nx-cugraph: add ZeroGraph for nx-compatibility (zero-code change)

python/nx-cugraph/_nx_cugraph/__init__.py

@@ -22,6 +22,7 @@
 
 $ python _nx_cugraph/__init__.py
 """
+import os
 
 from _nx_cugraph._version import __version__
 
@@ -293,12 +294,16 @@ def get_info():
 
     for key in info_keys:
         del d[key]
+
+    d["default_config"] = {
+        "zero": os.environ.get("NX_CUGRAPH_ZERO", "true").strip().lower() == "true",
+    }
     return d
 
 
 def _check_networkx_version():
-    import warnings
     import re
+    import warnings
 
     import networkx as nx
 

python/nx-cugraph/nx_cugraph/__init__.py

@@ -32,7 +32,15 @@
 from . import algorithms
 from .algorithms import *
 
+from .interface import BackendInterface
+
 from _nx_cugraph._version import __git_commit__, __version__
 from _nx_cugraph import _check_networkx_version
 
 _check_networkx_version()
+
+BackendInterface.Graph = classes.ZeroGraph
+BackendInterface.DiGraph = classes.ZeroDiGraph
+BackendInterface.MultiGraph = classes.ZeroMultiGraph
+BackendInterface.MultiDiGraph = classes.ZeroMultiDiGraph
+del BackendInterface

python/nx-cugraph/nx_cugraph/algorithms/core.py

@@ -58,7 +58,10 @@ def _(G):
 @networkx_algorithm(is_incomplete=True, version_added="23.12", _plc="k_truss_subgraph")
 def k_truss(G, k):
     if is_nx := isinstance(G, nx.Graph):
+        zero = isinstance(G, nxcg.ZeroGraph)
         G = nxcg.from_networkx(G, preserve_all_attrs=True)
+    else:
+        zero = False
     if nxcg.number_of_selfloops(G) > 0:
         if nx.__version__[:3] <= "3.2":
             exc_class = nx.NetworkXError
@@ -128,6 +131,7 @@ def k_truss(G, k):
         node_values,
         node_masks,
         key_to_id=key_to_id,
+        zero=zero,
     )
     new_graph.graph.update(G.graph)
     return new_graph

python/nx-cugraph/nx_cugraph/algorithms/operators/unary.py

@@ -23,6 +23,7 @@
 
 @networkx_algorithm(version_added="24.02")
 def complement(G):
+    zero = isinstance(G, nxcg.ZeroGraph)
     G = _to_graph(G)
     N = G._N
     # Upcast to int64 so indices don't overflow.
@@ -43,6 +44,7 @@ def complement(G):
         src_indices.astype(index_dtype),
         dst_indices.astype(index_dtype),
         key_to_id=G.key_to_id,
+        zero=zero,
     )
 
 
@@ -51,10 +53,16 @@ def reverse(G, copy=True):
     if not G.is_directed():
         raise nx.NetworkXError("Cannot reverse an undirected graph.")
     if isinstance(G, nx.Graph):
-        if not copy:
+        zero = isinstance(G, nxcg.ZeroGraph)
+        if not copy and not zero:
             raise RuntimeError(
                 "Using `copy=False` is invalid when using a NetworkX graph "
                 "as input to `nx_cugraph.reverse`"
             )
         G = nxcg.from_networkx(G, preserve_all_attrs=True)
-    return G.reverse(copy=copy)
+    else:
+        zero = False
+    rv = G.reverse(copy=copy)
+    if zero:
+        return rv.to_zero()
+    return rv

python/nx-cugraph/nx_cugraph/algorithms/traversal/breadth_first_search.py

@@ -132,13 +132,15 @@ def bfs_tree(G, source, reverse=False, depth_limit=None, sort_neighbors=None):
         raise NotImplementedError(
             "sort_neighbors argument in bfs_tree is not currently supported"
         )
+    zero = isinstance(G, nxcg.ZeroGraph)
     G = _check_G_and_source(G, source)
     if depth_limit is not None and depth_limit < 1:
         return nxcg.DiGraph.from_coo(
             1,
             cp.array([], dtype=index_dtype),
             cp.array([], dtype=index_dtype),
             id_to_key=[source],
+            zero=zero,
         )
 
     distances, predecessors, node_ids = _bfs(
@@ -153,6 +155,7 @@ def bfs_tree(G, source, reverse=False, depth_limit=None, sort_neighbors=None):
             cp.array([], dtype=index_dtype),
             cp.array([], dtype=index_dtype),
             id_to_key=[source],
+            zero=zero,
         )
     # TODO: create renumbering helper function(s)
     unique_node_ids = cp.unique(cp.hstack((predecessors, node_ids)))
@@ -175,6 +178,7 @@ def bfs_tree(G, source, reverse=False, depth_limit=None, sort_neighbors=None):
         src_indices,
         dst_indices,
         key_to_id=key_to_id,
+        zero=zero,
     )
 
 

python/nx-cugraph/nx_cugraph/classes/__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
@@ -10,6 +10,7 @@
 # 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 .zero import ZeroGraph, ZeroDiGraph, ZeroMultiGraph, ZeroMultiDiGraph
 from .graph import Graph
 from .digraph import DiGraph
 from .multigraph import MultiGraph

python/nx-cugraph/nx_cugraph/classes/digraph.py

@@ -23,6 +23,7 @@
 
 from ..utils import index_dtype
 from .graph import Graph
+from .zero import ZeroDiGraph
 
 if TYPE_CHECKING:  # pragma: no cover
     from nx_cugraph.typing import AttrKey
@@ -46,6 +47,10 @@ def is_directed(cls) -> bool:
     def to_networkx_class(cls) -> type[nx.DiGraph]:
         return nx.DiGraph
 
+    @classmethod
+    def to_zero_class(cls) -> type[ZeroDiGraph]:
+        return ZeroDiGraph
+
     @networkx_api
     def size(self, weight: AttrKey | None = None) -> int:
         if weight is not None:
@@ -162,6 +167,7 @@ def to_undirected(self, reciprocal=False, as_view=False):
             node_masks,
             key_to_id=key_to_id,
             id_to_key=id_to_key,
+            zero=False,
         )
         if as_view:
             rv.graph = self.graph

python/nx-cugraph/nx_cugraph/classes/graph.py

@@ -24,6 +24,7 @@
 import nx_cugraph as nxcg
 
 from ..utils import index_dtype
+from .zero import ZeroGraph
 
 if TYPE_CHECKING:  # pragma: no cover
     from collections.abc import Iterable, Iterator
@@ -109,6 +110,7 @@ def from_coo(
         *,
         key_to_id: dict[NodeKey, IndexValue] | None = None,
         id_to_key: list[NodeKey] | None = None,
+        zero: bool | None = None,
         **attr,
     ) -> Graph:
         new_graph = object.__new__(cls)
@@ -173,7 +175,8 @@ def from_coo(
         isolates = nxcg.algorithms.isolate._isolates(new_graph)
         if len(isolates) > 0:
             new_graph._node_ids = cp.arange(new_graph._N, dtype=index_dtype)
-
+        if zero or zero is None and nx.config.backends.cugraph.zero:
+            new_graph = new_graph.to_zero()
         return new_graph
 
     @classmethod
@@ -188,6 +191,7 @@ def from_csr(
         *,
         key_to_id: dict[NodeKey, IndexValue] | None = None,
         id_to_key: list[NodeKey] | None = None,
+        zero: bool | None = None,
         **attr,
     ) -> Graph:
         N = indptr.size - 1
@@ -205,6 +209,7 @@ def from_csr(
             node_masks,
             key_to_id=key_to_id,
             id_to_key=id_to_key,
+            zero=zero,
             **attr,
         )
 
@@ -220,6 +225,7 @@ def from_csc(
         *,
         key_to_id: dict[NodeKey, IndexValue] | None = None,
         id_to_key: list[NodeKey] | None = None,
+        zero: bool | None = None,
         **attr,
     ) -> Graph:
         N = indptr.size - 1
@@ -237,6 +243,7 @@ def from_csc(
             node_masks,
             key_to_id=key_to_id,
             id_to_key=id_to_key,
+            zero=zero,
             **attr,
         )
 
@@ -254,6 +261,7 @@ def from_dcsr(
         *,
         key_to_id: dict[NodeKey, IndexValue] | None = None,
         id_to_key: list[NodeKey] | None = None,
+        zero: bool | None = None,
         **attr,
     ) -> Graph:
         src_indices = cp.array(
@@ -270,6 +278,7 @@ def from_dcsr(
             node_masks,
             key_to_id=key_to_id,
             id_to_key=id_to_key,
+            zero=zero,
             **attr,
         )
 
@@ -287,6 +296,7 @@ def from_dcsc(
         *,
         key_to_id: dict[NodeKey, IndexValue] | None = None,
         id_to_key: list[NodeKey] | None = None,
+        zero: bool | None = None,
         **attr,
     ) -> Graph:
         dst_indices = cp.array(
@@ -303,13 +313,14 @@ def from_dcsc(
             node_masks,
             key_to_id=key_to_id,
             id_to_key=id_to_key,
+            zero=zero,
             **attr,
         )
 
     def __new__(cls, incoming_graph_data=None, **attr) -> Graph:
         if incoming_graph_data is None:
             new_graph = cls.from_coo(
-                0, cp.empty(0, index_dtype), cp.empty(0, index_dtype)
+                0, cp.empty(0, index_dtype), cp.empty(0, index_dtype), zero=False
             )
         elif incoming_graph_data.__class__ is cls:
             new_graph = incoming_graph_data.copy()
@@ -318,6 +329,7 @@ def __new__(cls, incoming_graph_data=None, **attr) -> Graph:
         else:
             raise NotImplementedError
         new_graph.graph.update(attr)
+        # XXX: we could return ZeroGraph here, but let's not for now
         return new_graph
 
     #################
@@ -348,6 +360,10 @@ def to_networkx_class(cls) -> type[nx.Graph]:
     def to_undirected_class(cls) -> type[Graph]:
         return Graph
 
+    @classmethod
+    def to_zero_class(cls) -> type[ZeroGraph]:
+        return ZeroGraph
+
     ##############
     # Properties #
     ##############
@@ -542,6 +558,11 @@ def to_undirected(self, as_view: bool = False) -> Graph:
         # Does deep copy in networkx
         return self._copy(as_view, self.to_undirected_class())
 
+    def to_zero(self) -> ZeroGraph:
+        rv = self.to_zero_class()()
+        rv._cugraph = self
+        return rv
+
     # Not implemented...
     # adj, adjacency, add_edge, add_edges_from, add_node,
     # add_nodes_from, add_weighted_edges_from, degree,
@@ -593,6 +614,7 @@ def _copy(self, as_view: bool, cls: type[Graph], reverse: bool = False):
             node_masks,
             key_to_id=key_to_id,
             id_to_key=id_to_key,
+            zero=False,
         )
         if as_view:
             rv.graph = self.graph

python/nx-cugraph/nx_cugraph/classes/multidigraph.py

@@ -18,6 +18,7 @@
 
 from .digraph import DiGraph
 from .multigraph import MultiGraph
+from .zero import ZeroMultiDiGraph
 
 __all__ = ["MultiDiGraph"]
 
@@ -34,6 +35,10 @@ def is_directed(cls) -> bool:
     def to_networkx_class(cls) -> type[nx.MultiDiGraph]:
         return nx.MultiDiGraph
 
+    @classmethod
+    def to_zero_class(cls) -> type[ZeroMultiDiGraph]:
+        return ZeroMultiDiGraph
+
     ##########################
     # NetworkX graph methods #
     ##########################