d36e2b88d6
This assumes that the set of valid node IDs is exactly `0..num_nodes`. In practice, we have a lot of graph-algorithm code that already assumes that nodes are densely numbered, by using `num_nodes` to allocate per-node indexed data structures.
98 lines
2.8 KiB
Rust
98 lines
2.8 KiB
Rust
use rustc_index::Idx;
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pub mod dominators;
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pub mod implementation;
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pub mod iterate;
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mod reference;
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pub mod reversed;
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pub mod scc;
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pub mod vec_graph;
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#[cfg(test)]
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mod tests;
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pub trait DirectedGraph {
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type Node: Idx;
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/// Returns the total number of nodes in this graph.
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///
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/// Several graph algorithm implementations assume that every node ID is
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/// strictly less than the number of nodes, i.e. nodes are densely numbered.
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/// That assumption allows them to use `num_nodes` to allocate per-node
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/// data structures, indexed by node.
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fn num_nodes(&self) -> usize;
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/// Iterates over all nodes of a graph in ascending numeric order.
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///
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/// Assumes that nodes are densely numbered, i.e. every index in
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/// `0..num_nodes` is a valid node.
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fn iter_nodes(
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&self,
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) -> impl Iterator<Item = Self::Node> + DoubleEndedIterator + ExactSizeIterator {
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(0..self.num_nodes()).map(<Self::Node as Idx>::new)
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}
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}
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pub trait NumEdges: DirectedGraph {
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fn num_edges(&self) -> usize;
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}
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pub trait StartNode: DirectedGraph {
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fn start_node(&self) -> Self::Node;
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}
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pub trait Successors: DirectedGraph {
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fn successors(&self, node: Self::Node) -> impl Iterator<Item = Self::Node>;
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}
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pub trait Predecessors: DirectedGraph {
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fn predecessors(&self, node: Self::Node) -> impl Iterator<Item = Self::Node>;
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}
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/// Alias for [`DirectedGraph`] + [`StartNode`] + [`Predecessors`] + [`Successors`].
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pub trait ControlFlowGraph: DirectedGraph + StartNode + Predecessors + Successors {}
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impl<T> ControlFlowGraph for T where T: DirectedGraph + StartNode + Predecessors + Successors {}
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/// Returns `true` if the graph has a cycle that is reachable from the start node.
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pub fn is_cyclic<G>(graph: &G) -> bool
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where
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G: ?Sized + DirectedGraph + StartNode + Successors,
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{
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iterate::TriColorDepthFirstSearch::new(graph)
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.run_from_start(&mut iterate::CycleDetector)
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.is_some()
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}
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pub fn depth_first_search<G>(graph: G, from: G::Node) -> iterate::DepthFirstSearch<G>
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where
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G: Successors,
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{
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iterate::DepthFirstSearch::new(graph).with_start_node(from)
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}
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pub fn depth_first_search_as_undirected<G>(
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graph: G,
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from: G::Node,
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) -> iterate::DepthFirstSearch<impl Successors<Node = G::Node>>
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where
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G: Successors + Predecessors,
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{
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struct AsUndirected<G>(G);
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impl<G: DirectedGraph> DirectedGraph for AsUndirected<G> {
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type Node = G::Node;
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fn num_nodes(&self) -> usize {
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self.0.num_nodes()
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}
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}
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impl<G: Successors + Predecessors> Successors for AsUndirected<G> {
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fn successors(&self, node: Self::Node) -> impl Iterator<Item = Self::Node> {
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self.0.successors(node).chain(self.0.predecessors(node))
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}
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}
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iterate::DepthFirstSearch::new(AsUndirected(graph)).with_start_node(from)
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}
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