1. A similarity search initialization system comprising: a leaf selector to select a leaf of a suffix tree generated from a target string representing a target sequence, the selected leaf being associated with a prefix in the suffix tree having a longest match to a suffix of a query string representing a query; and a distance module to determine a distance between the query and a subsequence of the target sequence that is represented by a candidate substring of the target string, the candidate substring comprising the prefix associated with the selected leaf, wherein the determined distance is to provide an initial upper bound in a similarity search of the target sequence using the query.