The empty row is infeasible

[Eefje]

Hey all,

I get an error for a constraint with the name 'two', that says: The empty row two(1) .. 0 = 1 is infeasible, as tolerance the option "Bound_Tolerance" is used with value 1e-008. I get 8 errors from two(1) to two(8).

The program consists of the set nodes. Depots and customers are both subsets of the nodes. Nodes go from 1 to 11,  customers from 1 to 8, and depots from 9 to 11. Nodes are indexed by i_n and j_n, customers by i_c and j_c, and depots by i_d, and j_d.

I have a binary variable x(i_n,j_n). I put only one constraint in the program, to make sure that the problem is not caused by the other constraints.

The constraint 'two' says: sum[i_n, x(i_n,j_c)]=1.

Is there anyone that has any suggestions about what the problem might be? :) Thanks.

Eefje

 

 

[Marcel Hunting]

Hi,

It seems that one of the sets Nodes or customers is empty. It could also be that you are using a domain condition for the variable x that is never satisfied.

If this does not help, could you please add your project here, preferably after adding it to a zip file?

Best regards,

Marcel Hunting

AIMMS Optimization Specialist

[Eefje]

Thanks for your answer. It works if I say that 'nodes' is a subset of Integers. I am not really sure why I need to define this though. Is the set nodes empty if I put 'elementRange(1,11)' in the definition?

Op vrijdag 19 januari 2018 16:44:32 UTC+1 schreef Marcel Hunting:

[Marcel Hunting]

Hi,

The function ElementRange does not require that the set is a subset of Integers. The set nodes should normally not be empty if you use 'elementRange(1,11)' in the definition while nodes is not a subset of Integers. To find out what is going on I would need the project.

Regards,

Marcel

[Eefje]

Okay, thank you. I attached the project.

Op maandag 22 januari 2018 10:14:23 UTC+1 schreef Marcel Hunting:

[Marcel Hunting]

Hi,

Thanks for adding the project. If I replace the definition of the set nodes by ElementRange(1,11) then I get the following error if I (re)open the project: "The element '8' in set "depots" is not in its range set "nodes". This error is correct because the function ElementRange by default pads the numbers with leading zeroes, so the set nodes will contain the elements {'01','02',...,'09','10','11'} and the element '8' is not in that set. If you do not want the numbers to be padded with leading zeroes then you should use the optional 'fill' argument, i.e., ElementRange(1,11,fill:0).

Best regards,

Marcel

[Eefje]

Okay, thank you. This solves the problem

Op vrijdag 26 januari 2018 11:11:58 UTC+1 schreef Marcel Hunting: