On optimally partitioning a text to improve its compression

In this paper we investigate the problem of partitioning an input string T in such a way that compressing individually its parts via a base-compressor gets a compressed output that is shorter than applying over the entire T at once. This problem was introduced in [2,3] in the context of table compression, and further elaborated and extended to strings and trees by [10,11,20], but it is still open how to efficiently compute the optimal partition [4]. In this paper we provide the first algorithm which is guaranteed to compute in O(n polylog(n)) time a partition of T whose compressed output is guaranteed to be no more than (1 + ε)-worse the optimal one, where ε is any positive constant.