Parameters Affecting Cuts

Parameters control the way each class of cuts is used. Those parameters are listed in Table 8.7.

Table 8.7 Parameters for Controlling Cuts

Cut Type 
Interactive Command 
Concert TechnologyLibrary Parameter 
Callable Library Parameter 
Clique 
set mip cuts cliques 
Cliques 
CPX_PARAM_CLIQUES 
Cover 
set mip cuts covers 
Covers 
CPX_PARAM_COVERS 
Disjunctive  
set mip cuts disjunctive 
DisjCuts 
CPX_PARAM_DISJCUTS 
Flow Cover 
set mip cuts flowcuts 
FlowCovers 
CPX_PARAM_FLOWCOVERS 
Flow Path 
set mip cuts pathcut 
FlowPaths 
CPX_PARAM_FLOWPATHS 
Gomory 
set mip cuts gomory 
FracCuts 
CPX_PARAM_FRACCUTS 
GUB Cover 
set mip cuts gubcovers 
GUBCovers 
CPX_PARAM_GUBCOVERS 
Implied Bound 
set mip cuts implied 
ImplBd 
CPX_PARAM_IMPLBD 
Mixed Integer Rounding (MIR) 
set mip cuts mircut 
MIRCuts 
CPX_PARAM_MIRCUTS 

The default value of each of those parameters is 0 (zero). By default, ILOG CPLEX automatically determines how often (if at all) it should try to generate that class of cut. A setting of -1 indicates that no cuts of the class should be generated; a setting of 1 indicates that cuts of the class should be generated moderately; and a setting of 2 indicates that cuts of the class should be generated aggressively. For disjunctive cuts, a setting of 3 is permitted, which indicates that disjunctive cuts should be generated very aggressively.

In the Interactive Optimizer, the command set mip cuts all i applies the value i to all classes of cut parameters. That is, you can set them all at once.

The CutsFactor parameter controls the number of cuts ILOG CPLEX adds to the model. The problem can grow to CutsFactor times the original number of rows in the model (or in the presolved model, if the presolver is active). Thus, a CutsFactor of 1.0 would mean that no cuts will be generated, which may be a more convenient way of turning off all cuts than setting them individually. The default CutsFactor value of 4.0 works well in most cases, as it allows a generous number of cuts while in rare instances it also serves to limit unchecked growth in the problem size.

The AggCutLim parameter controls the number of constraints allowed to be aggregated for generating MIR and flow cover cuts.

The FracPass parameter controls the number of passes for generating Gomory fractional cuts. This parameter will not have any effect if the parameter for set mip cuts gomory has a non-default value.

The FracCand parameter controls the number of variable candidates to be considered for generating Gomory fractional cuts.

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