C++ Attribute Examples
Consider the case where you have a Gurobi model m. You can
retrieve the number of variables in the model by querying the
NumVars model attribute
using the
get method:
cols = m.get(GRB_IntAttr_NumVars);
If you've performed optimization on the model, the optimal objective value can be obtained by querying the ObjVal model attribute:
obj = m.get(GRB_DoubleAttr_ObjVal);
If you'd like to query the value that a variable takes in the computed solution, you can query the X attribute for the corresponding variable object:
vars = m.getVars()
for (int j = 0; j < cols; j++)
xj = vars[j].get(GRB_DoubleAttr_X)
You can also query the value of X for multiple variables in a single
get call
on the model m:
double xvals[] = m.get(GRB_DoubleAttr_X, m.GetVars()))
For each attribute query method, there's an analogous set routine.
To set the upper bound of a variable, for example:
v = m.getVars()[0] v.set(GRB_DoubleAttr_UB, 0)(In this example, we've set the upper bound for the first variable in the model to 0).