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# GRBQConstr

GRBQConstr

  Gurobi quadratic constraint object. Quadratic constraints are always associated with a particular model. You create a quadratic constraint object by adding a quadratic constraint to a model (using `GRBModel.addQConstr`), rather than by using a `GRBQConstr` constructor.

  The methods on quadratic constraint objects are used to get and set constraint attributes. For example, quadratic constraint right-hand sides can be queried by calling `get` (`GRB.DoubleAttr.QCRHS`). Note, however, that it is generally more efficient to query attributes for a set of constraints at once. This is done using the attribute query method on the `GRBModel` object (`GRBModel.get`).

  The full list of attributes can be found in the Attributes section of this document. Examples of how to query and set attributes can also be found in this section.

  char get(GRB.CharAttr attr)
  double get(GRB.DoubleAttr attr)
  int get(GRB.IntAttr attr)
  String get(GRB.StringAttr attr)

    Query the value of a quadratic constraint attribute.

    Arguments:

      attr – The attribute being queried.

    Return value:

      The current value of the requested attribute.

    Example:

          // Get constraint sense
          char sense = constr.get(GRB.CharAttr.QCSense);
          // Get RHS
          double rhs = constr.get(GRB.DoubleAttr.QCRHS);
          // Get information whether constraint participates in a previously computed IIS
          int iisqconstr = constr.get(GRB.IntAttr.IISQConstr);
          // Get constraint name
          String name = constr.get(GRB.StringAttr.QCName);

  void set(GRB.CharAttr attr, char newval)
  void set(GRB.DoubleAttr attr, double newval)
  void set(GRB.IntAttr attr, int newval)
  void set(GRB.StringAttr attr, String newval)

    Set the value of a quadratic constraint attribute.

    Arguments:

      - attr – The attribute being modified.

      - newval – The desired new value of the attribute.

    Example:

          // Set constraint sense
          constr.set(GRB.CharAttr.QCSense, '>');
          // Set RHS
          constr.set(GRB.DoubleAttr.QCRHS, 2.0);
          // Force constraint into IIS
          constr.set(GRB.IntAttr.IISQConstrForce, 1);
          // Set constraint name
          constr.set(GRB.StringAttr.QCName, "newName");

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