ILOG CPLEX 11.0 User's Manual

the conflict to arrive at a minimal conflict. A conflict smaller than the full model may makeit easier for the user to analyze the source of infeasibilities in the original model.If the model happens to contain multiple independent causes of infeasibility, it may benecessary for the user to repair one cause and then repeat the process with a furtherrefinement.What a Conflict Is NotInformation about the necessary magnitude of change to data values, in order to gainfeasibility, is not available from a conflict. The algorithms for detecting and refiningconflicts do their work by including or removing a constraint or bound in trial solutions, notby varying the data of those entities. For that kind of insight, or for an approach to automaticrepair of infeasibility, the FeasOpt feature, discussed in Repairing Infeasibilities withFeasOpt on page 409, is more appropriate.ILOG CPLEX refines conflicts only among the constraints and bounds in your model. Itdisregards the objective function while it is refining a conflict. In particular, if you have set aMIP cutoff value with the idea that the cutoff value will render your model infeasible, andthen you apply the conflict refiner, you will not achieve the effect you expect. In such a case,you should add one or more explicit constraints to enforce the restriction you have in mind.In other words, add constraints rather than attempt to enforce a restriction through theseparameters:●●●CutLo or CutUp in Concert Technology (not recommended to enforce infeasibility)CPX_PARAM_CUTLO or CPX_PARAM_CUTUP in the Callable Library (notrecommended to enforce infeasibility)mip tolerance lowercutoff or uppercutoff in the Interactive Optimizer (notrecommended to enforce infeasibility)392 ILOG CPLEX 11.0 — USER’ S MANUAL