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SDN simplifies network management by relying on declarativity (high-level interface) and expressiveness (network flexibility). We propose a solution to support those features while preserving high robustness and scalability as needed in carrier-grade networks. Our solution is based on (i) a two-layer architecture separating connectivity and optimization… (More)

Deviation is a recent constraint to balance a set of variables with respect to a given mean. We show that the propagators recently introduced are not bound-consistent when the mean is rational. We introduce bound-consistent propagators running in linear time with respect to the number of variables. We evaluate the improvement in terms of efficiency and… (More)

This paper introduces DEVIATION, a soft global constraint to obtain balanced solutions. A violation measure of the perfect balance can be defined as the Lp norm of the vector variables minus their mean. SPREAD constraints the sum of square deviations to the mean [5, 7] i.e. the L2 norm. The L1 norm is considered here. Neither criterion subsumes the other… (More)

This paper considers the daily assignment of newborn infant patients to nurses in a hospital. The objective is to balance the workload of the nurses, while satisfying a variety of side constraints. Prior work proposed a MIP model for this problem, which unfortunately did not scale to large instances and only approximated the objective function, since… (More)

Many assignment problems require the solution to be balanced. Such a problem is the Balanced Academic Curriculum Problem (BACP) [1]. Standard deviation is a common way to measure the balance of a set of values. A recent constraint presented by Pesant and Régin [2] enforces the mean µ and the standard deviation σ of a set of variables. Our work extends [2]… (More)

- Pierre Schaus, Yves Crama Hec, Belgium Ulg, Van Roy Peter, Ingi, Belgium Olivier Uclouvain +1 other
- 2009

This work could not have been achieved without the support of the following persons. My parents who encourage me to finish this thesis (even by coming in Providence). They are great example for their five children. My wife Caro who supports me everyday. She's always there to remind me what is the most important in my life and helps me to find a good balance… (More)

The Steel Mill Slab Problem is an optimization benchmark that has been studied for a long time in the constraint-programming community but was only solved efficiently in the two last years. Gargani and Refalo solved the problem using Large Neighborhood Search and Van Henten-ryck and Michel made use of constraint programming with an improved symmetry… (More)

The Balanced Academic Curriculum Problem (BACP) has received little attention in Constraint Programming. Only a few articles deals with this problem with experimental results on the three small instances publicly available in CSPLIB. The present article describes an approach to efficiently solve this challenging problem. Optimal solutions are produced on a… (More)

Large neighborhood search (LNS) [25] is a framework that combines the expressiveness of constraint programming with the efficiency of local search to solve combinatorial optimization problems. This paper introduces an extension of LNS, called multi-objective LNS (MO-LNS), to solve multi-objective combi-natorial optimization problems ubiquitous in practice.… (More)

The Large Neighborhood Search (LNS) approach for solving Constrained Optimization Problems has been proved to be effective on a wide range of problems. LNS is a local search metaheuristic that uses a complete search method (such as CP) to explore a large neighborhood. At each step, the neighborhood is defined by relaxing a subset, called fragment, of the… (More)