Inducing Suffix and LCP Arrays in External Memory

Abstract

We consider full text index construction in external memory (EM). Our first contribution is an inducing algorithm for suffix arrays in external memory, which runs in sorting complexity. Practical tests show that this algorithm outperforms the previous best EM suffix sorter [Dementiev et al., JEA 2008] by a factor of about two in time and I/O volume. Our second contribution is to augment the first algorithm to also construct the array of longest common prefixes (LCPs). This yields a new internal memory LCP array construction algorithm and the first EM construction algorithm for LCP arrays. The overhead in time and I/O volume for this extended algorithm over plain suffix array construction is roughly two. Our algorithms scale far beyond problem sizes previously considered in the literature (text size of 80GiB using only 4GiB of RAM in our experiments).