Crate graph[−][src]
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A library that can be used as a building block for high-performant graph algorithms.
Graph provides implementations for directed and undirected graphs. Graphs can be created programatically or read from custom input formats in a type-safe way. The library uses rayon to parallelize all steps during graph creation.
The implementation uses a Compressed-Sparse-Row (CSR) data structure which is tailored for fast and concurrent access to the graph topology.
Note: The development is mainly driven by Neo4j developers. However, the library is not an official product of Neo4j.
What is a graph?
A graph consists of nodes and edges where edges connect exactly two nodes. A graph can be either directed, i.e., an edge has a source and a target node or undirected where there is no such distinction.
In a directed graph, each node u
has outgoing and incoming neighbors. An
outgoing neighbor of node u
is any node v
for which an edge (u, v)
exists. An incoming neighbor of node u
is any node v
for which an edge
(v, u)
exists.
In an undirected graph there is no distinction between source and target
node. A neighbor of node u
is any node v
for which either an edge (u, v)
or (v, u)
exists.
How to use graph?
The library provides a builder that can be used to construct a graph from a given list of edges.
For example, to create a directed graph that uses usize
as node
identifier, one can use the builder like so:
use graph::prelude::*; let graph: DirectedCsrGraph<usize> = GraphBuilder::new() .edges(vec![(0, 1), (0, 2), (1, 2), (1, 3), (2, 3)]) .build(); assert_eq!(graph.node_count(), 4); assert_eq!(graph.edge_count(), 5); assert_eq!(graph.out_degree(1), 2); assert_eq!(graph.in_degree(1), 1); assert_eq!(graph.out_neighbors(1), &[2, 3]); assert_eq!(graph.in_neighbors(1), &[0]);
To build an undirected graph using u32
as node identifer, we only need to
change the expected types:
use graph::prelude::*; let graph: UndirectedCsrGraph<u32> = GraphBuilder::new() .edges(vec![(0, 1), (0, 2), (1, 2), (1, 3), (2, 3)]) .build(); assert_eq!(graph.node_count(), 4); assert_eq!(graph.edge_count(), 5); assert_eq!(graph.degree(1), 3); assert_eq!(graph.neighbors(1), &[0, 2, 3]);
It is also possible to create a graph from a specific input format. In the
following example we use the EdgeListInput
which is an input format where
each line of a file contains an edge of the graph.
use std::path::PathBuf; use graph::prelude::*; let path = [env!("CARGO_MANIFEST_DIR"), "resources", "example.el"] .iter() .collect::<PathBuf>(); let graph: DirectedCsrGraph<usize> = GraphBuilder::new() .csr_layout(CsrLayout::Sorted) .file_format(EdgeListInput::default()) .path(path) .build() .expect("loading failed"); assert_eq!(graph.node_count(), 4); assert_eq!(graph.edge_count(), 5); assert_eq!(graph.out_degree(1), 2); assert_eq!(graph.in_degree(1), 1); assert_eq!(graph.out_neighbors(1), &[2, 3]); assert_eq!(graph.in_neighbors(1), &[0]);
Examples?
Check the TriangleCount and PageRank implementations to see how the library is used to implement high-performant graph algorithms.
Modules
Structs
Enums
Traits
A graph where the order within an edge tuple is important.
A graph is a tuple (N, E)
, where N
is a set of nodes and E
a set of
edges. Each edge connects exactly two nodes.
A graph where the order within an edge tuple is unimportant.