Originally posted by: lisaz

Hello, 

I have a problem with one constraint in my model. 

Including this constraint, CPLEX gives no solution. Although, the problem is really small and should be easy to solve. (I first want to make sure the model works with a small dataset before solving a much bigger problem.) 

I attached the whole model + data. 

Constraint 3 is the problem: 

//Cons03: no two flights are assigned to the same gate at the same time
Cons03: forall(f in Flights) forall(j in Flights) forall(g in Gates)
assignment[f][g]*assignment[j][g]*(End[f]-Start[j])*(End[j]-Start[f]) <= 0;

Without this constraint CPLEX is able to solve my problem but I don't know what's the problem. I also don't get an error message regarding the formulation of the constraint.

Thanks in advance for your help! I really appreciate it. 

Lisa 

Originally posted by: PhilippeLaborie

The engine says that the problem is infeasible.

And I think it is because in your constraint Cons03, you post the constraint even when f and j are the same flight.

I think you should better post something like:

forall(f in Flights, j in Flights: f<j) {

  forall(g in Gates) {

    assignment[f][g]*assignment[j][g]*(End[f]-Start[j])*(End[j]-Start[f]) <= 0;

  }
}
 

Originally posted by: lisaz

It works in my model. Thanks so much for your help!! :)