All variables eliminated

[rtram]

Hello,

I have been getting the following in my results in some cases on CPLEX for a
linearized version of a quadratic optimization problem.

presolve, constraint flow_balance5[9]:
all variables eliminated, but upper bound = -1 < 0

Please let me know why this would happen in only some cases because this
model is supposed to give me the optimal results. It causes problems on
comparison with an equivalent C program model which gives me the lower
bounds.

Thanks!
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[Paul]

rtram wrote:
> Hello,
>
> I have been getting the following in my results in some cases on CPLEX for a
> linearized version of a quadratic optimization problem.
>
> presolve, constraint flow_balance5[9]:
> all variables eliminated, but upper bound = -1 < 0
>
> Please let me know why this would happen in only some cases because this
> model is supposed to give me the optimal results. It causes problems on
> comparison with an equivalent C program model which gives me the lower
> bounds.
>

For the instances where this happens, the model is infeasible. If you
are confident that the linearized version has to be feasible, then I
would look for an error in the model formulation.

/Paul

[rtram]

Thank you so much. I will check for infeasibility.

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