ILOG CPLEX 11.0 User's Manual

How to Invoke the Conflict RefinerTable 26.1 summarizes the methods and routines that invoke the conflict refiner, dependingon the component or API that you choose.Table 26.1 Conflict RefinerAPI or Component Invoke Conflict Refiner Access Results Save ResultsConcert Technology for C++ Users IloCplex::refineConflict getConflict writeConflictConcert Technology for Java Users IloCplex.refineConflict getConflict writeConflictConcert Technology for .NET Users Cplex.RefineConflict GetConflict WriteConflictCallable LibraryCPXrefineconflictCPXrefineconflictextCPXgetconflictCPXgetconflictextCPXclpwriteInteractive Optimizer conflict display conflict all write file.clpThe following sections explain more about these methods and routines.How a Conflict Differs from an IISIn some ways a conflict resembles an irreducibly inconsistent set (IIS). Detection of an IISamong the constraints of a model is a standard methodology in the published literature; anIIS finder has long been available as a tool within ILOG CPLEX. Both tools (conflict refinerand IIS finder) attempt to identify an infeasible subproblem of a provably infeasible model.However, a conflict is more general than an IIS. The IIS finder is applicable only tocontinuous LP models, whereas the conflict refiner is capable of doing its work on any typeof problem, including mixed integer models or models containing quadratic elements.Also, you can specify one or more groups of constraints for a conflict; a group will either bepresent together in the conflict, or else will not be part of it at all.You can also assign numeric preference to a constraint or to groups of constraints. In thecase of an infeasible model that has more than one possible conflict, the preferences youassign will guide the tool toward detecting the conflict you want. Preferences allow you tospecify aspects of the model that may otherwise be difficult to encode.While the conflict refiner usually will deliver a smaller set of constraints to consider than theIIS finder will, the methods are different enough that the reverse can sometimes be true. Thefact that the IIS finder implements a standard methodology may weigh toward its use insome situations. Otherwise, the conflict refiner can be thought of as usually doing everythingILOG CPLEX 11.0 — USER’ S MANUAL 393