gaftools: a toolkit for analyzing and manipulating pangenome alignments

Linear reference genomes are ubiquitously used in genomics research, despite known biases associated with their use. In recent years, there has a been a shift towards using graph-based reference genomes to address some of these biases, which has required new algorithms and file formats to be developed. This has created the need to develop new tools capable of utilizing these formats and performing operations similar to those carried out by traditional methods.In this paper we present “gaftools”, a multi-purpose tool that introduces several utilities for processing graph alignments in GAF format. Gaftools enables users to index and sort alignments, with graph ordering serving as a necessary step for the sorting process. Additionally it allows users to view subsets of alignments and perform realignment using the wavefront alignment algorithm, among other useful features. Many of these functionalities are inspired by SAMtools, which provide similar operations for linear genomes, while gaftools adapts and extends them for pangenomes.