneffa, L. Deruelle and H. Basson. Change Propagation in Multi-language Distributed Software. Proc. of PDCS'2000, pages 472-477, Las Vegas, Nevada, USA, Aug. 8-10, 2000.
10. N. Melab and L. Deruelle. Toward a Model and a Platform for Profiling of Multi-language Distributed Object Software. Proc. of PDCS'2000, pages 275-280, Las Vegas, Nevada, USA, Aug. 8-10, 2000.
11. N. Melab, L. Deruelle, M. Bouneffa and H. Basson. Instrumentation-based Profiling Techniques. Proc. of ISCA-CATA'2000, New Orleans, Louisiana, USA, Mar.29-31, 2000.
12. N. Melab, H. Basson, M. Bouneffa, and L. Deruelle. Performance of Object-oriented Code: Profiling and Instrumentation. In the Proc. of the IEEE Intl. Conf. on Software Maintenance (IEEE-ICSM'99), Oxford, UK., Aug. 30 - Sep. 3, 1999.
13. N. Melab, E-G. Talbi and S. Petiton. A Parallel Adaptive version of the Block-based Gauss-Jordan Algorithm. Proc. of IEEE-IPPS/SPDP99 (13th Intl. Parallel Processing Symp. & 10th Symp. on Parallel and Distributed Processing), pages 350-355, San Juan, Puerto Rico, Apr. 12-16, 1999.
14. N. Melab, N. Devesa, M.P. Lecouffe, B. Toursel. Increasing the Granularity of Parallelism in the P3 Parallel Evaluation Scheme of Functional Languages. Proc. of the 10th ISCA Intl. Conf. on Parallel and Distributed Computing Systems, PDCS'97, New Orleans, Louisiana, USA, pages 578-583, Oct. 1-3, 1997.
15. N. Melab, N. Devesa, M.P. Lecouffe, B. Toursel. A Periodic Adaptive Strategy for Monitoring Distributed Applications: Description and Analysis. Proc. of the 11th Intl. Symposium on High Performance Computing Systems, HPCS'97, Winnipeg, Manitoba, Canada, pages 645-654, July. 10-12, 1997.
16. N. Melab, N. Devesa, M.P. Lecouffe, B. Toursel. Adaptive Load Balancing and Multithreading. Proc. of the 9th ISCA Intl. Conf. on Parallel and Distributed Computing Systems, PDCS'96, Dijon, FRANCE, pages 343-348, Volume 1, Sep. 25-27, 1996.
17. N. Melab, N. Devesa, M.P. Lecouffe, B. Toursel. Adaptive load balancing of irregular applications. A case study: IDA* applied to the 15-puzzle problem. Springer Verlag, LNCS 1117, Proc. of the Third Intl. Workshop, IRREGULAR'96, pages 327-338, Santa Barbara, California, USA, Aug. 19-21, 1996.
18. N. Melab, N. Devesa, M.P. Lecouffe, B. Toursel. An adaptive Load Information Collection Policy. Proc. of the Int. Conf. on Parallel and Distributed Processing Techniques and Applications (PDPTA'96), Sunnyvale, California, USA, pages 649-658, Aug. 9-11, 1996.
19. N. Melab, N. Devesa, M.P. Lecouffe, B. Toursel. An Adaptive Load Balancing Algorithm with a Multithreaded Implementation. Proc. of the 11th Int. Conf. on Systems Engineering (ICSE'96), Las Vegas, Nevada, USA, pages 97-102, Jul. 9-11, 1996.

1. M. Mehdi, N. Melab, E-G.Talbi and P. Bouvry. Interval Island Model Initialization for Permutation-based Problems. Poster in ACM Genetic and Evolutionary Computation Conf. (GECCO’2009), Montreal, Canada, July 2009.
2. L. Loukil, M. Mehdi, N. Melab, E-G Talbi, and P. Bouvry. A Parallel Hybrid Genetic Algorithm - Simulated Annealing for Solving Q3AP on Computational Grid. In Proc. of the 22th IEEE Intl. Parallel and Distributed Processing Symposium (IPDPS’2009), NIDISC Workshop. Roma, Italy, 2009.
3. J. Tavares, A-A. Tantar, N. Melab and E-G. Talbi. The Influence of Mutation on Protein-Ligand Docking Optimization: a Locality Analysis. In Proc. of the 10th Intl. Conf. on Parallel Problem Solving from Nature (PPSN 2008), LNCS 5199, Springer Verlag, Pages 589-598, 2008.
4. M. Mehdi, M. Mezmaz, N. Melab, E-G.Talbi and P. Bouvry. An Efficient Hybrid P2P Approach for Non-redundant Tree Exploration in B&B Algorithms. In IEEE Proc. of Intl. Workshop on P2P, Parallel, Grid and Internet Computing (In conj. with CISIS'08), Pages 354-359, Barcelona, Spain, March 2008.
5. J. Tavares, A-A. Tantar, N. Melab and E-G. Talbi. The Impact of Local Search on Protein-Ligand Docking Optimization. In IEEE Proc. of the 8th Intl. Conf. on Pon Hybrid Intelligent Systems (HIS 2008), Pages 53-58, Barcelona, Spain, Sept. 10-12, 2008.
6. B. Parent, A. Tantar, N. Melab, E-G. Talbi, D. Horvath. Grid-based evolutionary strategies applied to the conformational sampling problem. In Proc. of IEEE Congress on Evolutionary Computation, 2007 (CEC2007), pages 291-296, Singapore, 25-28 Sept. 2007.
7. I. Zunino, N. Melab and E-G. Talbi. A Grid-enabled Framework for Exact Optimization Algorithms. In Proc. of 2007 High Performance Computing and Simulation Conference (HPC&S), Prague, Czech Republic, June 4-6, 2007.
8. A. Bendjoudi, N. Melab and E-G. Talbi. Parallel Brand-and-Bound Algorithm on a Peer-to-Peer System. In Proc. of 7th IEEE Intl. Workshop on Global and Peer-to-Peer Computing (In conj. with IEEE CCGRID’2007), Rio de Janeiro, Brazil , May 14-17, 2007.
9. M. Mezmaz, N. Melab and E-G. Talbi. A Grid-enabled Branch and Bound Algorithm for Solving Challenging Combinatorial Optimization Problems. In Proc. of 21th IEEE Intl. Parallel and Distributed Processing Symp. (IPDPS), Long Beach, California, March 26th-30th, 2007. (Selection rate: 26%).
10. A-A. Tantar, N. Melab and E-G. Talbi. A Comparative Study of Parallel Metaheuristics for Protein Structure Prediction on the Computational Grid. In Proc. of the 10th IEEE Intl. Workshop on Nature Inspired Distributed Computing (NIDISC’07 - in conjunction with IPDPS’2007), Long Beach, California, March 26th, 2007.
11. M. Mezmaz, N. Melab and E-G. Talbi. A Grid-based Parallel Approach of the Multi-Objective Branch and Bound. In Proc. of the 15th IEEE Euromicro Conf. on Parallel, Distributed and Network-based Processing, Naples, Italy, Feb. 7-9, 2007.
12. M. Mehdi, M. Mezmaz, N. Melab and E-G. Talbi. Toward a Napster-like P2P B&B Algorithm and Island Models for Parallel Multi-objective Optimization on the Computational Grid. In Proc. of the 2007 High Performance Computing and Simulation Conference (HPC&S 2007), Prague, Czech Republic. June 4-6, 2007.
13. M. Mezmaz, N. Melab and E-G. Talbi. Using the Multi-Start and Island Models for Parallel Multi-objective Optimization on the Computational Grid. In Proc. of IEEE Intl. Workshop on Biologically-inspired Optimization Methods for Parallel and Distributed Architectures (in conjunction with the 2nd IEEE Intl. Conf. on e-Science and Grid Computing), Amsterdam, The Netherlands, Dec. 4-6, 2006.
14. N. Melab, M. Mezmaz, E-G. Talbi and B. Wei. Parallel Peer-to-Peer Multi-objective Optimization using the Multi-Start Model. In Proc. of the IFIP Intl. Conf. on Network and Parallel Computing (NPC’2006), Pages 20-26, Tokyo 2-4 Oct. 2006.
15. A. Tantar, N. Melab, E-G. Talbi and B. Toursel. Solving the Protein Folding Problem with a Bicriterion Genetic Algorithm on the Grid. 4th IEEE Intl. Workshop on Biomedical Computations on the Grid (BioGrid'06 – In conj. with IEEE CCGRID’06), Pages 43-, Singapore, May 16-19, 2006.
16. S. Cahon, E-G. Talbi and N. Melab. A Parallel and Hybrid Multi-Objective Evolutionary Algorithm applied to the Design of Cellular Networks. In Proc. of MELECON’2006, Benalmádena (Málaga), Spain, May 16-19, 2006.
17. M. Mezmaz, N. Melab, E-G. Talbi. A Grid Exact Hybrid Approach for Solving Multi-Objective Problems. In Proc. of 9th IEEE Intl. Workshop on Nature Inspired Distributed Computing (NIDISC’06 - in conjunction with IPDPS’2006), Rhodes Island, Greece, Apr. 25-29, 2006.
18. S. Cahon, N. Melab, E-G Talbi. An Enabling Framework for Parallel Optimization on the Computational Grid. In the Proc. of the 5th IEEE Intl. Symposium on Cluster Computing and the Grid (CCGRID’2005), Cardiff, UK, 9-12 May, 2005.
19. J-M. Pierson, L. Brunie, C. Dhaenens, A. Hameurlain, N. Melab, M. Miquel, F. Morvan, E-G. Talbi and A. Tchounikine. Grid for Geno-Medicine: A Glimpse on the GGM Project. In the Proc. of the 3rd IEEE Intl. Workshop on Biomedical Computations on the Grid (BioGrid’2005 – in conjunction with CCGRID’2005), Cardiff, UK, 9-12 May, 2005.
20. N. Melab, M. Mezmaz and E-G. Talbi. Parallel Hybrid Multi-objective Island Model in Peer-to-Peer Environment. In the Proc. of the 8th IEEE Intl. Workshop on Nature Inspired Distributed Computing (NIDISC’05 - in conjunction with IPDPS’2005), Denver, Colorado, Apr. 4-8, 2005.
21. F. Cappello, F. Desprez, M. Dayde, E. Jeannot, Y. Jégou, S. Lanteri, N. Melab, R. Namyst, P. Primet, O. Richard, E. Caron, J. Leduc, G. Mornet. Grid'5000: a large scale, reconfigurable, controlable and monitorable Grid platform. In 6th IEEE/ACM Intl .Workshop on Grid Computing - GRID 2005, Seattle, Washington, USA, Nov. 13-14, 2005.
22. M. Mezmaz, N. Melab and E-G. Talbi. Towards a Coordination Model for Parallel Cooperative P2P Multi-objective Optimization. In Springer Verlag LNCS 3470, Proc. of European Grid Conf. (EGC’2005), pages 305-314, Amsterdam, The Netherlands, 14-16 Feb. 2005 (taux de selection : 39%).
23. S. Cahon, N. Melab, E-G Talbi and M. Schoenauer. ParadisEO-based Design of Parallel and Distributed Evolutionary Algorithms. In Proc. of Evolutionary Algorithms EA'03, Marseille, France, October 2003. Revised Selected Paper for Springer Verlag LNCS 2936, pages 216-228, 2004.