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Model status returns GRB_LOADED

Answered
Yuyi Zhong
  • Gurobi-versary
  • Conversationalist
  • First Question

Hi, 

I am running Gurobi 9.0 in the C language.

One of the model solving returns me status "GRB_LOADED", meaning that the Model is loaded, but no solution information is available.

Do you have any idea why would this happen? I currently don't know how to debug this error.

Thank you!

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11 comments

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  • Official comment
    Simranjit Kaur
    • Gurobi Staff
    This post is more than three 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.
  • Jaromił Najman
    • Gurobi Staff
    Edited

    Hi,

    The status \(\texttt{GRB_LOADED}\) means that there is a model at hand, because, e.g., a model has been read in from a file or constructed manually, but no call to the GRBoptimize method has been performed yet.

    Best regards,
    Jaromił

    0
  • Yuyi Zhong
    • Gurobi-versary
    • Conversationalist
    • First Question

    Hi,

    Thanks, but I am actually solving a multi-scenario model https://www.gurobi.com/documentation/9.0/refman/definition_of_a_multi_scen.html.,

    where a single call to the standard Gurobi optimize method is all that is needed to solve all scenarios. 

    I called GRBoptimize once and get "GRB_OPTIMAL" for other scenarios, but why one scenario returns me "GRB_LOADED"?

     

    0
  • Jaromił Najman
    • Gurobi Staff

    If a model is solved via \(\texttt{optimize}\), it does not matter what type of model it is, i.e., it does not matter whether it is a multi-scenario model or not. If a model has not been solved yet, then the model status is \(\texttt{GRB_LOADED}\). Do you mean that you are trying to retrieve the status of each scenario of a multi-scenario model? Could you please share a reproducible example and a LOG file showing this issue?

    Best regards,
    Jaromił

    0
  • Yuyi Zhong
    • Gurobi-versary
    • Conversationalist
    • First Question

    I am trying to retrieve the ObjVal for each scenario, but I had "Gurobi error: Unable to retrieve attribute 'ScenNObjVal'" for one of the scenarios. After checking, I find that the model status for the failed scenario is GRB_LOADED.

    Please allow me some time to get the example code and LOG file, thanks.

     

     

     

     

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  • Yuyi Zhong
    • Gurobi-versary
    • Conversationalist
    • First Question

    Hi,

    The overall code is very long, I provided the skeleton, where I create multiple scenarios with the different objective functions (the objective function in base model is 0), then call GRBupdatemodel, finally retrieve the ScenNObjVal for each scenario.

    int var_ind_record[MAX_ITER+2]; //assume that the list has been assigned
    error = GRBsetintattr(model, "NumScenarios", MAX_ITER*3);
    handle_gurobi_error(error, env);
    error = GRBupdatemodel(model);
    handle_gurobi_error(error, env);
    for(j=0; j < MAX_ITER; j++){
    int index1 = var_ind_record[j];
    int index2 = var_ind_record[j+1];
    int index3 = var_ind_record[j+2];
    // Compute z1 + z3
    error = GRBsetintparam(GRBgetenv(model), "ScenarioNumber", j*3);
    handle_gurobi_error(error, GRBgetenv(model));
    error = GRBsetdblattrelement(model, "ScenNObj", index3, 1.0);
    error = GRBsetdblattrelement(model, "ScenNObj", index1, 1.0);
    handle_gurobi_error(error, env);
    error = GRBupdatemodel(model);
    handle_gurobi_error(error, env);
    // Compute z2 + z3
    error = GRBsetintparam(GRBgetenv(model), "ScenarioNumber", j*3+1);
    handle_gurobi_error(error, GRBgetenv(model));
    error = GRBsetdblattrelement(model, "ScenNObj", index3, 1.0);
    error = GRBsetdblattrelement(model, "ScenNObj", index2, 1.0);
    handle_gurobi_error(error, env);
    error = GRBupdatemodel(model);
    handle_gurobi_error(error, env);
    // Compute z1 + z2 + z3
    error = GRBsetintparam(GRBgetenv(model), "ScenarioNumber", j*3+2);
    handle_gurobi_error(error, GRBgetenv(model));
    error = GRBsetdblattrelement(model, "ScenNObj", index3, 1.0);
    error = GRBsetdblattrelement(model, "ScenNObj", index2, 1.0);
    error = GRBsetdblattrelement(model, "ScenNObj", index1, 1.0);
    handle_gurobi_error(error, env);
    error = GRBupdatemodel(model);
    handle_gurobi_error(error, env);
    }
    // Do the multi-scenario solving
    error = GRBsetintattr(model, "ModelSense", -1); //maximization
    handle_gurobi_error(error, env);
    error = GRBupdatemodel(model);
    handle_gurobi_error(error, env);
    error = GRBoptimize(model);
    handle_gurobi_error(error, env);
    error = GRBgetintattr(model, GRB_INT_ATTR_STATUS, &optimstatus);
    handle_gurobi_error(error, env);
    double solved_ub;
    for(j=0; j < MAX_ITER; j++){
    int index1 = var_ind_record[j];
    int index2 = var_ind_record[j+1];
    int index3 = var_ind_record[j+2];
    error = GRBsetintparam(GRBgetenv(model), "ScenarioNumber", 3*j);
    handle_gurobi_error(error, GRBgetenv(model));
    error = GRBgetintattr(model, GRB_INT_ATTR_STATUS, &optimstatus);
    handle_gurobi_error(error, env);
    error = GRBgetdblattr(model, "ScenNObjVal", &solved_ub);
    handle_gurobi_error(error, env);

    error = GRBsetintparam(GRBgetenv(model), "ScenarioNumber", 3*j+1);
    handle_gurobi_error(error, GRBgetenv(model));
    error = GRBgetintattr(model, GRB_INT_ATTR_STATUS, &optimstatus);
    handle_gurobi_error(error, env);
    error = GRBgetdblattr(model, "ScenNObjVal", &solved_ub);
    handle_gurobi_error(error, env);

    error = GRBsetintparam(GRBgetenv(model), "ScenarioNumber", 3*j+2);
    handle_gurobi_error(error, GRBgetenv(model));
    error = GRBgetintattr(model, GRB_INT_ATTR_STATUS, &optimstatus);
    handle_gurobi_error(error, env);
    error = GRBgetdblattr(model, "ScenNObjVal", &solved_ub);
    handle_gurobi_error(error, env);

    }
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  • Yuyi Zhong
    • Gurobi-versary
    • Conversationalist
    • First Question

    The printed-out log information is given as followed, where you can see that "Scenario 12 has been solved. 0/49 scenarios left." So all the scenarios should have been solved, but I don't know why scenario 4 is "GRB_LOADED" and cannot retrieve attribute 'ScenNObjVal'. Thank you for your help!

    Academic license - for non-commercial use only
    Gurobi Optimizer version 9.0.0 build v9.0.0rc2 (linux64)

    Warning: excessive time spent in model updates.
    Consider calling update less frequently.

    Optimize a model with 2777 rows, 4004 columns and 442744 nonzeros
    Model fingerprint: 0x01e59090
    Variable types: 4004 continuous, 0 integer (0 binary)
    Coefficient statistics:
    Matrix range [1e-07, 2e+00]
    Objective range [1e+00, 1e+00]
    Bounds range [2e-04, 2e+01]
    RHS range [2e-04, 2e+00]

    Solving a multi-scenario model with 49 scenarios...

    Presolve removed 381 rows and 1290 columns
    Presolve time: 0.56s
    Presolved: 2511 rows, 2877 columns, 150518 nonzeros
    Variable types: 2828 continuous, 49 integer (49 binary)

    Root relaxation: objective 7.985614e-01, 1426 iterations, 0.71 seconds

    Nodes | Current Node | Objective Bounds | Work
    Expl Unexpl | Obj Depth IntInf | Incumbent BestBd Gap | It/Node Time

    0 0 0.79857 0 2 - 0.79857 - - 1s
    H 0 0 0.4968513 0.79857 60.8% - 1s
    H 0 0 0.5932906 0.79857 34.6% - 1s
    0 0 0.70217 0 2 0.59330 0.70217 18.4% - 2s
    0 0 0.69374 0 3 0.59330 0.69374 17.0% - 2s
    Scenario 47 has been solved. 48/49 scenarios left.
    Scenario 48 has been solved. 47/49 scenarios left.
    0 0 0.69107 0 4 0.59330 0.69107 16.5% - 3s
    0 0 0.69093 0 4 0.59330 0.69093 16.5% - 3s
    0 0 0.69021 0 4 0.59330 0.69021 16.4% - 3s
    Scenario 43 has been solved. 46/49 scenarios left.
    Scenario 45 has been solved. 45/49 scenarios left.
    0 0 0.69001 0 4 0.59330 0.69001 16.4% - 4s
    Scenario 44 has been solved. 44/49 scenarios left.
    0 0 0.68981 0 4 0.59330 0.68981 16.3% - 5s
    0 2 0.68981 0 4 0.59330 0.68981 16.3% - 11s
    Scenario 39 has been solved. 43/49 scenarios left.

    Optimal solution found at node 19 - now completing multiple scenarios...

    Nodes | Current Node | Scenario Obj. Bounds | Work
    | | Worst |
    Expl Unexpl | Obj Depth IntInf | Incumbent BestBd Gap | It/Node Time

    19 2 0.54867 10 2 - 0.54867 - 175 13s
    Scenario 38 has been solved. 42/49 scenarios left.
    Scenario 42 has been solved. 41/49 scenarios left.
    Scenario 18 has been solved. 40/49 scenarios left.
    Scenario 21 has been solved. 39/49 scenarios left.
    Scenario 27 has been solved. 38/49 scenarios left.
    Scenario 30 has been solved. 37/49 scenarios left.
    Scenario 35 has been solved. 36/49 scenarios left.
    Scenario 36 has been solved. 35/49 scenarios left.
    Scenario 14 has been solved. 34/49 scenarios left.
    Scenario 17 has been solved. 33/49 scenarios left.
    Scenario 19 has been solved. 32/49 scenarios left.
    Scenario 26 has been solved. 31/49 scenarios left.
    Scenario 33 has been solved. 30/49 scenarios left.
    Scenario 37 has been solved. 29/49 scenarios left.
    55 2 0.37685 28 2 - 0.37685 - 96.9 15s
    Scenario 31 has been solved. 28/49 scenarios left.
    Scenario 34 has been solved. 27/49 scenarios left.
    Scenario 24 has been solved. 26/49 scenarios left.
    Scenario 1 has been solved. 25/49 scenarios left.
    Scenario 15 has been solved. 24/49 scenarios left.
    Scenario 23 has been solved. 23/49 scenarios left.
    Scenario 25 has been solved. 22/49 scenarios left.
    Scenario 40 has been solved. 21/49 scenarios left.
    Scenario 0 has been solved. 20/49 scenarios left.
    Scenario 22 has been solved. 19/49 scenarios left.
    Scenario 28 has been solved. 18/49 scenarios left.
    Scenario 29 has been solved. 17/49 scenarios left.
    Scenario 3 has been solved. 16/49 scenarios left.
    Scenario 13 has been solved. 15/49 scenarios left.
    Scenario 16 has been solved. 14/49 scenarios left.
    Scenario 32 has been solved. 13/49 scenarios left.
    Scenario 41 has been solved. 12/49 scenarios left.
    Scenario 20 has been solved. 11/49 scenarios left.
    Scenario 10 has been solved. 10/49 scenarios left.
    Scenario 46 has been solved. 9/49 scenarios left.
    Scenario 2 has been solved. 8/49 scenarios left.
    Scenario 4 has been solved. 7/49 scenarios left.
    Scenario 5 has been solved. 6/49 scenarios left.
    Scenario 6 has been solved. 5/49 scenarios left.
    Scenario 7 has been solved. 4/49 scenarios left.
    Scenario 8 has been solved. 3/49 scenarios left.
    Scenario 9 has been solved. 2/49 scenarios left.
    Scenario 11 has been solved. 1/49 scenarios left.
    Scenario 12 has been solved. 0/49 scenarios left.

    Cutting planes:
    Gomory: 1
    MIR: 40
    RLT: 7

    Explored 87 nodes (9121 simplex iterations) in 16.27 seconds
    Thread count was 24 (of 24 available processors)

    Solution count 10: 0.593291 0.496852 0.472511 ... 0.407121
    No other solutions better than 0.593291

    Optimal solution found (tolerance 1.01e-04)
    Best objective 5.932905623862e-01, best bound 5.932905623862e-01, gap 0.0000%
    The solution status is 2
    The ScenarioNumber is 0, the solution status is 2
    The ScenarioNumber is 1, the solution status is 2
    The ScenarioNumber is 2, the solution status is 2
    The ScenarioNumber is 3, the solution status is 2
    The ScenarioNumber is 4, the solution status is 1 (GRB_LOADED)
    Gurobi error: Unable to retrieve attribute 'ScenNObjVal'
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  • Jaromił Najman
    • Gurobi Staff
    Edited

    Hi,

    Could you try updating to the latest version 9.5.0 ?

    If this does not help, could you generate an LP or MPS file of your model using the GRBwrite method and share it such that I can try to reproduce this behavior on my side?

    Best regards,
    Jaromił

    0
  • Yuyi Zhong
    • Gurobi-versary
    • Conversationalist
    • First Question

    Hi,

    Thanks for your suggestion, but updating to 9.5.0 doesn't really help.

    I didn't see a button to attach files, how can I share lp and mps files to you? 

    Thanks and Regards,

    Yuyi

    0
  • Yuyi Zhong
    • Gurobi-versary
    • Conversationalist
    • First Question

    Hi,

    I think I know the reason, I added new constraints to the model and updated the model before scenario 4.

    Since the base model is modified, scenario 4 returns "GRB_LOADED". I delayed my calling to

    GRBupdatemodel() function, now it works fine.
     
    Thank you so much for your patience and kind help!!
     
    Best regards,
    Yuyi
    0
  • Jaromił Najman
    • Gurobi Staff

    Great to hear that your were able to solve the issue!

    0

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