I have been working on an MIP in C#. I want to reduce the gap, so I'm trying warm start. I use this code just before solve().

        startvar = new IIntVar[numberOfAllNode * numberOfAllNode];
        startval = new double[numberOfAllNode * numberOfAllNode];

        for (int j = 1, idx = 0; j <= numberOfAllNode; j++)
            for (int i = 1; i <= numberOfAllNode; i++)
                startvar[idx] = x[j][i];
                startval[idx] = x_value[j,i];

        startvar = null;
        startval = null;
        Cplex.AddMIPStart(startvar[], startval[], Cplex.MIPStartEffort.SolveMIP);

I got some syntax errors in the last line. unfortunately, I don't know what variable should I write in startvar[].


1 Answer 1


This looks like a plain C# programming error.

  1. Don't set startvar and startval to null before calling AddMIPStart.
  2. Remove square brackets from startvar and startval in the cal to AddMIPStart.

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