Do not print "Set parameter Username" in console

Answered

Allyson Silva

• December 02, 2021 15:46

I am using the C++ API and recently updated my Gurobi version from 9.1 to 9.5. It seems there is a new feature that prints "Set parameter XXX" when a parameter is manually set in the new version. I have been using Gurobi to solve an optimization problem that requires calling new environments multiple times sequentially. As so, I don't want to print anything from Gurobi in my console to keep it clean. I followed the second suggestion in this nice post to suppress all console output. However, even when setting OutputFlag 0 in an external file, the console still prints "Set parameter Username" after every new environment creation. How can I suppress that?

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  Jaromił Najman

  Gurobi Staff

  • December 02, 2021 16:02

  In order to suppress the "Set parameter XXX" output, you have to set the parameter OutputFlag as the first parameter in your environment, i.e., 

  // Create an environment
  GRBEnv env = GRBEnv(true);
  env.set(GRB_IntParam_OutputFlag,0);
  // Rest of your code

  Best regards,
  Jaromił

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  Allyson Silva

  • December 03, 2021 02:55

  

  

  

  Thanks for the quick answer, Jaromił!
  
  In fact, my problem is that I am creating the GRBEnv and GRBModel as attributes of a class as:

  class MyProblem {
    public:
      GRBEnv env;
      GRBModel model = GRBModel(env);
      // ...
      void setModel();
  }

  and adding model.set(GRB_IntParam_OutputFlag, 0) as the first command in void setModel(). After your suggestion, I could contour the problem by adding a constructor to initialize env before model as:

  class MyProblem {
    public:
      GRBEnv env;
      GRBModel model;
  
      // Constructor to set OutputFlag before creating my model
      MyProblem() : env(true), model(createModel(env)) {};
  
      GRBModel createModel(GRBEnv& env);
      void setModel();
  }
  
  // Set OutputFlag to 0 in env
  GRBModel MyProblem::createModel(GRBEnv& env) {
    env.set(GRB_IntParam_OutputFlag, 0);
    env.start();
    return GRBModel(env);
  }

  I will leave this here in case it may be helpful to someone else.

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• 

  Florian Götz

  • March 03, 2023 11:13

  

  

  Hello,

  could someone please post a solution for python users?

  Thanks a lot.

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• 

  Jaromił Najman

  Gurobi Staff

  • March 03, 2023 12:18

  could someone please post a solution for python users?

  The Python solution can be found in the Knowledge Base article How do I suppress all console output from Gurobi?

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