VBasis/CBasis get and set

Answered

Thomas Schlechte

• February 21, 2023 10:26
• Edited

I am a little confused that when getting the LP basis in python, you have to

self.model.getAttr("VBasis", self.model.getVars())

but for setting you have to do something like this:

        for var in self.model.getVars():
            var.setAttr("VBasis", vBasis[var.index])

Am I right or did I just not found the corresponding method?

Wouldn't it be good to have also a Wrapper like:

 model.setAttr("VBasis",..)

Thanks a lot

Thomas

Related to

• Attribute
• Warm Start

1

• 

  Marika Karbstein

  Gurobi Staff

  • February 21, 2023 13:00

  Hi Thomas,

  The function Model.setAttr() already exists.

  Cheers,
  Marika

  -1
• 

  Thomas Schlechte

  • February 21, 2023 14:19
  • Edited

  

  

  

  Hi Marika,

  ah okay, I did not see the call with 3 arguments. So it should work like this

  // solve
  ...
  vBasis = self.model.getAttr("VBasis", self.model.getVars())
  cBasis = self.model.getAttr("CBasis", self.model.getConstrs())
  
  // do for example a problem specific RENS 
  ...
  
  // set lp solution
  self.model.setAttr("VBasis", model.getVars(), vBasis)
  self.model.setAttr("CBasis", model.getConstr(), cBasis)

  Thanks

  Thomas

   

  1
• 

  noah smith

  • June 19, 2024 05:45

  

  

  Hi, Thomas's second comment here is very useful. Could highly recommend that his code-snippet, or something like it, be included in discussions of lp warm start. A simple 'hello world style' example model doing this would also be useful. Multiple examples of warm start would be helpful.

  Concrete 'how to' with examples that pop up when googling 'gurobi warm start'.

  Understood this stuff is apparently totally obvious for gurobi employees.

  It's not for every gurobi user, have learned that the hard way over the last few days.

  Thanks

  Noah

   

  0
• 

  Gwyneth Butera

  Gurobi Staff

  • June 19, 2024 11:45

  Thanks for the suggestion Noah! I have added this to my list of potential improvements for the Knowledge Base. -G

  1

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