The AllDifferent Constraint with Precedences. We propose AllDiffPrec, a new global constraint that combines together an AllDifferent constraint with precedence constraints that strictly order given pairs of variables. We identify a number of applications for this global constraint including instruction scheduling and symmetry breaking. We give an efficient propagation algorithm that enforces bounds consistency on this global constraint. We show how to implement this propagator using a decomposition that extends the bounds consistency enforcing decomposition proposed for the AllDifferent constraint. Finally, we prove that enforcing domain consistency on this global constraint is NP-hard in general.
References in zbMATH (referenced in 2 articles )
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- Fages, Jean-Guillaume; Lapègue, Tanguy: Filtering AtMostNValue with difference constraints: application to the shift minimisation personnel task scheduling problem (2014)
- Bessiere, Christian; Narodytska, Nina; Quimper, Claude-Guy; Walsh, Toby: The AllDifferent constraint with precedences (2011)