Initial commit.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -1,7 +1,6 @@
-# The SPQR-Tree algorithm implementation.
+# The SQPR-Tree algorithm implementation.
-# Copyright 2026 imacat.  All rights reserved.
+# Copyright 2026 DSP, inc.  All rights reserved.
-# Authors:
+# Author: imacat@mail.imacat.idv.tw (imacat), 2026/3/1
-#   imacat@mail.imacat.idv.tw (imacat), 2026/3/1
 
 *.pyc
 __pycache__

MANIFEST.in

@@ -17,6 +17,6 @@
 #  limitations under the License.
 
 recursive-include docs *
-prune docs/build
+recursive-exclude docs/build *
 recursive-include tests *
 recursive-exclude tests *.pyc

docs/source/changelog.rst

@@ -1,22 +1,3 @@
 Change Log
 ==========
 
-
-Version 0.1.1
--------------
-
-Released 2026/3/11
-
-- ``find_triconnected_components()`` now raises ``ValueError`` when
-  the input graph is not biconnected (disconnected or has a cut
-  vertex).  Previously, non-biconnected input was silently accepted
-  and produced incorrect results.
-- Use public API imports in documentation examples.
-
-
-Version 0.1.0
--------------
-
-Released 2026/3/5
-
-Initial release.

docs/source/intro.rst

@@ -133,11 +133,12 @@ Using a MultiGraph
 ~~~~~~~~~~~~~~~~~~
 
 For more control, build a
-:class:`~spqrtree.MultiGraph` directly:
+:class:`~spqrtree._graph.MultiGraph` directly:
 
 .. code-block:: python
 
-   from spqrtree import MultiGraph, SPQRTree
+   from spqrtree._graph import MultiGraph
+   from spqrtree import SPQRTree
 
    g = MultiGraph()
    g.add_edge(0, 1)

pyproject.toml

@@ -3,7 +3,7 @@
 #   imacat@mail.imacat.idv.tw (imacat), 2026/3/2
 # AI assistance: Claude Code (Anthropic)
 
-#  Copyright (c) 2026 imacat.
+#  Copyright (c) 2022-2026 imacat.
 #
 #  Licensed under the Apache License, Version 2.0 (the "License");
 #  you may not use this file except in compliance with the License.
@@ -53,13 +53,6 @@ classifiers = [
     "Typing :: Typed",
 ]
 
-[project.urls]
-Homepage = "https://github.com/imacat/spqrtree"
-Repository = "https://github.com/imacat/spqrtree"
-Documentation = "https://spqrtree.readthedocs.io"
-"Change Log" = "https://spqrtree.readthedocs.io/en/latest/changelog.html"
-"Bug Tracker" = "https://github.com/imacat/spqrtree/issues"
-
 [build-system]
 requires = ["setuptools>=61"]
 build-backend = "setuptools.build_meta"

src/spqrtree/__init__.py

@@ -25,11 +25,11 @@ Di Battista & Tamassia (1996).
 
 Public API::
 
+    from spqrtree import SPQRTree, SPQRNode, NodeType
     from spqrtree import Edge, MultiGraph
-    from spqrtree import NodeType, SPQRNode, build_spqr_tree
+    from spqrtree import build_spqr_tree
     from spqrtree import (
-        ComponentType,
+        ComponentType, TriconnectedComponent,
-        TriconnectedComponent,
         find_triconnected_components,
     )
 """
@@ -43,7 +43,7 @@ from spqrtree._triconnected import (
     find_triconnected_components,
 )
 
-VERSION: str = "0.1.1"
+VERSION: str = "0.0.0"
 """The package version."""
 __all__: list[str] = [
     "SPQRTree", "SPQRNode", "NodeType",

src/spqrtree/_triconnected.py

@@ -92,41 +92,6 @@ class TriconnectedComponent:
     """All edges in this component (real and virtual)."""
 
 
-def _check_biconnected(graph: MultiGraph) -> None:
-    """Check that a graph is biconnected (connected with no cut vertex).
-
-    Uses a single DFS pass to verify connectivity and detect cut
-    vertices via Tarjan's algorithm.  A non-root vertex v is a cut
-    vertex if it has a child w such that lowpt1[w] >= dfs_num[v].
-    The DFS root is a cut vertex if it has two or more children.
-
-    :param graph: The multigraph to check.
-    :raises ValueError: If the graph is not connected or has a cut
-        vertex.
-    """
-    start: Hashable = next(iter(graph.vertices))
-    pt: PalmTree = build_palm_tree(graph, start)
-
-    # Check connectivity: DFS must visit all vertices.
-    if len(pt.dfs_num) < graph.num_vertices():
-        raise ValueError("graph is not connected")
-
-    # Check for cut vertices.
-    for v in graph.vertices:
-        if pt.parent[v] is None:
-            # Root: cut vertex if it has 2+ children.
-            if len(pt.children[v]) >= 2:
-                raise ValueError("graph has a cut vertex")
-        else:
-            # Non-root: cut vertex if any child w has
-            # lowpt1[w] >= dfs_num[v].
-            v_num: int = pt.dfs_num[v]
-            for w in pt.children[v]:
-                if pt.lowpt1[w] >= v_num:
-                    raise ValueError(
-                        "graph has a cut vertex")
-
-
 def find_triconnected_components(
     graph: MultiGraph,
 ) -> list[TriconnectedComponent]:
@@ -143,14 +108,10 @@ def find_triconnected_components(
 
     :param graph: A biconnected multigraph.
     :return: A list of TriconnectedComponent objects.
-    :raises ValueError: If the graph is not connected or has a
-        cut vertex.
     """
     if graph.num_vertices() == 0 or graph.num_edges() == 0:
         return []
 
-    _check_biconnected(graph)
-
     # Work on a copy to avoid modifying the caller's graph.
     g: MultiGraph = graph.copy()
 

tests/test_graph.py

@@ -20,7 +20,7 @@
 import unittest
 from collections.abc import Hashable
 
-from spqrtree import Edge, MultiGraph
+from spqrtree._graph import Edge, MultiGraph
 
 
 class TestEdge(unittest.TestCase):

tests/test_palm_tree.py

@@ -24,7 +24,7 @@ DFS from vertex 1.  Edge insertion order is specified in each test.
 import unittest
 from collections.abc import Hashable
 
-from spqrtree import Edge, MultiGraph
+from spqrtree._graph import Edge, MultiGraph
 from spqrtree._palm_tree import PalmTree, build_palm_tree, phi_key
 
 

tests/test_spqrtree.py

@@ -26,13 +26,8 @@ import unittest
 from collections import deque
 from collections.abc import Hashable
 
-from spqrtree import (
+from spqrtree._graph import Edge, MultiGraph
-    Edge,
+from spqrtree._spqr import NodeType, SPQRNode, build_spqr_tree
-    MultiGraph,
-    NodeType,
-    SPQRNode,
-    build_spqr_tree,
-)
 
 
 def _make_k3() -> MultiGraph:
@@ -2856,38 +2851,3 @@ class TestSPQRRpstFig1a(unittest.TestCase):
     def test_no_adjacent_p_nodes(self) -> None:
         """Test that no P-node is adjacent to another P-node."""
         _assert_no_ss_pp(self, self.root, NodeType.P)
-
-
-class TestBuildSpqrTreeBiconnectivity(unittest.TestCase):
-    """Tests that build_spqr_tree rejects non-biconnected graphs."""
-
-    def test_cut_vertex_raises(self) -> None:
-        """Test that a graph with a cut vertex raises ValueError."""
-        g: MultiGraph = MultiGraph()
-        g.add_edge(1, 2)
-        g.add_edge(2, 3)
-        g.add_edge(1, 3)
-        g.add_edge(3, 4)
-        g.add_edge(4, 5)
-        g.add_edge(3, 5)
-        with self.assertRaises(ValueError) as ctx:
-            build_spqr_tree(g)
-        self.assertIn("cut vertex", str(ctx.exception))
-
-    def test_disconnected_raises(self) -> None:
-        """Test that a disconnected graph raises ValueError."""
-        g: MultiGraph = MultiGraph()
-        g.add_edge(1, 2)
-        g.add_edge(3, 4)
-        with self.assertRaises(ValueError) as ctx:
-            build_spqr_tree(g)
-        self.assertIn("not connected", str(ctx.exception))
-
-    def test_path_raises(self) -> None:
-        """Test that a path graph raises ValueError."""
-        g: MultiGraph = MultiGraph()
-        g.add_edge(1, 2)
-        g.add_edge(2, 3)
-        with self.assertRaises(ValueError) as ctx:
-            build_spqr_tree(g)
-        self.assertIn("cut vertex", str(ctx.exception))

tests/test_triconnected.py

@@ -25,10 +25,9 @@ edge appearance count.
 import unittest
 from collections.abc import Hashable
 
-from spqrtree import (
+from spqrtree._graph import Edge, MultiGraph
+from spqrtree._triconnected import (
     ComponentType,
-    Edge,
-    MultiGraph,
     TriconnectedComponent,
     find_triconnected_components,
 )
@@ -2786,88 +2785,3 @@ class TestTriconnectedRpstFig1a(unittest.TestCase):
     def test_all_invariants(self) -> None:
         """Test all decomposition invariants."""
         _check_all_invariants(self, self.g, self.comps)
-
-
-def _make_cut_vertex_graph() -> MultiGraph:
-    """Build a graph with a cut vertex.
-
-    Graph: 1-2-3 triangle connected to 3-4-5 triangle via
-    shared vertex 3 (the cut vertex).
-
-    :return: A MultiGraph with a cut vertex at vertex 3.
-    """
-    g: MultiGraph = MultiGraph()
-    g.add_edge(1, 2)
-    g.add_edge(2, 3)
-    g.add_edge(1, 3)
-    g.add_edge(3, 4)
-    g.add_edge(4, 5)
-    g.add_edge(3, 5)
-    return g
-
-
-def _make_disconnected_graph() -> MultiGraph:
-    """Build a disconnected graph with two components.
-
-    Component 1: edge 1-2.
-    Component 2: edge 3-4.
-
-    :return: A disconnected MultiGraph.
-    """
-    g: MultiGraph = MultiGraph()
-    g.add_edge(1, 2)
-    g.add_edge(3, 4)
-    return g
-
-
-def _make_path_graph() -> MultiGraph:
-    """Build a path graph 1-2-3 (not biconnected).
-
-    Vertex 2 is a cut vertex (removing it disconnects 1 and 3).
-
-    :return: A MultiGraph representing a path.
-    """
-    g: MultiGraph = MultiGraph()
-    g.add_edge(1, 2)
-    g.add_edge(2, 3)
-    return g
-
-
-class TestBiconnectivityCheck(unittest.TestCase):
-    """Tests that non-biconnected graphs raise ValueError."""
-
-    def test_cut_vertex_raises(self) -> None:
-        """Test that a graph with a cut vertex raises ValueError."""
-        g: MultiGraph = _make_cut_vertex_graph()
-        with self.assertRaises(ValueError) as ctx:
-            find_triconnected_components(g)
-        self.assertIn("cut vertex", str(ctx.exception))
-
-    def test_disconnected_raises(self) -> None:
-        """Test that a disconnected graph raises ValueError."""
-        g: MultiGraph = _make_disconnected_graph()
-        with self.assertRaises(ValueError) as ctx:
-            find_triconnected_components(g)
-        self.assertIn("not connected", str(ctx.exception))
-
-    def test_path_raises(self) -> None:
-        """Test that a path graph (has cut vertex) raises ValueError."""
-        g: MultiGraph = _make_path_graph()
-        with self.assertRaises(ValueError) as ctx:
-            find_triconnected_components(g)
-        self.assertIn("cut vertex", str(ctx.exception))
-
-    def test_single_vertex_no_edges(self) -> None:
-        """Test that a single vertex with no edges returns empty."""
-        g: MultiGraph = MultiGraph()
-        g.add_vertex(1)
-        comps: list[TriconnectedComponent] = \
-            find_triconnected_components(g)
-        self.assertEqual(comps, [])
-
-    def test_biconnected_graph_ok(self) -> None:
-        """Test that a biconnected graph does not raise."""
-        g: MultiGraph = _make_k3()
-        comps: list[TriconnectedComponent] = \
-            find_triconnected_components(g)
-        self.assertEqual(len(comps), 1)