ILOG CPLEX 11.0 User's Manual

An attempt to display or access a conflict when none exists, whether because the conflictrefiner has not yet been invoked or because an error occurred, results in this error message:No conflict exists.The cause of those messages will usually be apparent to a user. However, numeric instabilitymay cause genuine uncertainty for a user. In an unstable model, one of the optimizers mayreturn a valid conclusion of infeasibility, based on the numeric precision allowed by themodel, and yet when a trivial modification is made, the model status changes, and a feasiblesolution now seems attainable. Because one of the conventional indicators of instability canbe this switching back and forth from feasibility to infeasibility, the user should be alert tothis possibility. The conflict refiner will halt and return an error code if an infeasible modelsuddenly appears feasible during its analysis, due to this presumption of numeric instability.The user should turn attention away from infeasibility analysis at that point, and toward thesections in this manual such as Numeric Difficulties on page 185.Using the Conflict Refiner in an ApplicationHere is an example using the conflict refiner in the C++ API of Concert Technology. Youwill modify one of the standard examples ilomipex2.cpp distributed with the product.Starting from that example, locate this statement in it:cplex.solve();ILOG CPLEX 11.0 — USER’ S MANUAL 403