ILOG CPLEX 11.0 User's Manual

eginning and yet pay off with shorter overall runtime. When you are tuning performance, itis usually because the model is difficult, and then probing is worth trying.At the default setting of the Probe parameter (0 (zero)), ILOG CPLEX will automaticallydecide an appropriate level of probing. Setting the Probe parameter to 1, 2, or 3, results inincreasing levels of probing to be performed beyond the default level of probing. A setting of-1 results in no probing being performed.To activate an increasing level of probing:◆ In the Interactive Optimizer, use the command set mip strategy probe i.◆◆In Concert Technology, set the integer parameter Probe.In the Callable Library, set the integer parameter CPX_PARAM_PROBE.CutsCuts are constraints added to a model to restrict (cut away) noninteger solutions that wouldotherwise be solutions of the continuous relaxation. The addition of cuts usually reduces thenumber of branches needed to solve a MIP.In the following descriptions of cuts, the term subproblem includes the root node (that is, theroot relaxation). Cuts are most frequently seen at the root node, but they may be added byILOG CPLEX at other nodes as conditions warrant.ILOG CPLEX generates its cuts in such a way that they are valid for all subproblems, evenwhen they are discovered during analysis of a particular subproblem. If the solution to asubproblem violates one of the subsequent cuts, ILOG CPLEX may add a constraint toreflect this condition.◆ Clique Cuts on page 272◆ Cover Cuts on page 272◆ Disjunctive Cuts on page 272◆ Flow Cover Cuts on page 272◆ Flow Path Cuts on page 272◆ Gomory Fractional Cuts on page 272◆ Generalized Upper Bound (GUB) Cover Cuts on page 273◆ Implied Bound Cuts on page 273◆ Mixed Integer Rounding (MIR) Cuts on page 273◆ Adding Cuts and Re-Optimizing on page 273◆ Counting Cuts on page 273ILOG CPLEX 11.0 — USER’ S MANUAL 271