Get bounds from the computed IIS

回答済み

John Daudu

• 2024年11月21日 10:08

Hi there, 
I am trying to solve a nsp problem. For an infeasible model, I have computed the IIS. The logs show a constraint and two bounds (that I had manually set) that violate the constraint. Reading the docs on GRBcomputeIIS, I understand that removing a bound or a constraint will make the model feasible. The constraint has to stay, I'd like to know if I can get the variable bounds computed by the IIS in gurobipy and proceed to remove the bound.

\ Model NurseSchedulingModel_copy
\ LP format - for model browsing. Use MPS format to capture full model detail.
Maximize multi-objectives
  OBJ0: Priority=0 Weight=1 AbsTol=1e-06 RelTol=0
  
  Preferences: Priority=1 Weight=1 AbsTol=1e-06 RelTol=0
   2 x[17,1,11] + 2 x[17,2,10]
  Fairness: Priority=2 Weight=-1 AbsTol=1e-06 RelTol=0
  
Subject To
 c_forbidden_consecutive_shift[17,2,10]: x[17,2,10] = 1 -> x[17,1,11] = 0
Bounds
 x[17,1,11] = 1
 x[17,2,10] = 1
Binaries
 x[17,1,11] x[17,2,10]
End

関連

• Attribute
• Infeasible

0

• 

  Matthias Miltenberger

  Gurobi Staff

  • 2024年11月21日 10:30

  Hi John,

  You can query the IIS results by checking the variables attributes IISLB and IISUB.

  I hope that answers your question.

  Cheers,
  Matthias

  0
• 

  John Daudu

  • 2024年11月21日 22:16

  

  

  

  Hi Matthias, 
  
  I appreciate the prompt response. IISLB and IISUB are the attributes I needed. 
  
  Thank you! 

  0

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