def k_core(G,
k=None,
core_number=None):
"""
Compute the k-core of the graph G based on the out degree of its nodes. A
k-core of a graph is a maximal subgraph that contains nodes of degree k or
more. This call does not support a graph with self-loops and parallel
edges.
Parameters
----------
G : cuGraph.Graph
cuGraph graph descriptor with connectivity information. The graph
should contain undirected edges where undirected edges are represented
as directed edges in both directions. While this graph can contain edge
weights, they don't participate in the calculation of the k-core.
k : int, optional
Order of the core. This value must not be negative. If set to None, the
main core is returned.
core_number : cudf.DataFrame, optional
Precomputed core number of the nodes of the graph G containing two
cudf.Series of size V: the vertex identifiers and the corresponding
core number values. If set to None, the core numbers of the nodes are
calculated internally.
core_number['vertex'] : cudf.Series
Contains the vertex identifiers
core_number['values'] : cudf.Series
Contains the core number of vertices
Returns
-------
KCoreGraph : cuGraph.Graph
K Core of the input graph
Examples
--------
>>> M = cudf.read_csv('datasets/karate.csv', delimiter=' ',
>>> dtype=['int32', 'int32', 'float32'], header=None)
>>> sources = cudf.Series(M['0'])
>>> destinations = cudf.Series(M['1'])
>>> G = cugraph.Graph()
>>> G.add_edge_list(sources, destinations, None)
>>> KCoreGraph = cugraph.k_core(G)
"""
KCoreGraph = DiGraph()
if core_number is None:
core_number = core_number_wrapper.core_number(G)
core_number = core_number.rename(columns={"core_number": "values"})
if k is None:
k = core_number['values'].max()
k_core_wrapper.k_core(G,
KCoreGraph,
k,
core_number)
return KCoreGraph
def from_cudf_edgelist(df,
source='source',
destination='destination',
edge_attr=None,
create_using=Graph,
renumber=True):
"""
Return a new graph created from the edge list representaion. This function
is added for NetworkX compatibility (this function is a RAPIDS version of
NetworkX's from_pandas_edge_list()). This function does not support
multiple source or destination columns. But does support renumbering
Parameters
----------
df : cudf.DataFrame
This cudf.DataFrame contains columns storing edge source vertices,
destination (or target following NetworkX's terminology) vertices, and
(optional) weights.
source : string or integer
This is used to index the source column.
destination : string or integer
This is used to index the destination (or target following NetworkX's
terminology) column.
edge_attr : string or integer, optional
This pointer can be ``None``. If not, this is used to index the weight
column.
create_using : cuGraph.Graph
Specify the type of Graph to create. Default is cugraph.Graph
renumber : bool
If source and destination indices are not in range 0 to V where V
is number of vertices, renumber argument should be True.
Examples
--------
>>> M = cudf.read_csv('datasets/karate.csv', delimiter=' ',
>>> dtype=['int32', 'int32', 'float32'], header=None)
>>> G = cugraph.Graph()
>>> G = cugraph.from_cudf_edgelist(M, source='0', target='1', weight='2')
"""
if create_using is Graph:
G = Graph()
elif create_using is DiGraph:
G = DiGraph()
else:
raise Exception("create_using supports Graph and DiGraph")
G.from_cudf_edgelist(df,
source=source,
destination=destination,
edge_attr=edge_attr,
renumber=renumber)
return G
def from_numpy_matrix(A, create_using=Graph):
"""
Initializes the graph from numpy matrix containing adjacency matrix.
Set create_using to cugraph.DiGraph for directed graph and
cugraph.Graph for undirected Graph.
"""
if create_using is Graph:
G = Graph()
elif create_using is DiGraph:
G = DiGraph()
else:
raise Exception("create_using supports Graph and DiGraph")
G.from_numpy_matrix(A)
return G
def from_pandas_adjacency(df, create_using=Graph):
"""
Initializes the graph from pandas adjacency matrix.
Set create_using to cugraph.DiGraph for directed graph and
cugraph.Graph for undirected Graph.
"""
if create_using is Graph:
G = Graph()
elif create_using is DiGraph:
G = DiGraph()
else:
raise Exception("create_using supports Graph and DiGraph")
G.from_pandas_adjacency(df)
return G
def from_cudf_edgelist(df,
source='source',
destination='destination',
edge_attr=None,
create_using=Graph,
renumber=True):
"""
Return a new graph created from the edge list representaion. This function
is added for NetworkX compatibility (this function is a RAPIDS version of
NetworkX's from_pandas_edge_list()).
Parameters
----------
df : cudf.DataFrame
This cudf.DataFrame contains columns storing edge source vertices,
destination (or target following NetworkX's terminology) vertices, and
(optional) weights.
source : string or integer
This is used to index the source column.
target : string or integer
This is used to index the destination (or target following NetworkX's
terminology) column.
weight : string or integer, optional
This pointer can be ``None``. If not, this is used to index the weight
column.
Examples
--------
>>> M = cudf.read_csv('datasets/karate.csv', delimiter=' ',
>>> dtype=['int32', 'int32', 'float32'], header=None)
>>> G = cugraph.Graph()
>>> G = cugraph.from_cudf_edgelist(M, source='0', target='1', weight='2')
"""
if create_using is Graph:
G = Graph()
elif create_using is DiGraph:
G = DiGraph()
else:
raise Exception("create_using supports Graph and DiGraph")
G.from_cudf_edgelist(df,
source=source,
destination=destination,
edge_attr=edge_attr,
renumber=renumber)
return G
def subgraph(G, vertices):
"""
Compute a subgraph of the existing graph including only the specified
vertices. This algorithm works for both directed and undirected graphs,
it does not actually traverse the edges, simply pulls out any edges that
are incident on vertices that are both contained in the vertices list.
Parameters
----------
G : cugraph.Graph
cuGraph graph descriptor
vertices : cudf.Series
Specifies the vertices of the induced subgraph
Returns
-------
Sg : cugraph.Graph
A graph object containing the subgraph induced by the given vertex set.
Examples
--------
>>> M = cudf.read_csv('datasets/karate.csv', delimiter=' ',
>>> dtype=['int32', 'int32', 'float32'], header=None)
>>> sources = cudf.Series(M['0'])
>>> destinations = cudf.Series(M['1'])
>>> G = cugraph.Graph()
>>> G.add_edge_list(sources, destinations, None)
>>> verts = numpy.zeros(3, dtype=numpy.int32)
>>> verts[0] = 0
>>> verts[1] = 1
>>> verts[2] = 2
>>> sverts = cudf.Series(verts)
>>> Sg = cugraph.subgraph(G, sverts)
"""
null_check(vertices)
result_graph = DiGraph()
subgraph_extraction_wrapper.subgraph(G, vertices, result_graph)
return result_graph
def ktruss_subgraph(G, k, use_weights=True):
"""
Returns the subgraph of the k-truss of a graph for a specific k.
The k-truss of a graph is subgraph where each edge is part of at least
(k−2) triangles. k-trusses are used for finding tighlty knit groups of
vertices in a graph. A k-truss is a relaxation of a k-clique in the graph
and was define in [1]. Finding cliques is computationally demanding and
finding the maximal k-clique is known to be NP-Hard.
In contrast, finding a k-truss is computationally tractable as its
key building block, namely triangle counting counting, can be executed
in polnymomial time.Typically, it takes many iterations of triangle
counting to find the k-truss of a graph. Yet these iterations operate
on a weakly monotonically shrinking graph.
Therefore, finding the k-truss of a graph can be done in a fairly
reasonable amount of time. The solution in cuGraph is based on a
GPU algorithm first shown in [2] and uses the triangle counting algorithm
from [3].
[1] Cohen, J.,
"Trusses: Cohesive subgraphs for social network analysis"
National security agency technical report, 2008
[2] O. Green, J. Fox, E. Kim, F. Busato, et al.
“Quickly Finding a Truss in a Haystack”
IEEE High Performance Extreme Computing Conference (HPEC), 2017
https://doi.org/10.1109/HPEC.2017.8091038
[3] O. Green, P. Yalamanchili, L.M. Munguia,
“Fast Triangle Counting on GPU”
Irregular Applications: Architectures and Algorithms (IA3), 2014
Parameters
----------
G : cuGraph.Graph
cuGraph graph descriptor with connectivity information. k-Trusses are
defined for only undirected graphs as they are defined for
undirected triangle in a graph.
k : int
The desired k to be used for extracting the k-truss subgraph.
use_weights : Bool
whether the output should contain the edge weights if G has them
Returns
-------
G_truss : cuGraph.Graph
A cugraph graph descriptor with the k-truss subgraph for the given k.
Examples
--------
>>> M = cudf.read_csv('datasets/karate.csv', delimiter=' ',
>>> dtype=['int32', 'int32', 'float32'], header=None)
>>> G = cugraph.Graph()
>>> G.from_cudf_edge_list(M, source='0', destination='1')
>>> k_subgraph = cugraph.ktruss_subgraph(G, 3)
"""
KTrussSubgraph = DiGraph()
ktruss_subgraph_wrapper.ktruss_subgraph(G, k, use_weights,
KTrussSubgraph)
return KTrussSubgraph
def from_pandas_edgelist(df,
source="source",
destination="destination",
edge_attr=None,
create_using=Graph,
renumber=True):
"""
Initialize a graph from the edge list. It is an error to call this
method on an initialized Graph object. Source argument is source
column name and destination argument is destination column name.
By default, renumbering is enabled to map the source and destination
vertices into an index in the range [0, V) where V is the number
of vertices. If the input vertices are a single column of integers
in the range [0, V), renumbering can be disabled and the original
external vertex ids will be used.
If weights are present, edge_attr argument is the weights column name.
Parameters
----------
input_df : pandas.DataFrame
A DataFrame that contains edge information
source : str or array-like
source column name or array of column names
destination : str or array-like
destination column name or array of column names
edge_attr : str or None
the weights column name. Default is None
renumber : bool
Indicate whether or not to renumber the source and destination
vertex IDs. Default is True.
create_using: cugraph.DiGraph or cugraph.Graph
Indicate whether to create a directed or undirected graph
Returns
-------
G : cugraph.DiGraph or cugraph.Graph
graph containing edges from the pandas edgelist
Examples
--------
>>> df = pandas.read_csv('datasets/karate.csv', delimiter=' ',
>>> dtype=['int32', 'int32', 'float32'], header=None)
>>> G = cugraph.Graph()
>>> G.from_pandas_edgelist(df, source='0', destination='1',
edge_attr='2', renumber=False)
"""
if create_using is Graph:
G = Graph()
elif create_using is DiGraph:
G = DiGraph()
else:
raise Exception("create_using supports Graph and DiGraph")
G.from_pandas_edgelist(df,
source=source,
destination=destination,
edge_attr=edge_attr,
renumber=renumber)
return G