Can I get the inverse of an LP basis from a GUROBI model object in Python API?

Ongoing

Botan Citil

• August 03, 2022 20:03

I am solving L1 regression which has the following generic LP model.

\[\begin{aligned}
& \underset{\beta, z^+\geq0,z^-\geq0}{\min}
& & \sum_{i=1}^n  z^+_i+z^-_i \\
& \text{s.t.}
& & \left\langle \beta, (1,\mathbf{x}_i)\right\rangle+z^+_i-z^-_i = \mathbf{y}_i, \;\; i=1,\ldots,n.\\
\end{aligned}\]

Is it possible to get the inverse of the basis of this model once the model is solved?

For example, I can get the names of the variables that are in the basis with the following code. I am looking for something similar to the following code.

gurobiBasisVarNames=[]
for variable in model.getVars():
    if variable.VBasis == 0:
        gurobiBasisVarNames.append(variable.VarName)

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• 

  Matthias Miltenberger

  Gurobi Staff

  • August 04, 2022 10:52

  No, the inverse of the basis matrix is not available, unfortunately.

  Best regards,
  Matthias

  1
• 

  Matthias Miltenberger

  Gurobi Staff

  • August 05, 2022 09:42

  SO crosspost: linear programming - Can I get the inverse of an LP basis from a GUROBI model object in Python API? - Stack Overflow

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  Botan Citil

  • August 05, 2022 21:22

  

  

  

  Thank you for responding. I will indicate if my question is cross-posted somewhere else next time I post a question.

  I have two follow-up questions, please let me know if I should ask them separately.

  1. Is there a function equivalent to GRBBinvcolj() from the C API for the Python API?
  2. If an equivalent function to GRBBinvcolj()  is not available for Python, what can I do? Do you have examples of Gurobi C API functions being used inside a Python code?

   

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