On the compression of search trees

Abstract

Let X = x1, x2, . . . , xn be a sequence of non-decreasing integer values. Stor- ing a compressed representation of X that supports access and search is a problem that occurs in many domains. The most common solution to this problem uses a linear list and encodes the differences between consecu- tive values with encodings that favor small numbers. This solution includes additional information (i.e. samples) to support efficient searching on the en- coded values. We introduce a completely different alternative that achieves compression by encoding the differences in a search tree. Our proposal has many applications, such as the representation of posting lists, geographic data, sparse bitmaps, and compressed suffix arrays, to name just a few. The structure is practical and we provide an experimental evaluation to show that it is competitive with the existing techniques.