Journal Article

DREAM-Stellar: parallel and space efficient exact local alignment

Gottlieb, Simon Gene, Aasna, Evelin, Ehrhardt, Marcel, Reinert, Knut

2026

Overview

Background Searching large genomic data sets for local alignments poses a computational challenge. A particular obstacle is the handling of repetitive sequences that appear in various contexts and incur a high runtime cost. For practical homology search, it is important to develop a specific but sensitive filter. Good filters reduce the search space before alignment without missing significant matches. Results We introduce DREAM-Stellar, a parallelized, updated version of the pairwise local aligner Stellar. The new aligner, DREAM-Stellar, is composed of four steps: preprocessing the queries and references, building a data structure for distributing the queries, computing in parallel the results and finally combining them. For distributing the queries we use the IBF data structure and a new prefilter for local alignments. We present our comparison of five local aligners on simulated and real genomic data and conclude that heuristic tools like BLAST miss a large percentage of significant local alignments or \"drown\" them in millions of less significant matches. This new version of Stellar is up to 900 times faster on 32 parallel threads than its single-threaded predecessor and can find all alignments between a pair of genomes in minutes. With that, the runtime of DREAM-Stellar is on par with tools like BLAST etc. Conclusions DREAM-Stellar is very practical and fast on very long sequences which makes it a suitable new tool for finding local alignments between genomic sequences under the edit distance model. The software is freely available for Linux and Mac OS X at https://github.com/seqan/dream-stellar

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Algorithms / Alignment / Amino acid sequence / Bioinformatics / Biomedical and Life Sciences / Computational biology / Computational Biology - methods / Computational Biology/Bioinformatics / Computer Appl. in Life Sciences / Data structures / Distributing / DNA sequencing / Genomes / Genomics / Genomics - methods / Homology / Life Sciences / Local alignments / Methods / Microarrays / Nucleotide sequencing / Parallel Algorithms / Parallel computing / Parallel processing / Prefilters / Queries / RNA sequencing / Run time (computers) / Seeds / Sequence Alignment - methods / Software