Fast Iteration of Spaced k-mers

Fuente: arXiv
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Auteur principal: Czech, Lucas
Format: Preprint
Publié: 2026
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author Czech, Lucas
author_facet Czech, Lucas
contents Background: Short sequence substrings of a fixed length k, called k-mers, are a ubiquitous computational primitive in bioinformatics, used across sequence indexing, read mapping, genome assembly, metagenomic classification, and comparative genomics. Spaced k-mers generalize this concept by selecting only a subset of positions within a k-mer, improving robustness to mismatches and sequencing errors. While k-mers are computationally highly efficient, spaced k-mers require additional work to be extracted from a sequence, which has slowed down existing methods. Results: We present a collection of efficient algorithms for extracting spaced k-mers from nucleotide sequences, optimized for different hardware architectures. They are based on bit manipulation instructions at CPU level, making them both simpler to implement and up to an order of magnitude faster than existing methods. We further evaluate common pitfalls in k-mer processing, which can cause substantial inefficiencies. Conclusions: Our approaches allow the utilization of spaced k-mers in high-performance bioinformatics applications without major performance degradation compared to regular k-mers, achieving a throughput of up to 750MB of sequence data per second per core. Availability: The implementation in C++20 is published under the MIT license, and freely available at https://github.com/lczech/fisk
format Preprint
id arxiv_https___arxiv_org_abs_2603_25417
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Fast Iteration of Spaced k-mers
Czech, Lucas
Genomics
Data Structures and Algorithms
Background: Short sequence substrings of a fixed length k, called k-mers, are a ubiquitous computational primitive in bioinformatics, used across sequence indexing, read mapping, genome assembly, metagenomic classification, and comparative genomics. Spaced k-mers generalize this concept by selecting only a subset of positions within a k-mer, improving robustness to mismatches and sequencing errors. While k-mers are computationally highly efficient, spaced k-mers require additional work to be extracted from a sequence, which has slowed down existing methods. Results: We present a collection of efficient algorithms for extracting spaced k-mers from nucleotide sequences, optimized for different hardware architectures. They are based on bit manipulation instructions at CPU level, making them both simpler to implement and up to an order of magnitude faster than existing methods. We further evaluate common pitfalls in k-mer processing, which can cause substantial inefficiencies. Conclusions: Our approaches allow the utilization of spaced k-mers in high-performance bioinformatics applications without major performance degradation compared to regular k-mers, achieving a throughput of up to 750MB of sequence data per second per core. Availability: The implementation in C++20 is published under the MIT license, and freely available at https://github.com/lczech/fisk
title Fast Iteration of Spaced k-mers
topic Genomics
Data Structures and Algorithms
url https://arxiv.org/abs/2603.25417