Add transitive_closure_dag function

docs/source/api/algorithm_functions/dag_algorithms.rst

@@ -14,3 +14,4 @@ DAG Algorithms
    rustworkx.layers
    rustworkx.transitive_reduction
    rustworkx.topological_generations
+   rustworkx.transitive_closure_dag

docs/source/api/algorithm_functions/traversal.rst

@@ -22,3 +22,4 @@ Traversal
    rustworkx.visit.BFSVisitor
    rustworkx.visit.DijkstraVisitor
    rustworkx.TopologicalSorter
+   rustworkx.descendants_at_distance

docs/source/api/pydigraph_api_functions.rst

@@ -58,3 +58,4 @@ the functions from the explicitly typed based on the data type.
    rustworkx.digraph_dijkstra_search
    rustworkx.digraph_node_link_json
    rustworkx.digraph_longest_simple_path
+   rustworkx.graph_descendants_at_distance

docs/source/api/pygraph_api_functions.rst

@@ -58,3 +58,4 @@ typed API based on the data type.
    rustworkx.graph_dijkstra_search
    rustworkx.graph_node_link_json
    rustworkx.graph_longest_simple_path
+   rustworkx.digraph_descendants_at_distance

releasenotes/notes/add-transitive-closure-dag-3fb45113d552f007.yaml

@@ -0,0 +1,16 @@
+---
+features:
+  - |
+    Added a new function ``descendants_at_distance`` to the rustworkx-core
+    crate under the ``traversal`` module
+  - |
+    Added a new function ``build_transitive_closure_dag`` to the rustworkx-core
+    crate under the ``traversal`` module.
+  - |
+    Added a new function, :func:`~.transitive_closure_dag`, which provides
+    an optimize method for computing the transitive closure of an input
+    DAG.
+  - |
+    Added a new function :func:`~.descendants_at_distance` which provides
+    a method to find the nodes at a fixed distance from a source in
+    a graph object.

rustworkx-core/src/traversal/descendants.rs

@@ -0,0 +1,44 @@
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+
+use hashbrown::HashSet;
+use petgraph::visit::{IntoNeighborsDirected, NodeCount, Visitable};
+
+/// Returns all nodes at a fixed `distance` from `source` in `G`.
+/// Args:
+///     `graph`:
+///     `source`:
+///     `distance`:
+pub fn descendants_at_distance<G>(graph: G, source: G::NodeId, distance: usize) -> Vec<G::NodeId>
+where
+    G: Visitable + IntoNeighborsDirected + NodeCount,
+    G::NodeId: std::cmp::Eq + std::hash::Hash,
+{
+    let mut current_layer: Vec<G::NodeId> = vec![source];
+    let mut layers: usize = 0;
+    let mut visited: HashSet<G::NodeId> = HashSet::with_capacity(graph.node_count());
+    visited.insert(source);
+    while !current_layer.is_empty() && layers < distance {
+        let mut next_layer: Vec<G::NodeId> = Vec::new();
+        for node in current_layer {
+            for child in graph.neighbors_directed(node, petgraph::Outgoing) {
+                if !visited.contains(&child) {
+                    visited.insert(child);
+                    next_layer.push(child);
+                }
+            }
+        }
+        current_layer = next_layer;
+        layers += 1;
+    }
+    current_layer
+}

rustworkx-core/src/traversal/mod.rs

@@ -13,9 +13,11 @@
 //! Module for graph traversal algorithms.
 
 mod bfs_visit;
+mod descendants;
 mod dfs_edges;
 mod dfs_visit;
 mod dijkstra_visit;
+mod transitive_closure;
 
 use petgraph::prelude::*;
 use petgraph::visit::GraphRef;
@@ -25,9 +27,11 @@ use petgraph::visit::VisitMap;
 use petgraph::visit::Visitable;
 
 pub use bfs_visit::{breadth_first_search, BfsEvent};
+pub use descendants::descendants_at_distance;
 pub use dfs_edges::dfs_edges;
 pub use dfs_visit::{depth_first_search, DfsEvent};
 pub use dijkstra_visit::{dijkstra_search, DijkstraEvent};
+pub use transitive_closure::build_transitive_closure_dag;
 
 /// Return if the expression is a break value, execute the provided statement
 /// if it is a prune value.

rustworkx-core/src/traversal/transitive_closure.rs

@@ -0,0 +1,83 @@
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+
+use petgraph::algo::{toposort, Cycle};
+use petgraph::data::Build;
+use petgraph::visit::{
+    GraphBase, IntoNeighborsDirected, IntoNodeIdentifiers, NodeCount, Visitable,
+};
+
+use crate::traversal::descendants_at_distance;
+
+/// Build a transitive closure out of a given DAG
+///
+/// This function will mutate a given DAG object (which is typically moved to
+/// this function) into a transitive closure of the graph and then returned.
+/// If you'd like to preserve the input graph pass a clone of the original graph.
+/// The transitive closure of :math:`G = (V, E)` is a graph :math:`G+ = (V, E+)`
+/// such that for all pairs of :math:`v, w` in :math:`V` there is an edge
+/// :math:`(v, w) in :math:`E+` if and only if there is a non-null path from
+/// :math:`v` to :math:`w` in :math:`G`. This funciton provides an optimized
+/// path for computing the the transitive closure of a DAG, if the input graph
+/// contains cycles it will error.
+///
+/// Arguments:
+///
+///  - `graph`: A mutable graph object representing the DAG
+///  - `topological_order`: An optional `Vec` of node identifiers representing
+///     the topological order to traverse the DAG with. If not specified the
+///     `petgraph::algo::toposort` function will be called to generate this
+///  - `default_edge_weight`: A callable function that takes no arguments and
+///     returns the `EdgeWeight` type object to use for each edge added to
+///     `graph
+///
+/// # Example
+///
+/// ```rust
+/// use rustworkx_core::traversal::build_transitive_closure_dag;
+///
+/// let g = petgraph::graph::DiGraph::<i32, i32>::from_edges(&[(0, 1, 0), (1, 2, 0), (2, 3, 0)]);
+///
+/// let res = build_transitive_closure_dag(g, None, || -> i32 {0});
+/// let out_graph = res.unwrap();
+/// let out_edges: Vec<(usize, usize)> = out_graph
+///     .edge_indices()
+///     .map(|e| {
+///         let endpoints = out_graph.edge_endpoints(e).unwrap();
+///         (endpoints.0.index(), endpoints.1.index())
+///     })
+///     .collect();
+/// assert_eq!(vec![(0, 1), (1, 2), (2, 3), (1, 3), (0, 3), (0, 2)], out_edges)
+/// ```
+pub fn build_transitive_closure_dag<'a, G, F>(
+    mut graph: G,
+    topological_order: Option<Vec<G::NodeId>>,
+    default_edge_weight: F,
+) -> Result<G, Cycle<G::NodeId>>
+where
+    G: NodeCount + Build + Clone,
+    for<'b> &'b G:
+        GraphBase<NodeId = G::NodeId> + Visitable + IntoNeighborsDirected + IntoNodeIdentifiers,
+    G::NodeId: std::cmp::Eq + std::hash::Hash,
+    F: Fn() -> G::EdgeWeight,
+{
+    let node_order: Vec<G::NodeId> = match topological_order {
+        Some(topo_order) => topo_order,
+        None => toposort(&graph, None)?,
+    };
+    for node in node_order.into_iter().rev() {
+        for descendant in descendants_at_distance(&graph, node, 2) {
+            graph.add_edge(node, descendant, default_edge_weight());
+        }
+    }
+    Ok(graph)
+}

rustworkx/__init__.py

@@ -1875,6 +1875,30 @@ def longest_simple_path(graph):
     """
 
 
+@_rustworkx_dispatch
+def descendants_at_distance(graph, source, distance):
+    """Returns all nodes at a fixed distance from ``source`` in ``graph``
+
+    :param graph: The graph to find the descendants in
+    :param int source: The node index to find the descendants from
+    :param int distance: The distance from ``source``
+
+    :returns: The node indices of the nodes ``distance`` from ``source`` in ``graph``.
+    :rtype: NodeIndices
+
+    For example::
+
+        import rustworkx as rx
+
+        graph = rx.generators.path_graph(5)
+        res = rx.descendants_at_distance(graph, 2, 2)
+        print(res)
+
+    will return: ``[0, 4]``
+    """
+    raise TypeError("Invalid Input Type %s for graph" % type(graph))
+
+
 @_rustworkx_dispatch
 def isolates(graph):
     """Return a list of isolates in a graph object
@@ -2006,3 +2030,4 @@ def all_shortest_paths(
 
     """
     raise TypeError("Invalid Input Type %s for graph" % type(graph))
+>>>>>>> origin/main

src/dag_algo/mod.rs

@@ -92,6 +92,8 @@ pub fn traversal_directions(reverse: bool) -> (petgraph::Direction, petgraph::Di
     }
 }
 
+use rustworkx_core::traversal;
+
 /// Find the longest path in a DAG
 ///
 /// :param PyDiGraph graph: The graph to find the longest path on. The input
@@ -597,6 +599,48 @@ pub fn collect_bicolor_runs(
     Ok(block_list)
 }
 
+/// Return the transitive closure of a directed acyclic graph
+///
+/// The transitive closure of :math:`G = (V, E)` is a graph :math:`G+ = (V, E+)`
+/// such that for all pairs of :math:`v, w` in :math:`V` there is an edge
+/// :math:`(v, w) in :math:`E+` if and only if there is a non-null path from
+/// :math:`v` to :math:`w` in :math:`G`.
+///
+/// :param PyDiGraph graph: The input DAG to compute the transitive closure of
+/// :param list topological_order: An optional topological order for ``graph``
+///     which represents the order the graph will be traversed in computing
+///     the transitive closure. If one is not provided (or it is explicitly
+///     set to ``None``) a topological order will be computed by this function.
+///
+/// :returns: The transitive closure of ``graph``
+/// :rtype: PyDiGraph
+///
+/// :raises DAGHasCycle: If the input ``graph`` is not acyclic
+#[pyfunction]
+#[pyo3(text_signature = "(graph, / topological_order=None)")]
+pub fn transitive_closure_dag(
+    py: Python,
+    graph: &digraph::PyDiGraph,
+    topological_order: Option<Vec<usize>>,
+) -> PyResult<digraph::PyDiGraph> {
+    let default_weight = || -> PyObject { py.None() };
+    match traversal::build_transitive_closure_dag(
+        graph.graph.clone(),
+        topological_order.map(|order| order.into_iter().map(NodeIndex::new).collect()),
+        default_weight,
+    ) {
+        Ok(out_graph) => Ok(digraph::PyDiGraph {
+            graph: out_graph,
+            cycle_state: algo::DfsSpace::default(),
+            check_cycle: false,
+            node_removed: false,
+            multigraph: true,
+            attrs: py.None(),
+        }),
+        Err(_err) => Err(DAGHasCycle::new_err("Topological Sort encountered a cycle")),
+    }
+}
+
 /// Returns the transitive reduction of a directed acyclic graph
 ///
 /// The transitive reduction of :math:`G = (V,E)` is a graph :math:`G\prime = (V,E\prime)`
@@ -612,7 +656,6 @@ pub fn collect_bicolor_runs(
 /// :rtype: Tuple[PyGraph, dict]
 ///
 /// :raises PyValueError: if ``graph`` is not a DAG
-
 #[pyfunction]
 #[pyo3(text_signature = "(graph, /)")]
 pub fn transitive_reduction(

src/lib.rs

@@ -614,6 +614,9 @@ fn rustworkx(py: Python<'_>, m: &Bound<PyModule>) -> PyResult<()> {
     m.add_wrapped(wrap_pyfunction!(read_graphml))?;
     m.add_wrapped(wrap_pyfunction!(digraph_node_link_json))?;
     m.add_wrapped(wrap_pyfunction!(graph_node_link_json))?;
+    m.add_wrapped(wrap_pyfunction!(transitive_closure_dag))?;
+    m.add_wrapped(wrap_pyfunction!(graph_descendants_at_distance))?;
+    m.add_wrapped(wrap_pyfunction!(digraph_descendants_at_distance))?;
     m.add_wrapped(wrap_pyfunction!(from_node_link_json_file))?;
     m.add_wrapped(wrap_pyfunction!(parse_node_link_json))?;
     m.add_wrapped(wrap_pyfunction!(pagerank))?;

src/traversal/mod.rs

@@ -21,7 +21,7 @@ use dijkstra_visit::{dijkstra_handler, PyDijkstraVisitor};
 use rustworkx_core::traversal::{
     ancestors as core_ancestors, bfs_predecessors as core_bfs_predecessors,
     bfs_successors as core_bfs_successors, breadth_first_search, depth_first_search,
-    descendants as core_descendants, dfs_edges, dijkstra_search,
+    descendants as core_descendants, descendants_at_distance, dfs_edges, dijkstra_search,
 };
 
 use super::{digraph, graph, iterators, CostFn};
@@ -773,3 +773,67 @@ pub fn graph_dijkstra_search(
 
     Ok(())
 }
+
+/// Returns all nodes at a fixed distance from ``source`` in ``graph``
+///
+/// :param PyGraph graph: The graph to find the descendants in
+/// :param int source: The node index to find the descendants from
+/// :param int distance: The distance from ``source``
+///
+/// :returns: The node indices of the nodes ``distance`` from ``source`` in ``graph``.
+/// :rtype: NodeIndices
+/// For example::
+///
+///     import rustworkx as rx
+///
+///     graph = rx.generators.path_graph(5)
+///     res = rx.descendants_at_distance(graph, 2, 2)
+///     print(res)
+///
+/// will return: ``[0, 4]``
+#[pyfunction]
+pub fn graph_descendants_at_distance(
+    graph: graph::PyGraph,
+    source: usize,
+    distance: usize,
+) -> iterators::NodeIndices {
+    let source = NodeIndex::new(source);
+    iterators::NodeIndices {
+        nodes: descendants_at_distance(&graph.graph, source, distance)
+            .into_iter()
+            .map(|x| x.index())
+            .collect(),
+    }
+}
+
+/// Returns all nodes at a fixed distance from ``source`` in ``graph``
+///
+/// :param PyDiGraph graph: The graph to find the descendants in
+/// :param int source: The node index to find the descendants from
+/// :param int distance: The distance from ``source``
+///
+/// :returns: The node indices of the nodes ``distance`` from ``source`` in ``graph``.
+/// :rtype: NodeIndices
+/// For example::
+///
+///     import rustworkx as rx
+///
+///     graph = rx.generators.directed_path_graph(5)
+///     res = rx.descendants_at_distance(graph, 2, 2)
+///     print(res)
+///
+/// will return: ``[4]``
+#[pyfunction]
+pub fn digraph_descendants_at_distance(
+    graph: digraph::PyDiGraph,
+    source: usize,
+    distance: usize,
+) -> iterators::NodeIndices {
+    let source = NodeIndex::new(source);
+    iterators::NodeIndices {
+        nodes: descendants_at_distance(&graph.graph, source, distance)
+            .into_iter()
+            .map(|x| x.index())
+            .collect(),
+    }
+}