Practical Parallel Lempel-Ziv Factorization

Abstract

In the age of big data, the need for efficient data compression algorithms has grown. A widely used data compression method is the Lempel-Ziv-77 (LZ77) method, being a subroutine in popular compression packages such as gzip and PKZIP. There has been a lot of recent effort on developing practical sequential algorithms for Lempel-Ziv factorization (equivalent to LZ77 compression), but research in practical parallel implementations has been less satisfactory. In this work, we present a simple work-efficient parallel algorithm for Lempel-Ziv factorization. We show theoretically that our algorithm requires linear work and runs in O(log2 n) time (randomized) for constant alphabets and O(nϵ) time (ϵ <; 1) for integer alphabets. We present experimental results showing that our algorithm is efficient and achieves good speedup with respect to the best sequential implementations of Lempel-Ziv factorization.