Originally posted by: Sung_Hwang

I want to know what value will be returned if I use isPrimalFeasible function in unbounded problem.

Let's I have an unbounded model

int check;
cplex.solve();
check = cplex.isPrimalFeasible();

if problem is feasible then IloTrue value will be returned and IloFalse value will be returned.

What if problem is unbounded??

Thank you
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Originally posted by: SystemAdmin

> Sung_Hwang wrote:
> I want to know what value will be returned if I use isPrimalFeasible function in unbounded problem.
>
> Let's I have an unbounded model
>
> int check;
> cplex.solve();
> check = cplex.isPrimalFeasible();
>
> if problem is feasible then IloTrue value will be returned and IloFalse value will be returned.
>
> What if problem is unbounded??

I believe the answer depends on when CPLEX detects unboundedness. If the presolver determines that the problem is unbounded, or if CPLEX starts with the dual simplex algorithm and detects unboundedness before a feasible basis has been found, then isPrimalFeasible will return false. If neither of those happens, and CPLEX detects unboundedness after finding a feasible basis, then isPrimalFeasible will return true. (I have no idea what happens if you try to apply the barrier method to an unbounded problem.)

/Paul

Mathematicians are like Frenchmen: whenever you say something to them, they translate it into their own language, and at once it is something entirely different. (Goethe)
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