Error at GRBVar.get

Answered

Samuele Valperta

May 14, 2024 23:58

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Hello, I need to find if the optimal solution found is a degenerate solution.

Being that there's no default method to do that my idea was, after optimising, to iterate through model.getVars() and check if there's some variable set to 0.

var.get(GRB.IntAttr.VBasis) == GRB.BASIC ...

(Placing the three dots because I still need to check the value of the var)

The problem is that I get this error and after struggling for hours I still can't find a solution

com.gurobi.gurobi.GRBException: Error at GRBVar.get

at com.gurobi.gurobi.GRBVar.get(GRBVar.java:84)

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 13, 2026 01:24

  This post is more than two years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
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  Simranjit Kaur

  • Gurobi Staff

  May 15, 2024 00:25

  Hi Samuele,

  The error you're encountering, com.gurobi.gurobi.GRBException: Error at GRBVar.get  is usually triggered due to accessing an attribute that is not available.

  The VBasis and CBasis attributes can only be queried when a simplex basis is available (a basis is available when a continuous model has been solved using primal simplex, dual simplex, or barrier with crossover). For example, these attributes are not available if you're solving via the barrier method without crossover. Please check if this is the case for your model.

  Best regards,
  Simran

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  Samuele Valperta

  May 15, 2024 00:33 Edited

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  Thank you very much! I was solving an integer problem

  Variable types: 0 continuous, 308 integer (154 binary)

  but I've just realised I was doing wrong and I need to switch to a continuous problem.

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