1. A method, comprising: selecting, using a computer including a processor, a first group of indexes to form a current generation of indexes; selecting indexes from the first group biased to indexes with higher fitness values from the current generation of indexes; forming sub-groups of indexes using the selected indexes; determining fitness values of each of the sub-groups based on the fitness value of each of the indexes; selecting a subset of the sub-groups; and placing the indexes in the selected sub-groups into a new generation of indexes.