Welcome to the odgi documentation!¶
In standard genomic approaches sequences are related to a single linear reference genome introducing reference bias. Pangenome graphs encoded in the variation graph data model describe the all versus all alignment of many sequences. Representing large pangenome graphs with minimal memory overhead requires a careful encoding of the graph entities. It is possible to build succinct, static data structures to store queryable graphs, as in xg, but dynamic data structures are more tricky to implement.
The optimized dynamic genome/graph implementation odgi follows the dynamic
GBWT in developing
a byte-packed version of the graph, edges, and paths through it. The node’s id is stored as a uint64_t and its
sequence is stored as a plain std::string. Bit-compressed dynamic byte arrays, with a local alphabet encoder,
represent the local neighbourhood
of the node:
The node’s edges, and
the paths crossing the node.
To ensure minimal memory occupation, only the deltas of the neighbouring steps of a path are hold.
odgi provides a set of tools ranging from graph building, manipulation, layouting, over graph statistics to graph
visualization and gene annotation lift overs.