ObjNAbsTol

Type: double
Modifiable: Yes

This attribute is used to set the allowable degradation for objective <span>$</span>n<span>$</span> when doing hierarchical multi-objective optimization. You set <span>$</span>n<span>$</span> using the ObjNumber parameter.

Hierarchical multi-objective MIP optimization will optimize for the different objectives in the model one at a time, in priority order. If it achieves objective value <span>$</span>z<span>$</span> when it optimizes for this objective, then subsequent steps are allowed to degrade this value by at most ObjNAbsTol.

Objective degradations are handled differently for multi-objective LP models. For LP models, solution quality for higher-priority objectives is maintained by fixing some variables to their values in previous optimal solutions. These fixings are decided using variable reduced costs. The value of the ObjNAbsTol parameter indicates the amount by which a fixed variable's reduced cost is allowed to violate dual feasibility. The value of the related ObjNRelTol attribute is ignored.

The default absolute tolerance for an objective is 0.

The number of objectives in the model can be queried (or modified) using the NumObj attribute.

Please refer to the discussion of Multiple Objectives for more information on the use of alternative objectives.

For examples of how to query or modify attributes, refer to our Attribute Examples.

Try Gurobi for Free

Choose the evaluation license that fits you best, and start working with our Expert Team for technical guidance and support.

Evaluation License
Get a free, full-featured license of the Gurobi Optimizer to experience the performance, support, benchmarking and tuning services we provide as part of our product offering.
Academic License
Gurobi supports the teaching and use of optimization within academic institutions. We offer free, full-featured copies of Gurobi for use in class, and for research.
Cloud Trial

Request free trial hours, so you can see how quickly and easily a model can be solved on the cloud.

Search