CPLEX 约束的逻辑值

Question

A C++ CPLEX model that I have is long, and I build constraints inside functions. Say I have a function that returns a constraint:

IloConstraint f(IloInt i, IloInt j, IloNumVarArray x)
{
    IloConstraint constr;
    constr = (x[j]-x[i] >= 15)  && (x[j]-x[i] <= 20);
    return constr;
}

Is it possible to do pass a constant array instead of a variable array x , and to obtain a logical value of constraint, ie to do something like.

IloNumArray a(env, 5, 1, 1, 1, 1, 1);
IloConstraint c = f(1,2,a);
cout<<c.logicalValue();

Answer 1

You can use IloAnd

In CPLEX documentation you can read

For example, you may write:

 IloAnd and(env);
 and.add(constraint1);
 and.add(constraint2);
 and.add(constraint3);
 

Those lines are equivalent to :

 IloAnd and = constraint1 && constraint2 && constraint3;

Answer 2

I couldn't find a real solution, but I have some workaround. Assuming we already have a constraint c , we create a new model with c as its constraint, and add new bounds for the variables.

bool constraintLogicalValue(IloConstraint const& constr, IloNumVarArray const& x, IloNumArray const& a, unsigned int const n)
{        
    IloEnv env;
    IloModel model(env);
    IloCplex cplex_model(model);
    cplex_model.setOut(env.getNullStream());

    for(int i=0; i<n; ++i)
        model.add(x[i]==a[i]);

    model.add(constr);
    return(cplex_model.solve());
}

Now we can use it in the following way:

int n;
IloEnv env;
IloModel model(env);
IloNumVarArray x (env);
...
IloNumArray a(env);
for(int i=0; i<n; ++i)
    a.add(1);

IloConstraint c = f(1,2,x);
cout<<constraintLogicalValue(c, env, x, a, n);

EDIT: A problem could be an existing bounds for x , which are passed into constraintLogicalValue() . If x[i]==a[i] is out of these bonds, for some i , the model is unfeasible and we obtain false as a result, event if constr is satisfied.

Sometimes this is what we want.