ILOG CPLEX 11.0 User's Manual

Optimizer correspond exactly to routines of the Component Libraries, so anomalies due tothe ILOG CPLEX-part of your application will manifest themselves in the InteractiveOptimizer as well, and contrariwise, if the Interactive Optimizer behaves appropriately onyour problem, you can be reasonably sure that routines you call in your application from theComponent Libraries work in the same appropriate way.With respect to parameter settings, you can write a parameter file with the file extension.prm from your application by means of one of these methods:◆◆◆◆IloCplex::writeParam in the C++ APIIloCplex.writeParam in the Java APICplex.WriteParam in the .NET APICPXwriteparam in the Callable Library◆ write file.prm in the Interactive OptimizerThe Interactive Optimizer can read a .prm file and then set parameters exactly as they are inyour application.In the other direction, you can use the display command in the Interactive Optimizer toshow the nondefault parameter settings; you can then save those settings in a .prm file forre-use later. See the topic Saving a Parameter Specification File on page 18 in the referencemanual of the Interactive Optimizer for more detail about using a parameter file in this way.To use the Interactive Optimizer for debugging, you first need to write a version of theproblem from the application into a formatted file that can then be loaded into the InteractiveOptimizer. To do so, insert a call to the method IloCplex::exportModel or to the routineCPXwriteprob into your application. Use that call to create a file, whether an LP, SAV, orMPS formatted problem file. (Understanding File Formats on page 144 briefly describesthese file formats.) Then read that file into the Interactive Optimizer and optimize theproblem there.Note that MPS, LP and SAV files have differences that influence how to interpret the resultsof the Interactive Optimizer for debugging. SAV files contain the exact binary representationof the problem as it appears in your program, while MPS and LP files are text filescontaining possibly less precision for numeric data. And, unless every variable appears onthe objective function, ILOG CPLEX will probably order the variables differently when itreads the problem from an LP file than from an MPS or SAV file. With this in mind, SAVfiles are the most useful for debugging using the Interactive Optimizer, followed by MPSfiles, then finally LP files, in terms of the change in behavior you might see by use of explicitfiles. On the other hand, LP files are often quite helpful when you want to examine theproblem, more so than as input for the Interactive Optimizer. Furthermore, try solving boththe SAV and MPS files of the same problem using the Interactive Optimizer. Differentresults may provide additional insight into the source of the difficulty. In particular, use thefollowing guidelines with respect to reproducing your program’s behavior in the InteractiveOptimizer.ILOG CPLEX 11.0 — USER’ S MANUAL 139