nx-cugraph: add weakly connected components (PLC needs updated!)

python/nx-cugraph/_nx_cugraph/__init__.py

@@ -70,6 +70,7 @@
         "in_degree_centrality",
         "is_connected",
         "is_isolate",
+        "is_weakly_connected",
         "isolates",
         "k_truss",
         "karate_club_graph",
@@ -85,6 +86,7 @@
         "number_connected_components",
         "number_of_isolates",
         "number_of_selfloops",
+        "number_weakly_connected_components",
         "octahedral_graph",
         "out_degree_centrality",
         "pagerank",
@@ -102,6 +104,7 @@
         "truncated_tetrahedron_graph",
         "turan_graph",
         "tutte_graph",
+        "weakly_connected_components",
         "wheel_graph",
         # END: functions
     },

python/nx-cugraph/nx_cugraph/algorithms/components/__init__.py

@@ -11,3 +11,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from .connected import *
+from .weakly_connected import *

python/nx-cugraph/nx_cugraph/algorithms/components/connected.py

@@ -32,6 +32,11 @@
 @not_implemented_for("directed")
 @networkx_algorithm
 def number_connected_components(G):
+    G = _to_undirected_graph(G)
+    return _number_connected_components(G)
+
+
+def _number_connected_components(G):
     return sum(1 for _ in connected_components(G))
     # PREFERRED IMPLEMENTATION, BUT PLC DOES NOT HANDLE ISOLATED VERTICES WELL
     # G = _to_undirected_graph(G)
@@ -60,6 +65,10 @@ def _(G):
 @networkx_algorithm
 def connected_components(G):
     G = _to_undirected_graph(G)
+    return _connected_components(G)
+
+
+def _connected_components(G):
     if G.src_indices.size == 0:
         # TODO: PLC doesn't handle empty graphs (or isolated nodes) gracefully!
         return [{key} for key in G._nodeiter_to_iter(range(len(G)))]
@@ -89,6 +98,10 @@ def connected_components(G):
 @networkx_algorithm
 def is_connected(G):
     G = _to_undirected_graph(G)
+    return _is_connected(G)
+
+
+def _is_connected(G):
     if len(G) == 0:
         raise nx.NetworkXPointlessConcept(
             "Connectivity is undefined for the null graph."

python/nx-cugraph/nx_cugraph/algorithms/components/weakly_connected.py

@@ -0,0 +1,49 @@
+# Copyright (c) 2023, NVIDIA CORPORATION.
+# 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.
+
+
+from nx_cugraph.convert import _to_directed_graph
+from nx_cugraph.utils import networkx_algorithm, not_implemented_for
+
+from .connected import (
+    _connected_components,
+    _is_connected,
+    _number_connected_components,
+)
+
+__all__ = [
+    "number_weakly_connected_components",
+    "weakly_connected_components",
+    "is_weakly_connected",
+]
+
+
+@not_implemented_for("undirected")
+@networkx_algorithm
+def weakly_connected_components(G):
+    G = _to_directed_graph(G)
+    return _connected_components(G)
+
+
+@not_implemented_for("undirected")
+@networkx_algorithm
+def number_weakly_connected_components(G):
+    G = _to_directed_graph(G)
+    return _number_connected_components(G)
+
+
+@not_implemented_for("undirected")
+@networkx_algorithm
+def is_weakly_connected(G):
+    G = _to_directed_graph(G)
+    return _is_connected(G)