Re: [Gurobi] Infeasible model - Help with interpreting the IIS

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Renan Garcia

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Oct 5, 2015, 8:17:49 AM10/5/15
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Constraints R277 and R429 imply that C14 + C166 >= 25000 + 25000 = 50000, but this contradicts constraint R257, which requires that C14 + C166 <= 47945.20547945205. Therefore, the model is infeasible.

On Oct 3, 2015, at 6:01 AM, Martin K <mar...@gmail.com> wrote:

Hi,

I am trying to solve a quite simple MILP with the following structure:
























Once i start adding lower bound to the x_g variables, I get an error saying that the model is infeasible. The IIS shows:

Minimize
 
Subject To
 R257: C14 + C166 <= 47945.20547945205
 R277: - C14 <= -25000
 R429: - C166 <= -25000
Bounds
 C14 free
 C166 free
End

C14 and C166 is the same variable for two time steps. They are suppose to have the lower value 25000. The lower bound A matrix is modelled as diagonal -1 matrix, and the corresponding b vector as (LowerValue*-1) in case of negative lower values.
What is the problem?

Thanks!

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