ILOG CPLEX 11.0 User's Manual

Then display the objective value of each solution in the Interactive Optimizer with thiscommand:display solution list *Afterwards, you see that all solutions in the pool are of a cost less than or equal to 548; thatis, within 10% of the optimal objective value of 499.Example: Few or Many Solutions through Intensity ParameterUse the solution pool intensity parameter (SolnPoolIntensity,CPX_PARAM_SOLNPOOLINTENSITY) to balance the number of solutions generated and theamount of time or memory consumed. Lower intensity values generate fewer solutions,whereas higher intensity values generate more solutions.If you need many solutions, but do not want to impair performance too greatly, the value 2(moderate) is a good choice for most models.For example, the following session in the Interactive Optimizer reads a model in LP formatof the Example: Simple Facility Location Problem on page 302.The session then effectivelyremoves the stopping criterion of the populate limit parameter by setting it very high.read location.lpset mip limits populate 10000set mip pool intensity 2set mip pool relgap 0.1populateYou can see from the log that setting the pool intensity to 2 yields results faster than whenpopulate is called after MIP optimization at the default value of solution pool intensity.If you set the solution pool intensity parameter to 3 (aggressive) or 4 (very aggressive), thenan even larger number of solutions will be produced.At solution pool intensity 2, a large number of solutions are produced (in this case, 196solutions, though the precise number of solutions may vary on your platform).If you set solution pool intensity at 3 instead, populate will generate a greater number ofsolutions (in this case, 208 solutions).Likewise, if you set solution pool intensity at 4 instead, a very great number of solutions willbe produced and stored in the solution pool, as this setting exhaustively enumeratessolutions.In this small example, the settings 3 and 4 happen to produce the same number of solutions(208), but in general it will not be the case that the two settings have the same effect.322 ILOG CPLEX 11.0 — USER’ S MANUAL