LP Iterative Rounding Using Concert C++

Question

I'm working on LP iterative rounding using concert c++. My ILP and LP codings work properly. However when i try to round LP iterativly i get infeasible soulution. In every iteration i try to find maximum value of decision variable x which is float number between 0-1 and make it 1(actually i'm adding it as a new constraint). However sometimes i get infeasible solution which actually shouldn't be a case. Error is as below: Infeasible indicator constraint presolve time:3.53 sec. Error:cplex Error 1217: No solution exists.

I'm working on a graph and trying to find a shorthest path. My ILP find path properly. However i need LP solution for big graphs. For that purpose wrote a LP formula. As result I got float numbers. Here I iteratively rounding one edge to 1. Finally i try to get a path.

And my code is as below:

    do
  { 
        max=0;
       for(int i=0; i<edgesize*2;i++)
       {
        if(cplex.getValue(x[i])>0 && cplex.getValue(x[i])<1 && cplex.getValue(x[i])>max )
        {
            max = cplex.getValue(x[i]);
        }
       }

       if(max !=0)
       {
         for(int i=0; i<edgesize*2;i++)
         {
                if(cplex.getValue(x[i])==max)
                {

                    model.add(x[i]==1);

                    break;
                }

         }


        }
    cplex.extract(model);
    cplex.solve();
    cplex.out() << "Optimal value: " << cplex.getObjValue() << endl;
    it++;


  } while(max !=0);

What would be a problem here? How can i solve it? Thanks in Advance.

Answer 1

I am a beginner in programming. I am trying to solve MILP by C and cplex concert technology

When i run I received the following message

Pr=1.00 X  ILO Array::operator[][](Iloint i): out of bound operation: index superior to size of array
Assertaion failed: (i<_impl->get size()) ||(ILOSTD(cerr)<<”X IloArray::operator[] (Iloint i): out of bounds operation: index superior to size of array”<< ILOSTD(endl), ilo_stop_ assert()).file c:\program file\ibm\ilog\cplex-studio 125\concert\include\ilconcert\iloenv.h, line 2204