1. An apparatus configured to efficiently group a set of strings into clusters of related strings, the apparatus comprising: data storage configured to store computer-readable code and data; a processor configured to access the data storage and to execute said computer-readable code; computer-readable code configured to receive the set of strings; computer-readable code configured to determine a binary output of an evaluation function between a pair of strings by steps including (i) generating a hash table based on a first string, (ii) matching sub-strings of a second string against the first string using the hash table, (iii) recording matches in a list, and (iv) applying a threshold based at least in part on a length of common substrings between the first and second strings; and computer-readable code configured to group the strings in the set into clusters by a procedure which, for each string that does not already belong to a cluster, determines the binary output of the evaluation function between the string and each other string in the set that do not yet belong to any cluster.