ILOG CPLEX 11.0 User's Manual

should be assigned higher priority than the second group. In that way, you can use priority toachieve better solutions.Setting priority based on the magnitude of objective coefficients is also sometimes helpful.You can specify priority for any variable, though the priority is used only if the variable is ageneral integer variable, a binary integer variable, a semi-continuous variable, a semi-integervariable, or a member of a special ordered set. To specify priority, use one of the followingroutines or methods:◆From the Callable Library, use CPXcopyorder to copy a priority order and apply it, orCPXreadcopyorder to read the copy order from a file in ORD format. That format isdocumented in the reference manual ILOG CPLEX File Formats.◆ From Concert Technology, use the method setPriority to set the priority of a givenvariable or setPriorities to set priorities for an array of variables. Use the methodreadOrder to read priorities from a file in ORD format and apply them.ILOG CPLEX can generate a priority order automatically, based on problem-datacharacteristics. This facility can be activated by setting the MIPOrdType parameter to one ofthe values in Table 14.12.Table 14.12Parameters for Branching Priority OrderParameterBranching Priority Order0 no automatic priority order will be generated (default)1 decreasing cost coefficients among the variables2 increasing bound range among the variables3 increasing cost per matrix coefficient count among the variablesIf you explicitly read a file of priority orders, its settings will override any generic priorityorder you may have set by this parameter.The parameter MIPOrdInd, when set to 0 (zero), allows you to direct ILOG CPLEX toignore a priority order that was previously read from a file. The default setting for thisparameter means that a priority order will be used, if one has been read in.Using the MIP SolutionThis section discusses the optimal solution or the best feasible solution, if no optimum hasbeen proved. For information about managing the entire pool of feasible solutions, seeSolution Pool: Generating and Keeping Multiple Solutions on page 301.ILOG CPLEX 11.0 — USER’ S MANUAL 281