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# MIPDUALREDUCTIONS

Description | Branch and Bound: Limits operations that can reduce the MIP solution space.
Type | Integer
Topic area | Presolve
Values |
0 | Prevent all dual reductions.
1 | Allow all dual reductions.
2 | Allow dual reductions on continuous variables only.
Default value | 1
Notes | The MIPDUALREDUCTIONS control, when set to a value different from 1 will adjust the values of other controls in order to prevent MIP solver operations that can result in the removal of dominated solutions. For example, dual reductions during preprocessing attempts to remove dominated solutions based on objective arguments, assuming that all constraints are known to the Optimizer. If a problem is detected to have symmetries, the solver might also remove some symmetrical solutions from the search space. In both cases, the set of feasible MIP solutions might be reduced. With default settings, it is only guaranteed that at least one optimal solution remains. When attempting to collect the n-best solutions, it is recommended to set MIPDUALREDUCTIONS=2. This will ensure that the only solutions missed by the enumeration are those that only differ from an existing solution in the values of the continuous variables. Setting MIPDUALREDUCTIONS=0 disables all dual reductions. This is recommended for advanced use cases such as optimization under external constraints applied dynamically to the problem using callbacks. In this case, MIPDUALREDUCTIONS=0 guarantees that any solution to the original problem that satisfies all of the user's external constraints maps to a feasible solution in the presolved space.
Affects routines | XPRSmipoptimize ( MIPOPTIMIZE).
See also | MIPPRESOLVE, PRECOMPONENTS, PRESOLVEOPS, SYMMETRY.
Category | Control

Parent Topic Control Parameters

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