It is common for the introduction of new business requirements to lead to unexpected results during the model refinement process. For example, a new constraint might make a model infeasible or a solution might no longer make sense after an additional objective has been enabled.

The ILOG OPL-CPLEX Development System has several features to help model developers find and address the problems that arise in the real world:

• Conflict detection and display–Constraints can be grouped with or without relaxation priorities. When encountering infeasibility during the solve process, ILOG OPL automatically invokes ILOG CPLEX's Conflict Refiner to find and display the constraint, group of constraints or variable bounds that are causing the infeasibility.

View the demo (opens a new window).



• Recommended relaxations–The model relaxation recommendation engine suggests changes to variable bounds or constraint limits to make an infeasible model feasible.
• Model Generation–Before solving, ILOG OPL-CPLEX will analyze the model during expansion and identify, for example, unused decision variables, data elements and constraints. These warnings assist with error detection in the model formulations.

A warning is presented when constraints are not expanded. Enlarge image (opens a new window).



• Run configuration–This feature allows you to combine a model with multiple data sets for execution, providing a convenient method for testing the model's behavior across data instances without having to resort to writing ILOG Script or coding. If a specific model and data combination provides unexpected results, it is possible to drill down even further using the Problem Browser, the Conflict Refiner, or the Recommended Relaxations features.
• Execution tracing–The ILOG OPL-CPLEX Development System provides full access to the ILOG CPLEX log file, so users can track solve progress. Users can utilize a wide range of integrated development environment (IDE) features–from pause and continue, to exporting intermediate data to a flat file for detailed analysis, to using ILOG Script to insert breaks–to manage the model review process.