### Infeasible model with fixed feasible solution

Posted:

**Sat Mar 23, 2019 11:08 pm**Hi,

I am having trouble with my model, as it appears to be integer infeasible (CPLEX error 1217), even when I fix the binary variable x(i,j,m) for specific links to 1, establishing a feasible solution. This model is a MILP formulation of a time dependent VRP, where the goal is to minimize the total time of all routes by choosing the best time interval m for each link (i,j).

I have analysed all the equations back and forth and they seem correct, I don't understand why the model isn't working. The presolver says:

"Bound infeasibility column x(3.1.2)"

I don't understand what this means. Also, in the equation listing, for Eq5(3,1,1):

Eq5(3,1,1).. t(1) - t(3) - 500000000*x(3,1,1) =E= -499998691 ;

(LHS = -500000000, INFES = 1309 ****)

Shouldn't t(1) =1309? Because x(3,1,1) and t(3) are already fixed in the formulation, so I don't understand why does t(1) not respect the equation.

I will attach the model and the input files. There are descriptions throughout the depot to make it easier to understand

Any help would be much appreciated! Thank you in advance,

Manuel

I am having trouble with my model, as it appears to be integer infeasible (CPLEX error 1217), even when I fix the binary variable x(i,j,m) for specific links to 1, establishing a feasible solution. This model is a MILP formulation of a time dependent VRP, where the goal is to minimize the total time of all routes by choosing the best time interval m for each link (i,j).

I have analysed all the equations back and forth and they seem correct, I don't understand why the model isn't working. The presolver says:

"Bound infeasibility column x(3.1.2)"

I don't understand what this means. Also, in the equation listing, for Eq5(3,1,1):

Eq5(3,1,1).. t(1) - t(3) - 500000000*x(3,1,1) =E= -499998691 ;

(LHS = -500000000, INFES = 1309 ****)

Shouldn't t(1) =1309? Because x(3,1,1) and t(3) are already fixed in the formulation, so I don't understand why does t(1) not respect the equation.

I will attach the model and the input files. There are descriptions throughout the depot to make it easier to understand

Any help would be much appreciated! Thank you in advance,

Manuel