Mincost is infeasible or unbounded


Hello everyone, this is my error message.

Warning: After zero iterations the preprocessor of CPLEX 20.1 concluded that MinCost is infeasible or unbounded.

I think the problems lays in my constraints.

Production_workcenter is 100% incorrect but i’m not sure how to use the subset allowed_product_per_workcenter

Are there other problems ?

Thank you




Best answer by Marcel Hunting 4 May 2022, 17:29

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4 replies

Userlevel 5
Badge +4

Hi @solam. Your model appears to be unbounded, that is, some of the X(i,w,t) or Tr(i,m,l,t) can become very negative. You can check this by (temporarily) adding the following constraint:

TotalCost >= -100000000

If you then solve the model TotalCost will become -100000000.

You declared both variables X and Tr as free variables, so having range (-inf,inf). Are you sure these variables should not be nonnegative?


Hi Marcel, thank you for answering that fast. Nice catch theses variables should be nonnegative. Now the problem is, the solution is said to be infeasible.

Do you know why ? I’m sure my production capacity constraint is wrong but don’t know how to make it work.


Userlevel 5
Badge +6

Complementing @Marcel Hunting, Inv should be nonnegative too. 


With the 3 decision variables nonnegative I was able to run without infeasibilities. Do you have a new scenario? 

And, looking on Production_capacity(w,t), I advise you to use units. For that, you will need create a Quantity with the units you will use on the project, then set on the parameter, variable and contraint ‘unit’ part, example: 

Then, if there is a unit problem with your constraint, AIMMS will give you an error. 


Hope that helps. 


Yes, I was able to run the program. Thank your for your help!


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