Originally posted by: xuxiaoming

Hi all,

I have a problem when I use SetVectors method. Please look at the following code. " SetVectors(_a[i], _A[i], null, null); and SetVectors(_myu[i][k], _Myu[i][k], null, null);" can pass the debug. However " SetVectors(_xiaa[i][j], _xiAA[i][j], null, null); etc" can not pass. The debug information shows that something is null. Then give a nullreferenceexception. I check every Inumvar carefully. And all of them are non-null. I spent two days to dweal with this problem.  However, I can't solve it.

So, can you help me?

Thanks a lot!

Xiaoming

 if (!_done)
                {
                    for (int i = 0; i < _A.GetLength(0); i++)
                    {
                        SetVectors(_a[i], _A[i], null, null);
                        SetVectors(_d[i], _D[i], null, null);
                    }

                    //for (int i = 0; i < _xiAA.GetLength(0); i++)
                    //    for (int j = 0; j < _xiAA[i].GetLength(0); j++)
                    //    {
                    //        SetVectors(_xiaa[i][j], _xiAA[i][j], null, null);
                    //        SetVectors(_xidd[i][j], _xiDD[i][j], null, null);
                    //        SetVectors(_xiad[i][j], _xiAD[i][j], null, null);
                    //        SetVectors(_xida[i][j], _xiDA[i][j], null, null);
                    //    }

                    for (int i = 0; i < _Myu.GetLength(0); i++)
                        for (int k = 0; k < _Myu[i].GetLength(0); k++)
                            SetVectors(_myu[i][k], _Myu[i][k], null, null);

                    //for (int i = 0; i < _Omega.GetLength(0); i++)
                    //    for (int j = 0; j < _Omega[i].GetLength(0); j++)
                    //        for (int k = 0; k < _Omega[i][j].GetLength(0); k++)
                    //            SetVectors(_omega[i][j][k], _Omega[i][j][k], null, null);

                    _done = true;
                }

Could it be that one of the arrays you are passing in is null itself? If the INumVar array is good, then maybe the double[] array is null?

Also, I am wondering about the context of your code? Is this in a solve callback? I am asking because Cplex class does not have an overload of SetVectors() that only takes four arguments.

Note that SetVectors() has been deprecated since version 12.5.

Originally posted by: xuxiaoming

Thanks for your help! The double[] array is also non-null! Yes the cods is in a solve callback. I have used SetStart method. But it also did not work. So, is there anything I can do to improve my code? Thanks a lot!

I got the slotution for the post problem.

Reference https://www.ibm.com/developerworks/community/forums/html/topic?id=77777777-0000-0000-0000-000014530212

see below

The exception is thrown when you attempt to get the value of a variable or a constraint that is not part of the model.

Each variable for which you invoke getValue() must appear in at least one constraint or in the objective function.
Double check your model and make sure that the variables for which you want to obtain the value are indeed part of the model.
If, for some reason, the variable does not occur in the objective function nor in any constraint but you still want to be able to get its value (although this value will be useless) then do cplex.extract(variable) before you do cplex.solve(). After this cplex.getValue(variable) should work without throwing an exception.

Hm, the post you cited was about an UnknownObjectException, not a null pointer exception. So which of the two exceptions did you observe?

Originally posted by: xuxiaoming

Hi, DanielJunglas

In fact, when I want to get the value of an array, sometimes an UnknownObjectException is throwed out.  So I searched for the solution for this problem, then, the solution method in the reference  is found, and it did work. Therefore, I think the null pointer exception problem may have the same bug. I corrected my code according the same solution.  Fortunately, the null pointer exception problem is also solved.