1. A method of identifying repeat subsequences of symbols in a sequence of symbols comprising: receiving a sequence of symbols drawn from an alphabet, the sequence of symbols being generated from a collection of at least two documents; defining values of x and y, where x corresponds to a threshold number of different left contexts for a given repeat subsequence in the sequence and y corresponds to a threshold number of different right contexts for a given repeat subsequence in the sequence to be identified as context diverse; generating a lexicographically sorted array of suffixes in the sequence; computing a longest common prefix array, each value in the longest common prefix array representing a length, in symbols, of a longest common prefix that occurs in an adjacent pair of suffixes in the lexicographically sorted array; sequentially comparing pairs of first and second longest common prefix values that are sequential in the longest common prefix array and, based on the comparison, identifying at least one of: an occurrence of a same repeat subsequence, when the compared first and second longest common prefix values are the same; a new occurrence of a longer repeat subsequence when the second of the compared longest common prefix values is higher; and a last occurrence of a given repeat subsequence when the second of the compared longest common prefix values is lower; based on the sequential comparisons, identifying context diverse repeat subsequences in the sequence, each of the identified context diverse repeat subsequences having at least the defined threshold number of different left and right contexts; and outputting information based on the identified context diverse repeat subsequences, the output information including at least one of: a set of repeat subsequences which includes the identified context diverse repeat subsequences; a vector spaced representation of a document in the collection, the vector spaced representation including indices, each index representing a number of times a respective one of a set of repeat subsequences appears in the document, the set of repeat subsequences including the identified context diverse repeat subsequences; a label for a document in the collection, the label being based on the vector spaced representation of the document; for each of a set of topics, a set of most probable repeat subsequences from a set of repeat subsequences which includes the identified context diverse repeat subsequences; and a cluster of similar documents in the collection, or a set of documents similar to a selected document, based on a measure of similarity between respective vector spaced representations; wherein at least one of the generating, computing, comparing, and identifying is performed by a computer processor.