Abstract
Pattern matching is a key step in a variety of biological sequence analysis pipelines. The FM-index is a compressed data structure for pattern matching, with search run time that is independent of the length of the database text. We present AvxWindowedFMindex (AWFM-index), an open-source, thread-parallel FM-index library written in C that is highly optimized for indexing nucleotide and amino acid sequences. AWFM-index is easy to incorporate into bioinformatics software and is able to perform exact match count and locate queries approximately 4x faster than Seqan3’s FM-index implementation for nucleotide search, and approximately 8x faster for amino acid search in a single-threaded context. This performance is due to (i) a new approach to storing FM-index data in a strided bit-vector format that enables extremely efficient computation of the FM-index occurrence function via AVX2 bitwise instructions, and (ii) inclusion of a cache-efficient lookup table for partial k-mer searches. AWFM-index also trivially parallelizes to multiple threads, and scales well in multithreaded contexts. The open-source library is available for download at https://github.com/TravisWheelerLab/AvxWindowFmIndex.
Author summary AvxWindowedFMIndex is a fast, open-source library implementation of the FM-index algorithm. This library takes advantage of powerful ‘single-instruction, multiple data’ (SIMD) CPU instructions to quickly perform the most difficult part of the algorithm, counting the number of occurrences of a given letter in a block of text. Algorithms like FM-index are widely used many places in bioinformatics like biosequence database searching, taxonomic classification, and sequencing error correction. Using the AvxWindowedFMIndex library will ease the burden of including the FM index into bioinformatic software, thus enabling faster pattern matching and overall faster software in practice.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Minor changes to text, change corresponding author.
http://wheelerlab.org/publications/2021-AWFM-Anderson/Anderson_suppl.tar.gz
