Error when assigning a GRBVar into a 3d dynamically array in c++

Answered

Giorgos Tsoumos

March 03, 2023 05:04

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Hello,

I have a problem with the assignment  of a GRBVar into a 3d dynamically allocated array in C++ and i dont know why the error occures. The code is down below so 

 

// In test.cpp

GRBVar*** init_x(GRBVar*** x)
    {

        GRBVar tmp;

        x = new GRBVar * *[customers];

        for (int i = 0; i < customers; i++)
        {
            x[i] = new GRBVar * [customers];
            for (int k = 0; k < vehicles; k++)
              {
                    x[i][k] = new GRBVar[vehicles];
               }
        }

        return x;

    }

 

// in main.cpp

int main(int argc,char* argv[])

{

GRBVar*** _x{};

 GRBVar*** x= init_x(_x);

 

 for (int i = 0; i < customers; i++)
        {
            for (int j = 0; j < customers; j++)
            {
                for (int k = 0; k < vehicles; k++)
                {
                    x[i][j][k] =  model.addVar(0.0, 1.0, 0.0, GRB_BINARY, "from x_ " + std::to_string(i) + " goes to " + std::to_string(j) + " with vehicle " + std::to_string(k)); // Here is the error while the compilation is ok the debugging shows me a problem with the operator =
                }
            }
        }

 

Thanks in advance.

Related to

• Error
• C++

0

• 

  Marika Karbstein

  • Gurobi Staff

  March 03, 2023 12:18

  Hi Giorgos,

  Could you please share the error you see?
  Your code is not directly reproducible. But if I initialize customers, vehicles, and the Gurobi model 

  int customers = 4;
  int vehicles = 5;
  GRBEnv* env = new GRBEnv();
  GRBModel model = GRBModel(*env);

  I can compile without errors.

  Best regards,
  Marika

  0
• 

  Giorgos Tsoumos

  March 03, 2023 12:43

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  Yes the error is directing me in this line of gurobi_c++.h which is

  GRBVar& operator=(const GRBVar& xvar) { varRep = xvar.varRep; return *this; }

  and the error is 

  "Exception thrown: read access violation.
  this was 0xFFFFFFFFFFFFFFFF."

   

   

  0
• 

  Marika Karbstein

  • Gurobi Staff

  March 03, 2023 13:02

  Could you post the full example?
  What do you mean by "the debugging shows" the error?

  0
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  Giorgos Tsoumos

  March 03, 2023 13:27

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  Yes sure, 

  I am running this code in VS 2019 and when i start debugging

  then an exception is thrown that points me to this line of "gurobi_c++.h" file 

  "GRBVar& operator=(const GRBVar& xvar) { varRep = xvar.varRep; return *this; }"

  I made some moving from main.cpp to this function in test.cpp 

  namespace PDPTW_Init 
  {

  int vehicles = 10;

  int customers = 101;

      GRBVar***  init_x(GRBModel& model)
      {
          

          GRBVar ***x = new GRBVar * *[customers];

          for (int i = 0; i < customers; i++)
          {
              x[i] = new GRBVar * [customers];
              for (int k = 0; k < vehicles; k++)
                {
                      x[i][k] = new GRBVar[vehicles];
                 }
          }

          // Initialize x if vehicle goes from node i to node j
          for (int i = 0; i < customers; i++)
          {
              for (int j = 0; j < customers; j++)
              {
                  for (int k = 0; k < vehicles; k++)
                  {
                      std::string msg = "from x_ " + std::to_string(i) + " goes to " + std::to_string(j) + " with vehicle " + std::to_string(k);
                      x[i][j][k] = model.addVar(0.0, 1.0, 0.0, GRB_BINARY, "x");
                  }
              }
          }

   

          return x;

      }

  };

  // main.cpp

  #include "PDPTW_Init.h"
  #include "gurobi_c++.h"
  #include<string>

  
  int main(int argc, char* argv[])
  {

  
      GRBVar*** x = nullptr;

  try
      {
          GRBEnv env = GRBEnv();
          GRBModel model = GRBModel(env);

          // Set variables
          
          x = PDPTW_Init::init_x(model);

  }

  catch (GRBException e)
      {
          std::cout << "Error code = "
              << e.getErrorCode()
              << std::endl;
          std::cout << e.getMessage() << std::endl;
      }
      catch (...)
      {
          std::cout << "Exception during optimization"
              << std::endl;
      }
    
      return 0;
  }

   

  0
• 

  Marika Karbstein

  • Gurobi Staff

  March 03, 2023 13:49 Edited

  I think your error is in init_x() when declaring the variables. The second for-loop should be

  for (int k = 0; k < customers; k++)

  instead of

  for (int k = 0; k < vehicles; k++)

   

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• 

  Giorgos Tsoumos

  March 03, 2023 13:52

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  God bless you! Thank you so much i am struggling with this for days... Solved <3 

  0

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