title: Gurobi doesn't stop at optimal objective value of 0
body: <p>I'm trying to solve a rather complex optimization problem with Gurobi 7.0.1. The objective function is a sum of three continuous variables, each with a lower bound of 0 (default).</p>
  
  <p>The optimization with Gurobi has been running on a VM for over a week now. When looking into the log, I can see that Gurobi already found many solutions with objective 0 but still has no Gap. It seems like, Gurobi has trouble dealing with the objective value 0 and can't bound it.</p>
  
  <p>On the other hand, some other runs with different parameters quickly terminated despite having an objective value of 0 (and Gap 100%).</p>
  
  <p>Is it possible that Gurobi is really struggling with the objective value 0 and doesn't recognize, it's the optimal value? If so, why does it only happen sometimes and what can I do to speed things up?</p>