Add experimental version of leiden_communities

_nx_cugraph/__init__.py

@@ -114,6 +114,7 @@
         "katz_centrality",
         "krackhardt_kite_graph",
         "ladder_graph",
+        "leiden_communities",
         "les_miserables_graph",
         "lollipop_graph",
         "louvain_communities",
@@ -234,6 +235,9 @@
         "katz_centrality": {
             "dtype : dtype or None, optional": "The data type (np.float32, np.float64, or None) to use for the edge weights in the algorithm. If None, then dtype is determined by the edge values.",
         },
+        "leiden_communities": {
+            "dtype : dtype or None, optional": "The data type (np.float32, np.float64, or None) to use for the edge weights in the algorithm. If None, then dtype is determined by the edge values.",
+        },
         "louvain_communities": {
             "dtype : dtype or None, optional": "The data type (np.float32, np.float64, or None) to use for the edge weights in the algorithm. If None, then dtype is determined by the edge values.",
         },

nx_cugraph/algorithms/community/__init__.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2023, NVIDIA CORPORATION.
+# Copyright (c) 2023-2024, 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
@@ -10,4 +10,5 @@
 # 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 .leiden import *
 from .louvain import *

nx_cugraph/algorithms/community/leiden.py

@@ -0,0 +1,52 @@
+# Copyright (c) 2024, 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.
+
+import numpy as np
+import pylibcugraph as plc
+
+from nx_cugraph.convert import _to_undirected_graph
+from nx_cugraph.utils import (
+    _dtype_param,
+    _get_float_dtype,
+    _groupby,
+    _seed_to_int,
+    networkx_algorithm,
+    not_implemented_for,
+)
+
+__all__ = ["leiden_communities"]
+
+
+@not_implemented_for("directed")
+@networkx_algorithm(extra_params=_dtype_param, version_added="25.02", _plc="leiden")
+def leiden_communities(
+    G, weight="weight", resolution=1, max_level=None, seed=None, *, dtype=None
+):
+    # Warning: this API is experimental and may change. It is not yet in NetworkX.
+    # See: https://github.com/networkx/networkx/pull/7743
+    seed = _seed_to_int(seed)
+    G = _to_undirected_graph(G, weight, 1, np.float32)
+    dtype = _get_float_dtype(dtype, graph=G, weight=weight)
+    if max_level is None or max_level < 0:
+        max_level = 500
+    node_ids, clusters, modularity = plc.leiden(
+        resource_handle=plc.ResourceHandle(),
+        random_state=seed,
+        graph=G._get_plc_graph(weight, 1, dtype),
+        max_level=max_level,
+        resolution=resolution,
+        theta=1,  # TODO: expose theta as a backend-only parameter once it's used
+        do_expensive_check=False,
+    )
+    groups = _groupby(clusters, node_ids, groups_are_canonical=True)
+    return [set(G._nodearray_to_list(ids)) for ids in groups.values()]

nx_cugraph/tests/test_leiden.py

@@ -0,0 +1,22 @@
+# Copyright (c) 2024, 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.
+
+import nx_cugraph as nxcg
+
+
+def test_leiden_karate():
+    # Basic smoke test; if something here changes, we want to know!
+    G = nxcg.karate_club_graph()
+    leiden = nxcg.community.leiden_communities(G, seed=123)
+    louvain = nxcg.community.louvain_communities(G, seed=123)
+    assert leiden == louvain