raphtory 0.17.0

raphtory, a temporal graph library
Documentation 
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use crate::{
    core::entities::VID,
    db::{
        api::{
            state::{GenericNodeState, TypedNodeState},
            view::StaticGraphViewOps,
        },
        graph::node::NodeView,
    },
    prelude::*,
};
use serde::{Deserialize, Serialize};
use std::collections::{HashMap, HashSet};

#[derive(Clone, PartialEq, Serialize, Deserialize, Debug, Default, Hash, Eq)]
pub struct SCCState {
    pub component_id: usize,
}

fn tarjan<'graph, G>(
    node: NodeView<&'graph G>,
    index: &'graph mut u64,
    stack: &'graph mut Vec<VID>,
    indices: &'graph mut HashMap<VID, u64>,
    lowlink: &'graph mut HashMap<VID, u64>,
    on_stack: &'graph mut HashSet<VID>,
    result: &'graph mut Vec<Vec<VID>>,
) where
    G: StaticGraphViewOps,
{
    *index += 1;
    indices.insert(node.node, *index);
    lowlink.insert(node.node, *index);
    stack.push(node.node);
    on_stack.insert(node.node);

    for neighbor in node.out_neighbours() {
        if !indices.contains_key(&neighbor.node) {
            tarjan(neighbor, index, stack, indices, lowlink, on_stack, result);
            lowlink.insert(node.node, lowlink[&node.node].min(lowlink[&neighbor.node]));
        } else if on_stack.contains(&neighbor.node) {
            lowlink.insert(node.node, lowlink[&node.node].min(indices[&neighbor.node]));
        }
    }

    if indices[&node.node] == lowlink[&node.node] {
        let mut component = Vec::new();
        let mut top = stack.pop().unwrap();
        on_stack.remove(&top);
        component.push(top);
        while top != node.node {
            top = stack.pop().unwrap();
            on_stack.remove(&top);
            component.push(top);
        }
        result.push(component);
    }
}

fn tarjan_scc<G>(graph: &G) -> Vec<Vec<VID>>
where
    G: StaticGraphViewOps,
{
    let mut index = 0;
    let mut stack = Vec::new();
    let mut indices: HashMap<VID, u64> = HashMap::new();
    let mut lowlink: HashMap<VID, u64> = HashMap::new();
    let mut on_stack: HashSet<VID> = HashSet::new();
    let mut result: Vec<Vec<VID>> = Vec::new();

    for node in (&graph).nodes() {
        if !indices.contains_key(&node.node) {
            tarjan(
                node,
                &mut index,
                &mut stack,
                &mut indices,
                &mut lowlink,
                &mut on_stack,
                &mut result,
            );
        }
    }
    result
}

/// Computes the strongly connected components of a graph using Tarjan's Strongly Connected Components algorithm
///
/// Original Paper:
/// https://web.archive.org/web/20170829214726id_/http://www.cs.ucsb.edu/~gilbert/cs240a/old/cs240aSpr2011/slides/TarjanDFS.pdf
///
/// # Arguments
///
/// - `graph` - A reference to the graph
///
/// # Returns
///
/// An [AlgorithmResult] containing the mapping from each node to its component ID
///
pub fn strongly_connected_components<G>(graph: &G) -> TypedNodeState<'static, SCCState, G>
where
    G: StaticGraphViewOps,
{
    let groups = tarjan_scc(graph);

    let mut values = vec![SCCState::default(); graph.unfiltered_num_nodes()];

    for (id, group) in groups.into_iter().enumerate() {
        for VID(node) in group {
            values[node] = SCCState { component_id: id };
        }
    }

    TypedNodeState::new(GenericNodeState::new_from_eval(graph.clone(), values, None))
}