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Adding stochasticity to a MIP model- Constraint problem

  • 20 August 2020
  • 2 replies
  • 65 views

Hi there,

I am trying to add stochasticity to a deterministic MIP model and I am receiving the following message:

The empty row em.Stochastic([M,L,L,L],(B),(B)) .. 0 <= -39688691.0796 is infeasible, as tolerance the option "Bound_Tolerance" is used with value 1e-08.

This constraint is:

index= (i,j) - at the error message (B) is i and (B) is j;

definition sum((k,t), Flow(k,i ,j ,t)) <= sum((e,t),EmissionProfile(e,t))

EmissionProfile is the parameter with the scneario tree and Flow is the stochastic variable. Worth to mention the deterministic model is running with no issues

 I appreciate any light on this topic or how to debug it.

Thanks and best regards,

Denis

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Best answer by Chris Kuip 22 August 2020, 14:21

Hello Dfraga,

 

From what you share, I note:

  • A negative RHS. During generation, AIMMS will move the value of fixed/frozen variables to the RHS. Can you check whether there are any fixed/frozen flow variables, perhaps because t is an index in a Horizon?
  • Usually, there is no flow when the from and the to are the same. So I do not understand why a constraint is generated. Can you check the index domain condition on the constraint "em?

Perhaps the above questions help you find the answer.

 

With kind regards,

 

Chris.

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2 replies

Userlevel 3

Hello Dfraga,

 

From what you share, I note:

  • A negative RHS. During generation, AIMMS will move the value of fixed/frozen variables to the RHS. Can you check whether there are any fixed/frozen flow variables, perhaps because t is an index in a Horizon?
  • Usually, there is no flow when the from and the to are the same. So I do not understand why a constraint is generated. Can you check the index domain condition on the constraint "em?

Perhaps the above questions help you find the answer.

 

With kind regards,

 

Chris.

Thanks, Chris. The questions indeed helped in finding the error. The model is up and running now. 

Best regards,

Denis

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