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Cardinality Reasoning for bin-packing constraint. Application to a tank allocation problem

TitleCardinality Reasoning for bin-packing constraint. Application to a tank allocation problem
Publication TypeConference Paper
Year of Publication2012
AuthorsSchaus, Pierre, Régin Jean-Charles, Schaeren Rowan Van, Dullaert Wout, and Raa Birger
Conference NameCP2012: 18th International Conference on Principles and Practice of Constraint Programming, Québec City, Canada

Flow reasoning has been successfully used in CP for more than a decade. It was originally introduced by R ́egin in the well-known Alldifferent and Global Cardinality Constraint (GCC) available in most of the CP solvers. The BinPacking constraint was introduced by Shaw and mainly uses an independent knapsack reasoning in each bin to filter the possible bins for each item. This paper considers the use of a cardinal- ity/flow reasoning for improving the filtering of a bin-packing constraint. The idea is to use a GCC as a redundant constraint to the BinPacking that will count the number of items placed in each bin. The cardinality variables of the GCC are then dynamically updated during the propaga- tion. The cardinality reasoning of the redundant GCC makes deductions that the bin-packing constraint cannot see since the placement of all items into every bin is considered at once rather than for each bin in- dividually. This is particularly well suited when a minimum loading in each bin is specified in advance. We apply this idea on a Tank Allocation Problem (TAP). We detail our CP model and give experimental results on a real-life instance demonstrating the added value of the cardinality reasoning for the bin-packing constraint.

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