This part is unclear; what exactly did you change? Are you saying that the LP relaxation has value 271.666, but, when you enforce integrality, Gurobi can actually find and prove optimality of a solution with value 218?
Were you really just solving LPs up to this point in the article? How can these intermediate LPs be so slow to solve (6+ years) and yet Gurobi is able to solve the integer-restricted problem?
Were you really just solving LPs up to this point in the article? How can these intermediate LPs be so slow to solve (6+ years) and yet Gurobi is able to solve the integer-restricted problem?