We also apply two of the operators in a special fashion. The “fine tuning” parameters UmaxHint and SelectiveHint are intended to be effective at taking a solution that is nearly valid and improving the remaining problems in a focused manner. Given enough generations these improvements will be attempted on the best chromosomes, and tournament selection gives the best chromosomes a better chance at being selected. However, given the expense of fitness calculation a more opportunistic approach is to make sure that the best known chromosomes have had these “fine tuning” operators applied. With the SelectiveHint operator applied in this fashion we used a probability of 1.0, so that both it and UmaxHint will produce the same offspring chromosome if applied to the same parent chromosome twice. Checking for duplicates before evaluation then ensures that we will make sure we've tried these operators on the best chromosomes but will only force this to happen once for each.