Retrive attribute Pi

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Benedicte Rimmereid

• April 06, 2024 08:36

I have a pure linear model, but I cannot retrieve the dual value (Pi). Are there any common reasons why this might happen? See my code below, for it only tries to retrieve the dual values in the case of optimality.

# Open a file named "sensitivity_analysis.txt" in write mode

if lp_model.status == GRB.INFEASIBLE:

  # handle infeasibility

  pass

elif lp_model.status == GRB.OPTIMAL:

  # handle optimality

    with open("sensitivity_analysis.txt", "w") as file:

        # Sensitivity analysis for constraints

        file.write("\nConstraint sensitivity analysis:\n")

        for constr in lp_model.getConstrs():

            constr_name = constr.ConstrName

            constr_slack = constr.slack

            constr_dual_value = constr.getAttr("Pi")  

            file.write(f"Constraint: {constr_name}\n")

            file.write(f"  Slack: {constr_slack}\n")

            file.write(f"  Dual value (Shadow price): {constr_dual_value}\n")

Related to

• Attribute

0

• 

  Gwyneth Butera

  Gurobi Staff

  • April 06, 2024 14:09

  What is the error you get? Please share excerpts from the logfile so we can better understand the issue. -G

  0

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