ILOG CPLEX 11.0 User's Manual

●●CPX_PARAM_TILIM in the Callable Librarytimelimit in the Interactive Optimizer3. Call the optimizer again.Remember to leave the advanced indicator parameter at its default value of 1 (one) so thatthe polishing will proceed from the advanced start.●●AdvInd in Concert TechnologyCPX_PARAM_ADVIND in the Callable Library● advance in the Interactive OptimizerAs with the RINS heuristic, the subMIP node-limit parameter also controls aspects of thework that solution polishing performs.●●SubMIPNodeLim in Concert TechnologyCPX_PARAM_SUBMIPNODELIM in the Callable Library● mip limits submipnodelim in the Interactive OptimizerSolution polishing always requires the presence of a feasible solution from which to start. Ifthe feasible solution came from a MIP start, it must be consistent with any dual presolvereductions that ILOG CPLEX makes. Therefore, in order for polishing to work on a MIPstart, you may need to disable some combination of dual presolve reductions, nonlinearpresolve reductions, or symmetry reductions. For details about the parameters to disablethose features, see the ILOG CPLEX Parameter Reference Manual, especially these pages:◆◆the presolve switch: PreInd (bool), CPX_PARAM_PREIND (int)the linear reduction switch: PreLinear, CPX_PARAM_PRELINEAR◆ the symmetry breaking parameter: Symmetry, CPX_PARAM_SYMMETRYSolution polishing is much more time-intensive than any of the other heuristics, but canyield better solutions in some situations.Preprocessing: Presolver and AggregatorWhen you invoke the MIP optimizer, whether through the Interactive Optimizer commandmipopt, through a call to the Concert Technology IloCplex method solve, or through theCallable Library routine CPXmipopt, ILOG CPLEX by default automatically preprocessesyour problem. Table 14.10 summarizes the preprocessing parameters. In preprocessing,ILOG CPLEX applies its presolver and aggregator one or more times to reduce the size ofthe integer program in order to strengthen the initial linear relaxation and to decrease theoverall size of the mixed integer program.ILOG CPLEX 11.0 — USER’ S MANUAL 277