Gurobi Constraints value print

[sandy]

Hello Everyone ,

I have written an optimization model using JAVA with gurobi. it has several thousand constraints in the model. Is it possible  to print below.

1) All Constraints value after optimization in some file.

2) All constraints with value which did not satisfy in case of infeasible solution.

Appreciate if anyone could help.

Thanks in advance.

[Renan Garcia]

1) All Constraints value after optimization in some file.

You can infer this by querying for the Slack constraint attribute (see http://www.gurobi.com/documentation/7.0/refman/slack.html#attr:Slack). For general guidance on querying for attributes in Java, refer to http://www.gurobi.com/documentation/7.0/refman/java_attribute_examples.html#JavaAttributeExamples.

Another approach would be to use the GRBExpr.getValue() method (see http://www.gurobi.com/documentation/7.0/refman/java_grbexpr_getvalue.html) if you've saved off the expressions for the constraints.

2) All constraints with value which did not satisfy in case of infeasible solution.

Try the GRBModel.computeIIS() method (see http://www.gurobi.com/documentation/7.0/refman/java_grbmodel_computeiis.html) to find an irreducible inconsistent subsystem.

[sandy]

Thanks Renan for answering . for GRBExpr.getValue() , do i need to put constraint name or whole expression inside brackets , I tried constraint but it is giving error. and also i read documentation and could not find any syntax example. 

[Kostja Siefen]

Hi Sandy,

The getValue() function does not have any parameter. It computes the value of the expression from the latest optimal solution available. Thus, it will throw an error if no solution is available.

Kostja