def exp_10():
net = MinTTTLagrangianCTMProblem.load("/Users/jdr/Desktop/out.json")
net.cache_props()
print len(net.sources)
print len(net.sinks)
print len(net.all_routes())
print len(net.get_links())
# for route in net.all_routes():
# print net.max_flow(route), net.ff_travel_time(route)
import networkx
print networkx.is_weakly_connected(net)
with open('/Users/jdr/Desktop/flowdata.csv','r') as fn:
flows = {}
for row in fn:
splits = row[:-1].split(';')
print splits
name = splits[2]
flow = float(splits[1])
density = float(splits[0])
flows[name] = {
'flow': flow,
'density': density
}
def get_flows(link):
try:
return flows[link.name]['flow']
except:
return 0.0
for junction in net.junctions:
lsum = sum(get_flows(link) for link in junction.in_links)
rsum = sum(get_flows(link) for link in junction.out_links)
print lsum, rsum
for link in net.get_links():
print bool(link.fd.q_max < get_flows(link)), link.fd.q_max, get_flows(link)
def subgraphs_product(G1, G2, length):
assert length <= len(G1.nodes())
assert length <= len(G2.nodes())
a = it.combinations(G1.nodes(), length)
b = it.combinations(G2.nodes(), length)
gen = it.product(a, b)
for pair in gen:
sub1 = G1.subgraph(pair[0])
sub2 = G2.subgraph(pair[1])
if nx.is_weakly_connected(sub1) and nx.is_weakly_connected(sub2):
yield (sub1, sub2)
def connected(self):
"""
Test if the graph is connected.
Return True if connected, False otherwise
"""
return nx.is_weakly_connected(self.G)
def gen_network(graph,machines,basedata):
""" Generates an LLD network from a graph
distributing participants in a list of machines
"""
network = ET.Element('network')
#network.set('type',graphtype)
network.set('participants',str(graph.number_of_nodes()))
network.set('edges',str(graph.size()))
network.set('density',str(NX.density(graph)))
network.set('connected',str(NX.is_weakly_connected(graph)))
network.set('stronglyconnected',str(NX.is_strongly_connected(graph)))
for node in graph.nodes_iter():
nodelement = ET.SubElement(network,'participant')
nodelement.set('id','participant'+str(node))
hostelem = ET.SubElement(nodelement,'host')
#hostelem.text = 'node'+str(int(node) % len(machines))
hostelem.text = machines[int(node) % len(machines)]
portelem = ET.SubElement(nodelement,'port')
portelem.text = str(20500+int(node))
baseelem = ET.SubElement(nodelement,'basedata')
baseelem.text = basedata
nodelement.append(gen_dynamic())
for source in gen_sources(graph,node):
nodelement.append(source)
return network
def draw_graph(nodes, edges, graphs_dir, default_lang='all'):
lang_graph = nx.MultiDiGraph()
lang_graph.add_nodes_from(nodes)
for edge in edges:
if edges[edge] == 0:
lang_graph.add_edge(edge[0], edge[1])
else:
lang_graph.add_edge(edge[0], edge[1], weight=float(edges[edge]), label=str(edges[edge]))
# print graph info in stdout
# degree centrality
print('-----------------\n\n')
print(default_lang)
print(nx.info(lang_graph))
try:
# When ties are associated to some positive aspects such as friendship or collaboration,
# indegree is often interpreted as a form of popularity, and outdegree as gregariousness.
DC = nx.degree_centrality(lang_graph)
max_dc = max(DC.values())
max_dc_list = [item for item in DC.items() if item[1] == max_dc]
except ZeroDivisionError:
max_dc_list = []
# https://ru.wikipedia.org/wiki/%D0%9A%D0%BE%D0%BC%D0%BF%D0%BB%D0%B5%D0%BA%D1%81%D0%BD%D1%8B%D0%B5_%D1%81%D0%B5%D1%82%D0%B8
print('maxdc', str(max_dc_list), sep=': ')
# assortativity coef
AC = nx.degree_assortativity_coefficient(lang_graph)
print('AC', str(AC), sep=': ')
# connectivity
print("Слабо-связный граф: ", nx.is_weakly_connected(lang_graph))
print("количество слабосвязанных компонент: ", nx.number_weakly_connected_components(lang_graph))
print("Сильно-связный граф: ", nx.is_strongly_connected(lang_graph))
print("количество сильносвязанных компонент: ", nx.number_strongly_connected_components(lang_graph))
print("рекурсивные? компоненты: ", nx.number_attracting_components(lang_graph))
print("число вершинной связности: ", nx.node_connectivity(lang_graph))
print("число рёберной связности: ", nx.edge_connectivity(lang_graph))
# other info
print("average degree connectivity: ", nx.average_degree_connectivity(lang_graph))
print("average neighbor degree: ", sorted(nx.average_neighbor_degree(lang_graph).items(),
key=itemgetter(1), reverse=True))
# best for small graphs, and our graphs are pretty small
print("pagerank: ", sorted(nx.pagerank_numpy(lang_graph).items(), key=itemgetter(1), reverse=True))
plt.figure(figsize=(16.0, 9.0), dpi=80)
plt.axis('off')
pos = graphviz_layout(lang_graph)
nx.draw_networkx_edges(lang_graph, pos, alpha=0.5, arrows=True)
nx.draw_networkx(lang_graph, pos, node_size=1000, font_size=12, with_labels=True, node_color='green')
nx.draw_networkx_edge_labels(lang_graph, pos, edges)
# saving file to draw it with dot-graphviz
# changing overall graph view, default is top-bottom
lang_graph.graph['graph'] = {'rankdir': 'LR'}
# marking with blue nodes with maximum degree centrality
for max_dc_node in max_dc_list:
lang_graph.node[max_dc_node[0]]['fontcolor'] = 'blue'
write_dot(lang_graph, os.path.join(graphs_dir, default_lang + '_links.dot'))
# plt.show()
plt.savefig(os.path.join(graphs_dir, 'python_' + default_lang + '_graph.png'), dpi=100)
plt.close()
def evaluate(graph):
"""evaluate(Graph) -> None
:class:`Graph` -> IO ()
Starting from the root node, evaluate the branches.
The graph nodes are updated in-place.
Example:
>>> @delayed()
... def foo(a):
... return a
>>> node = foo(42) & foo(24)
>>> print evaluate(node.graph)
None
>>> for _, data in node.graph.nodes(data=True):
... n = data['node']
... print n.name, n.result.result()
& None
foo 42
foo 24
"""
assert nx.is_weakly_connected(graph)
node = find_root_node(graph)
node.eval()
def average_shortest_path_length(G, weight=None):
r"""Return the average shortest path length.
The average shortest path length is
.. math::
a =\sum_{s,t \in V} \frac{d(s, t)}{n(n-1)}
where `V` is the set of nodes in `G`,
`d(s, t)` is the shortest path from `s` to `t`,
and `n` is the number of nodes in `G`.
Parameters
----------
G : NetworkX graph
weight : None or string, optional (default = None)
If None, every edge has weight/distance/cost 1.
If a string, use this edge attribute as the edge weight.
Any edge attribute not present defaults to 1.
Raises
------
NetworkXError:
if the graph is not connected.
Examples
--------
>>> G=nx.path_graph(5)
>>> print(nx.average_shortest_path_length(G))
2.0
For disconnected graphs you can compute the average shortest path
length for each component:
>>> G=nx.Graph([(1,2),(3,4)])
>>> for g in nx.connected_component_subgraphs(G):
... print(nx.average_shortest_path_length(g))
1.0
1.0
"""
if G.is_directed():
if not nx.is_weakly_connected(G):
raise nx.NetworkXError("Graph is not connected.")
else:
if not nx.is_connected(G):
raise nx.NetworkXError("Graph is not connected.")
avg=0.0
if weight is None:
for node in G:
path_length=nx.single_source_shortest_path_length(G, node)
avg += sum(path_length.values())
else:
for node in G:
path_length=nx.single_source_dijkstra_path_length(G, node, weight=weight)
avg += sum(path_length.values())
n=len(G)
return avg/(n*(n-1))
def is_connected(self):
"""
Return True if the Xmrs represents a connected graph.
Subgraphs can be connected through things like arguments,
QEQs, and label equalities.
"""
try:
return nx.is_weakly_connected(self._graph)
except nx.exception.NetworkXPointlessConcept:
raise XmrsError("Connectivity is undefined for an empty Xmrs.")
def random_connected_graph(numNodes, numEdges):
'''Generates a weakly connected random graph with numNodes nodes
and numEdges edges
'''
tries = 0
while tries < 100:
tries += 1
random_graph = nx.gnm_random_graph(numNodes,numEdges,directed = True)
if nx.is_weakly_connected(random_graph):
return random_graph
return None
def _infer_all_ratios(self, ratios):
def compute_path_attribs(path, G, attribs):
ret = {attr: 1.0 for attr in attribs}
if len(path) > 1:
for i in range(len(path) - 1):
for attr in attribs:
ret[attr] *= G[path[i]][path[i + 1]][attr]
return ret
G = nx.convert_matrix.from_pandas_edgelist(
ratios,
'v1',
'v2',
edge_attr=['weight', "ratio", "ratio_hi", "ratio_lo", 'error'],
create_using=nx.DiGraph)
assert len(G.edges()) % 2 == 0
# strongly?
if not nx.is_strongly_connected(G) or not nx.is_weakly_connected(
G) or nx.number_connected_components(nx.Graph(G)) > 1:
for comp in nx.connected_components(nx.Graph(G)):
self._print_and_log(
f"Component with length {len(comp)}: {str(comp)}")
self._error_flag = True
self._print_and_log(
f"Num. connected components: {nx.number_strongly_connected_components(G)}. "
f"Directed graph is not strongly connected!")
warnings.warn("Directed graph is not connected!")
# ratios.to_csv("ratios_test.tsv", sep = '\t')
paths = list(nx.all_pairs_dijkstra_path(G))
self.paths = paths
node_names = [el[0] for el in paths]
W = pd.DataFrame(columns=node_names, index=node_names, dtype=float)
W_lo = pd.DataFrame(columns=node_names, index=node_names, dtype=float)
W_hi = pd.DataFrame(columns=node_names, index=node_names, dtype=float)
self._print_and_log("Finding paths...")
for p_obj in tqdm(paths):
for p in p_obj[1].values():
path_attrib_dict = compute_path_attribs(
p, G, ['weight', "ratio", "ratio_hi", "ratio_lo", 'error'])
v1 = p[0]
v2 = p[-1]
W.loc[v1][v2] = path_attrib_dict['ratio']
W_lo.loc[v1][v2] = path_attrib_dict['ratio_lo']
W_hi.loc[v1][v2] = path_attrib_dict['ratio_hi']
self._print_and_log("Paths done!")
return W, W_lo, W_hi
def answer_three():
file = 'email_network.txt'
G = nx.read_edgelist(file,
delimiter='\t',
data=[('time', int)],
create_using=nx.DiGraph())
part1 = nx.is_strongly_connected(G)
part2 = nx.is_weakly_connected(G)
return (part1, part2)
def output_conectivity_info (graph, path):
"""Output connectivity information about the graph.
graph : (networkx.Graph)
path: (String) contains the path to the output file
"""
with open(path, 'w') as out:
out.write('***Conectivity***\n')
out.write('Is weakly connected: %s\n' % nx.is_weakly_connected(graph))
out.write('Number of weakly connected components: %d\n' % nx.number_weakly_connected_components(graph))
out.write('Is strongly connected: %s\n' % nx.is_strongly_connected(graph))
out.write('Number of strongly connected components: %d' % nx.number_strongly_connected_components(graph))
def _get_subgraphs(self, graph, name, size=3):
subgraphs = set()
# print "\nSubgraphs START: " + name
target = nx.complete_graph(size)
for sub_nodes in itertools.combinations(graph.nodes(),len(target.nodes())):
subg = graph.subgraph(sub_nodes)
if nx.is_weakly_connected(subg):
# print subg.edges()
subgraphs.add(subg)
# print "Subgraphs END \n"
return subgraphs
def _get_subgraphs(self, graph, name, size=3):
subgraphs = set()
# print "\nSubgraphs START: " + name
target = nx.complete_graph(size)
for sub_nodes in itertools.combinations(graph.nodes(),
len(target.nodes())):
subg = graph.subgraph(sub_nodes)
if nx.is_weakly_connected(subg):
# print subg.edges()
subgraphs.add(subg)
# print "Subgraphs END \n"
return subgraphs
def set_domain(clz, dag):
""" Sets the domain. Should only be called once per class instantiation. """
logging.info("Setting domain for poset %s" % clz.__name__)
if nx.number_of_nodes(dag) == 0:
raise CellConstructionFailure("Empty DAG structure.")
if not nx.is_directed_acyclic_graph(dag):
raise CellConstructionFailure("Must be directed and acyclic")
if not nx.is_weakly_connected(dag):
raise CellConstructionFailure("Must be connected")
clz.domain_map[clz] = dag
def rooted_core_interface_pairs(self, root, thickness=None, for_base=False,
hash_bitmask=None,
radius_list=[],
thickness_list=None,
node_filter=lambda x, y: True):
"""
Parameters
----------
root:
thickness:
args:
Returns
-------
"""
ciplist = super(self.__class__, self).rooted_core_interface_pairs(root, thickness, for_base=for_base,
hash_bitmask=hash_bitmask,
radius_list=radius_list,
thickness_list=thickness_list,
node_filter=node_filter)
# numbering shards if cip graphs not connected
for cip in ciplist:
if not nx.is_weakly_connected(cip.graph):
comps = [list(node_list) for node_list in nx.weakly_connected_components(cip.graph)]
comps.sort()
for i, nodes in enumerate(comps):
for node in nodes:
cip.graph.node[node]['shard'] = i
'''
solve problem of single-ede-nodes in the core
this may replace the need for fix_structure thing
this is a little hard.. may fix later
it isnt hard if i write this code in merge_core in ubergraphlearn
for cip in ciplist:
for n,d in cip.graph.nodes(data=True):
if 'edge' in d and 'interface' not in d:
if 'interface' in cip.graph.node[ cip.graph.successors(n)[0]]:
#problem found
'''
return ciplist
def check_weakly_connected(series):
series = series[1]
tmp_df = series.reset_index()
tmp_df['sign'] = series.values
delete_edges = tmp_df[tmp_df['sign'] == 0]
dg = nx.from_pandas_dataframe(tmp_df,
source='source',
target='target',
edge_attr=['sign'],
create_using=nx.DiGraph())
dg.remove_edges_from(delete_edges.edge.values.tolist())
return nx.is_weakly_connected(dg)
def check_connection(Graph):
if nx.is_directed(Graph):
try:
is_connected = nx.is_weakly_connected(Graph)
except (ValueError, RuntimeError, TypeError, NameError):
pass
else:
try:
is_connected = nx.is_connected(Graph)
except (ValueError, RuntimeError, TypeError, NameError):
pass
return is_connected
def random_generator(n: int, k: int, alpha: int, graph_version: int):
"""
Generates a random connected graph with all the node attributes set to 3 and the edge weights to 1
:param graph_version: file version
:param alpha:
:param n: number of nodes
:param k:
:return:
"""
# Generate an almost complete graph
graph = nx.DiGraph(
nx.MultiDiGraph.to_directed(
nx.random_k_out_graph(n, k, self_loops=False, alpha=alpha)))
# # Delete incoming arcs from 0 -> starting node
# graph.remove_edges_from([(v1, v2) for (v1, v2) in graph.in_edges if v2 is 0])
# Connect the first and the last node
graph.add_edges_from([(0, max(graph.nodes))])
print(len(graph.edges))
for node in graph.nodes:
incoming = [(v1, v2) for (v1, v2) in graph.in_edges if v2 == node]
deleted_nodes = 0
# Randomly decide if an edge has to be kept or discarded
for edge in incoming:
keep = np.average(rnd.binomial(1, 0.55, 5))
# Delete only if the nodes has more than one incoming and outcoming edge
if keep >= 0.4 and deleted_nodes < len(incoming) - 1 and len(
graph.edges(edge[0])) > 1:
graph.remove_edge(edge[0], edge[1])
deleted_nodes = deleted_nodes + 1
# Delete node cycles in order to save the graph as strict. Otherwise the graph is by default a multi-weight graph
node_cycles = [(u, v) for (u, v) in graph.edges() if u in graph[v]]
graph.remove_edges_from(node_cycles)
# Connect every arc to the first one
graph.add_edges_from([(node, 0) for node in graph.nodes if node is not 0])
# Set the attributes
nx.set_node_attributes(graph, 3, 'component_delay')
nx.set_edge_attributes(graph, 1, 'wire_delay')
# Save it only if it is connected
if nx.is_weakly_connected(graph):
nx.nx_agraph.write_dot(
graph,
os.getcwd() + '/../rand-graphs/clean/{}/rand-{}-{}.dot'.format(
n, n, graph_version))
return True
else:
return False
def answer_three():
df = pd.read_csv("email_network.txt",
delimiter="\t",
header=0,
dtype={
"#Sender": "str",
"Recipient": "str"
})
directed = nx.from_pandas_dataframe(df,
"#Sender",
"Recipient",
create_using=nx.MultiDiGraph())
return (len(sorted(nx.strongly_connected_components(directed))) == 1
), nx.is_weakly_connected(directed)
def is_semiconnected(G):
"""Return True if the graph is semiconnected, False otherwise.
A graph is semiconnected if, and only if, for any pair of nodes, either one
is reachable from the other, or they are mutually reachable.
Parameters
----------
G : NetworkX graph
A directed graph.
Returns
-------
semiconnected : bool
True if the graph is semiconnected, False otherwise.
Raises
------
NetworkXNotImplemented :
If the input graph is undirected.
NetworkXPointlessConcept :
If the graph is empty.
Examples
--------
>>> G=nx.path_graph(4,create_using=nx.DiGraph())
>>> print(nx.is_semiconnected(G))
True
>>> G=nx.DiGraph([(1, 2), (3, 2)])
>>> print(nx.is_semiconnected(G))
False
See Also
--------
is_strongly_connected
is_weakly_connected
is_connected
is_biconnected
"""
if len(G) == 0:
raise nx.NetworkXPointlessConcept(
'Connectivity is undefined for the null graph.')
if not nx.is_weakly_connected(G):
return False
G = nx.condensation(G)
path = nx.topological_sort(G)
return all(G.has_edge(u, v) for u, v in pairwise(path))
def output_conectivity_info(graph, path):
"""Output connectivity information about the graph.
graph : (networkx.Graph)
path: (String) contains the path to the output file
"""
with open(path, 'w') as out:
out.write('***Conectivity***\n')
out.write('Is weakly connected: %s\n' % nx.is_weakly_connected(graph))
out.write('Number of weakly connected components: %d\n' %
nx.number_weakly_connected_components(graph))
out.write('Is strongly connected: %s\n' %
nx.is_strongly_connected(graph))
out.write('Number of strongly connected components: %d' %
nx.number_strongly_connected_components(graph))
def get_subgraphs(graph):
"""
extract subgraphs from a given annot
"""
nodes_powerset = get_nodes_combinations(graph)
#print("Doing")
#draw_graph(graph)
subgraphs = []
for nodes in nodes_powerset:
subg = graph.subgraph(nodes)
nodes = subg.nodes(data=True)
if nx.is_weakly_connected(subg):
subgraphs.append(subg)
return subgraphs
def is_semiconnected(G):
"""Returns True if the graph is semiconnected, False otherwise.
A graph is semiconnected if, and only if, for any pair of nodes, either one
is reachable from the other, or they are mutually reachable.
Parameters
----------
G : NetworkX graph
A directed graph.
Returns
-------
semiconnected : bool
True if the graph is semiconnected, False otherwise.
Raises
------
NetworkXNotImplemented :
If the input graph is undirected.
NetworkXPointlessConcept :
If the graph is empty.
Examples
--------
>>> G=nx.path_graph(4,create_using=nx.DiGraph())
>>> print(nx.is_semiconnected(G))
True
>>> G=nx.DiGraph([(1, 2), (3, 2)])
>>> print(nx.is_semiconnected(G))
False
See Also
--------
is_strongly_connected
is_weakly_connected
is_connected
is_biconnected
"""
if len(G) == 0:
raise nx.NetworkXPointlessConcept(
'Connectivity is undefined for the null graph.')
if not nx.is_weakly_connected(G):
return False
G = nx.condensation(G)
path = nx.topological_sort(G)
return all(G.has_edge(u, v) for u, v in pairwise(path))
def answer_three():
# Your Code Here
'''
nodes = answer_one().nodes()
edges = answer_one().edges()
starts = set(sorted([i[0] for i in edges]))
ends = set(sorted([i[1] for i in edges]))
print(set(sorted(nodes)).issubset(starts))
print(set(sorted(nodes)).issubset(starts.union(ends)))
print(nx.is_strongly_connected(answer_one()))
print(nx.is_weakly_connected(answer_one()))
'''
return (nx.is_strongly_connected(answer_one()),nx.is_weakly_connected(answer_one()))# Your Answer Here
def purify_graph(self):
coverages = get_coverage(self.graph)
first_edge = None
for (edge, e_cov) in sorted(coverages.items(),
key=lambda x: (-x[1], x[0])):
if self.graph.out_degree(edge[0]) == 1 \
and self.graph.in_degree(edge[1]) == 1:
first_edge = edge
break
first_edge_properties = self.graph.edges[first_edge]
self.graph.remove_edge(*first_edge)
while True:
coverages = get_coverage(self.graph)
edge2remove = None
for (edge, e_cov) in sorted(coverages.items(),
key=lambda x: (x[1], x[0])):
gr = self.graph.copy()
gr.remove_edge(*edge)
if nx.is_weakly_connected(gr):
edge2remove = edge
break
if edge2remove is not None:
self.graph.remove_edge(*edge2remove)
assert nx.is_weakly_connected(self.graph)
self.graph.remove_nodes_from(list(nx.isolates(self.graph)))
assert nx.is_weakly_connected(self.graph)
self.collapse_nonbranching_paths(respect_color=False)
assert nx.is_weakly_connected(self.graph)
else:
break
self.graph.add_edge(*first_edge, **first_edge_properties)
self.remove_tips()
self.collapse_nonbranching_paths(respect_color=False)
def get_largest_component(G, strongly=False):
"""
Return the largest weakly or strongly connected component from a directed
graph.
Parameters
----------
G : networkx multidigraph
strongly : bool
if True, return the largest strongly instead of weakly connected
component
Returns
-------
networkx multidigraph
"""
start_time = time.time()
original_len = len(list(G.nodes()))
if strongly:
# if the graph is not connected and caller did not request retain_all,
# retain only the largest strongly connected component
if not nx.is_strongly_connected(G):
G = max(nx.strongly_connected_component_subgraphs(G), key=len)
msg = (
'Graph was not connected, retained only the largest strongly '
'connected component ({:,} of {:,} total nodes) in {:.2f} seconds'
)
log(
msg.format(len(list(G.nodes())), original_len,
time.time() - start_time))
else:
# if the graph is not connected and caller did not request retain_all,
# retain only the largest weakly connected component
if not nx.is_weakly_connected(G):
subgraphs = [
G.subgraph(c).copy() for c in nx.weakly_connected_components(G)
]
G = max(subgraphs, key=len)
msg = (
'Graph was not connected, retained only the largest weakly '
'connected component ({:,} of {:,} total nodes) in {:.2f} seconds'
)
log(
msg.format(len(list(G.nodes())), original_len,
time.time() - start_time))
return G
def get_largest_component(G, strongly=False):
"""
Get subgraph of MultiDiGraph's largest weakly/strongly connected component.
Parameters
----------
G : networkx.MultiDiGraph
input graph
strongly : bool
if True, return the largest strongly instead of weakly connected
component
Returns
-------
G : networkx.MultiDiGraph
the largest connected component subgraph from the original graph
"""
original_len = len(list(G.nodes()))
if strongly:
# if the graph is not connected retain only the largest strongly connected component
if not nx.is_strongly_connected(G):
# get all the strongly connected components in graph then identify the largest
sccs = nx.strongly_connected_components(G)
largest_scc = max(sccs, key=len)
G = induce_subgraph(G, largest_scc)
msg = (
f"Graph was not connected, retained only the largest strongly "
f"connected component ({len(G)} of {original_len} total nodes)"
)
utils.log(msg)
else:
# if the graph is not connected retain only the largest weakly connected component
if not nx.is_weakly_connected(G):
# get all the weakly connected components in graph then identify the largest
wccs = nx.weakly_connected_components(G)
largest_wcc = max(wccs, key=len)
G = induce_subgraph(G, largest_wcc)
msg = (
f"Graph was not connected, retained only the largest weakly "
f"connected component ({len(G)} of {original_len} total nodes)"
)
utils.log(msg)
return G
def is_fully_connected(graph):
r"""
Checks whether the input graph is fully connected in the undirected case
or weakly connected in the directed case.
Connected means one can get from any vertex :math:`u` to vertex :math:`v` by traversing
the graph. For a directed graph, weakly connected means that the graph
is connected after it is converted to an unweighted graph (ignore the
direction of each edge)
Parameters
----------
graph: nx.Graph, nx.DiGraph, nx.MultiDiGraph, nx.MultiGraph,
scipy.sparse.csr_matrix, np.ndarray
Input graph in any of the above specified formats. If np.ndarray,
interpreted as an :math:`n \times n` adjacency matrix
Returns
-------
boolean: True if the entire input graph is connected
References
----------
http://mathworld.wolfram.com/ConnectedGraph.html
http://mathworld.wolfram.com/WeaklyConnectedDigraph.html
Examples
--------
>>> a = np.array([
... [0, 1, 0],
... [1, 0, 0],
... [0, 0, 0]])
>>> is_fully_connected(a)
False
"""
if isinstance(graph, (np.ndarray, csr_matrix)):
directed = not is_symmetric(graph)
n_components = connected_components(
csgraph=graph, directed=directed, connection="weak", return_labels=False
)
return n_components == 1
else:
if type(graph) in [nx.Graph, nx.MultiGraph]:
return nx.is_connected(graph)
elif type(graph) in [nx.DiGraph, nx.MultiDiGraph]:
return nx.is_weakly_connected(graph)
def MSCG(self, G, E_neg):
Q = sorted(E_neg, key=operator.itemgetter(1), reverse=True)
num_weakly_connected = nx.number_weakly_connected_components(G)
while len(Q) > 0 and not nx.is_weakly_connected(G):
try:
candidate_edge, candidate_score = Q.pop(0)
except IndexError:
break
head, tail, label = candidate_edge
if tail in G[head] or head in G[tail]:
continue
G.add_edge(*candidate_edge)
new_num_weakly_connected = nx.number_weakly_connected_components(G)
if new_num_weakly_connected < num_weakly_connected:
num_weakly_connected = new_num_weakly_connected
else:
G.remove_edge(*candidate_edge[:2])
assert nx.is_weakly_connected(G)
def answer_three():
# Your Code Here
# initialise the graph
G = answer_one()
# check if the graph is strongly connected to answer part 1
strongly_connected_status = nx.is_strongly_connected(G)
# check if the graph is weakly connected to answer part 2
weakly_connected_status = nx.is_weakly_connected(G)
return (strongly_connected_status, weakly_connected_status
) # Your Answer Here
def is_connected(graph, kwargs={}):
'''
Checks if a network has a sequence of edges from each node to every other node regardless of edge direction.
This is weak connectivity in a directed graph.
:param graph: A dsgrn_net_gen.graphtranslation object
:param kwargs: empty dictionary, here for API compliance
:return: (True, "") or (False, error message), True if satisfied
'''
G = nx.DiGraph()
G.add_edges_from(graph.edges())
G.add_nodes_from(graph.vertices())
if G and nx.is_weakly_connected(G):
return True, ""
else:
return False, "Not connected"
def IsRootedTree(digraph):
if len(digraph.edges) != len(
digraph.nodes) - 1 or not nx.is_weakly_connected(digraph):
return False
rootFound = False
root = False
for node in digraph:
if digraph.in_degree(node) == 0:
if rootFound:
return False
rootFound = True
root = node
if digraph.in_degree(node) > 1:
return False
return root
def generate_triads_1(network): """ Generate triads by making all node combinations, filtering < 2 edges. Not suitable for large graphs. """ nodes = network.nodes() node_combos = list(itertools.combinations(nodes, 3)) triads = [] for combo in node_combos: sub_graph = network.subgraph(combo) if nx.is_weakly_connected(sub_graph): triads.append(sub_graph) return triads
def satisfies(self, graph):
"""
This constraint is only satisfied if the provided graph as is weakly
connected.
:param graph: a graph to test
:type graph: nx.DiGraph
:returns: ``True`` if the digraph as the desired number of external
nodes
"""
if super().satisfies(graph):
try:
return nx.is_weakly_connected(graph)
except nx.exception.NetworkXException as err:
raise ConstraintError() from err
def get_largest_component(G, strongly=False, verbose=False):
"""
https://github.com/gboeing/osmnx/blob/master/osmnx/utils.py
Return a subgraph of the largest weakly or strongly connected component
from a directed graph.
Parameters
----------
G : networkx multidigraph
strongly : bool
if True, return the largest strongly instead of weakly connected
component
Returns
-------
G : networkx multidigraph
the largest connected component subgraph from the original graph
"""
start_time = time.time()
original_len = len(list(G.nodes()))
if strongly:
# if the graph is not connected retain only the largest strongly connected component
if not nx.is_strongly_connected(G):
# get all the strongly connected components in graph then identify the largest
sccs = nx.strongly_connected_components(G)
largest_scc = max(sccs, key=len)
G = induce_subgraph(G, largest_scc)
msg = ('Graph was not connected, retained only the largest strongly '
'connected component ({:,} of {:,} total nodes) in {:.2f} seconds')
if verbose:
print(msg.format(len(list(G.nodes())), original_len, time.time()-start_time))
else:
# if the graph is not connected retain only the largest weakly connected component
if not nx.is_weakly_connected(G):
# get all the weakly connected components in graph then identify the largest
wccs = nx.weakly_connected_components(G)
largest_wcc = max(wccs, key=len)
G = induce_subgraph(G, largest_wcc)
msg = ('Graph was not connected, retained only the largest weakly '
'connected component ({:,} of {:,} total nodes) in {:.2f} seconds')
if verbose:
print(msg.format(len(list(G.nodes())), original_len, time.time()-start_time))
return G
def random_dag(n, p=0.5, weakly_connected=True):
"""Return a random directed acyclic graph (DAG) with a n nodes and
p(edges)."""
adj_matrix = numpy.tril(numpy.random.binomial(1, p, size=(n, n)), -1)
G = networkx.from_numpy_array(adj_matrix, create_using=PrecedenceGraph())
if weakly_connected and not networkx.is_weakly_connected(G):
for g in networkx.weakly_connected_component_subgraphs(G.copy()):
nodes = list(networkx.topological_sort(g))
G.add_edge('start', nodes[0])
G.add_edge(nodes[-1], 'stop')
assert (networkx.is_directed_acyclic_graph(G))
return G
def compute_measures(self):
"""obtain measures"""
#degrees = self.network.degree()
degree_distr = dict(self.network.degree()).values()
in_degree_distr = dict(self.network.in_degree()).values()
out_degree_distr = dict(self.network.out_degree()).values()
is_connected = nx.is_weakly_connected(self.network)
#is_connected = nx.is_strongly_connected(self.network) # must always be False
try:
node_centralities = nx.eigenvector_centrality(self.network)
except:
node_centralities = nx.betweenness_centrality(self.network)
# TODO: and more, choose more meaningful ones...
print("Graph is connected: ", is_connected, "\nIn degrees ", in_degree_distr, "\nOut degrees", out_degree_distr, \
"\nCentralities", node_centralities)
def filter_molecules(molecules, connectivity=True, isomorphism=True):
"""
Filter out molecules that are not connected and molecules with the same
isomorphism (keep the lowest energy).
Args:
molecules (list of MoleculeWrapper): molecules
connectivity (bool): whether to filter on connectivity
isomorphism (bool): if `True`, filter on `charge`, `spin`, and `isomorphism`.
The one with the lowest free energy will remain.
Returns:
A list of MoleculeWrapper objects.
"""
n_unconnected_mol = 0
n_not_unique_mol = 0
filtered = []
for i, m in enumerate(molecules):
# check on connectivity
if connectivity and not nx.is_weakly_connected(m.graph):
n_unconnected_mol += 1
continue
# check for isomorphism
if isomorphism:
idx = -1
for i_p_m, p_m in enumerate(filtered):
if (m.charge == p_m.charge
and m.spin_multiplicity == p_m.spin_multiplicity
and m.mol_graph.isomorphic_to(p_m.mol_graph)):
n_not_unique_mol += 1
idx = i_p_m
break
if idx >= 0:
if m.free_energy < filtered[idx].free_energy:
filtered[idx] = m
else:
filtered.append(m)
logger.info(
"Num molecules: {}; unconnected: {}; isomorphic: {}; remaining: {}"
.format(len(molecules), n_unconnected_mol, n_not_unique_mol,
len(filtered)))
return filtered
def get_largest_component(G, strongly=False):
"""
Return a subgraph of the largest weakly or strongly connected component
from a directed graph.
Parameters
----------
G : networkx multidigraph
strongly : bool
if True, return the largest strongly instead of weakly connected
component
Returns
-------
G : networkx multidigraph
the largest connected component subgraph from the original graph
"""
start_time = time.time()
original_len = len(list(G.nodes()))
if strongly:
# if the graph is not connected retain only the largest strongly connected component
if not nx.is_strongly_connected(G):
# get all the strongly connected components in graph then identify the largest
sccs = nx.strongly_connected_components(G)
largest_scc = max(sccs, key=len)
G = induce_subgraph(G, largest_scc)
msg = ('Graph was not connected, retained only the largest strongly '
'connected component ({:,} of {:,} total nodes) in {:.2f} seconds')
log(msg.format(len(list(G.nodes())), original_len, time.time()-start_time))
else:
# if the graph is not connected retain only the largest weakly connected component
if not nx.is_weakly_connected(G):
# get all the weakly connected components in graph then identify the largest
wccs = nx.weakly_connected_components(G)
largest_wcc = max(wccs, key=len)
G = induce_subgraph(G, largest_wcc)
msg = ('Graph was not connected, retained only the largest weakly '
'connected component ({:,} of {:,} total nodes) in {:.2f} seconds')
log(msg.format(len(list(G.nodes())), original_len, time.time()-start_time))
return G
def all_kgraphs_naive(V, K):
graphlist = []
kp = K + 1
# This generates the set of all nonparallel kgraphs by generating the set of all numbers from 0 to
# (K+1)^(V^2)
#for each edge, it either
for i in range(((kp)**(V * V))):
# print "---"
# print "i = {0}".format(i)
# The algorithm used is actually the same to convert an integer into a (V^2) digit base-K number
# pretty cool, huh?
# clones i
j = i
# resets index
index = 0
# digit is the array of digits holding our graph info
digit = [0] * (V * V)
# print "j = {0}".format(j)
while (j != 0):
remainder = j % (kp) # assume K > 1
j = j / (kp) #integer division
digit[index] = remainder
index += 1
G = new_kgraph(V, K)
#for every edge
print digit
for m in range(V):
# print m
for n in range(V):
# print n
#gets the index of the edge
index = (m * V) + n
# if the set digit is zero, do not add the edge
# print "{0} {1}".format(index,digit[index])
if (digit[index] != 0):
#otherwise, add the edge according to stored
G.add_edge(string.ascii_lowercase[m],
string.ascii_lowercase[n],
k=digit[index])
if not nx.is_weakly_connected(G):
continue
if not quick_invalid(G):
continue
graphlist.append(G)
return graphlist
def test_build_worlds(self):
n = 6
G = nx.grid_2d_graph(n, n, create_using=nx.DiGraph())
for n in G.nodes():
G.nodes[n]['coords'] = (n[0], n[1])
G = nx.convert_node_labels_to_integers(G)
superworld = SplitSolver.build_superworld(G, 4)
assert len(superworld) == 4
for n in superworld.nodes(data=True):
assert abs(len(n[1]['nodes']) - 9) <= 3 # might not be equal
for n2 in n[1]['nodes']:
assert G.has_node(n2)
assert nx.is_weakly_connected(G.subgraph(n[1]['nodes']))
assert superworld.number_of_edges() >= 4
# might be greater than 8, because splitting might not be exactly square-based (due to hilbert approximation)
for n in G.nodes(data=True):
assert 'supernode' in n[1]
def feature(node, edge):
G = nx.MultiGraph()
G = G.to_directed()
G.add_nodes_from(node)
G.add_edges_from(edge)
f = np.zeros(10)
f[0] = len(G.nodes)
f[1] = len(G.edges)
f[2] = nx.density(G)
f[3] = nx.degree_pearson_correlation_coefficient(G)
f[4] = nx.algorithms.reciprocity(G)
f[5] = 0 #nx.transitivity(G)
f[6] = nx.is_weakly_connected(G)
f[7] = nx.number_weakly_connected_components(G)
f[8] = nx.is_strongly_connected(G)
f[9] = nx.number_strongly_connected_components(G)
return f
def has_eulerian_path(G):
"""Return True iff `G` has an Eulerian path.
An Eulerian path is a path in a graph which uses each edge of a graph
exactly once.
A directed graph has an Eulerian path iff:
- at most one vertex has out_degree - in_degree = 1,
- at most one vertex has in_degree - out_degree = 1,
- every other vertex has equal in_degree and out_degree,
- and all of its vertices with nonzero degree belong to a
- single connected component of the underlying undirected graph.
An undirected graph has an Eulerian path iff:
- exactly zero or two vertices have odd degree,
- and all of its vertices with nonzero degree belong to a
- single connected component.
Parameters
----------
G : NetworkX Graph
The graph to find an euler path in.
Returns
-------
Bool : True if G has an eulerian path.
See Also
--------
is_eulerian
eulerian_path
"""
if G.is_directed():
ins = G.in_degree
outs = G.out_degree
semibalanced_ins = sum(ins(v) - outs(v) == 1 for v in G)
semibalanced_outs = sum(outs(v) - ins(v) == 1 for v in G)
return (
semibalanced_ins <= 1
and semibalanced_outs <= 1
and sum(G.in_degree(v) != G.out_degree(v) for v in G) <= 2
and nx.is_weakly_connected(G)
)
else:
return sum(d % 2 == 1 for v, d in G.degree()) in (0, 2) and nx.is_connected(G)
def is_semieulerian(G):
"""Returns ``True`` if and only if ``G`` has an Eulerian path.
An Eulerian path is a path that crosses every edge in G
exactly once.
Parameters
----------
G: NetworkX Graph, DiGraph, MultiGraph or MultiDiGraph
A directed or undirected Graph or MultiGraph.
Returns
-------
True, False
See Also
--------
is_eulerian()
Examples
--------
>>> G = nx.DiGraph([(1,2),(2,3)])
>>> nx.is_semieulerian(G)
True
"""
is_directed = G.is_directed()
# Verify that graph is connected, short circuit
if is_directed and not nx.is_weakly_connected(G):
return False
# is undirected
if not is_directed and not nx.is_connected(G):
return False
# Not all vertex have even degree, check if exactly two vertex
# have odd degrees. If yes, then there is an Euler path. If not,
# raise an error (no Euler path can be found)
# if the odd condition is not meet, raise an error.
start = _find_path_start(G)
if not start:
return False
return True
def test_create_forget_node():
test_td = td.Tree_Decomposer(nx.complete_graph(2))
test_graph = nx.DiGraph()
test_root = frozenset({1, 2, 3, 4, 5})
nodes_dict = {}
nodes_dict[frozenset(test_root)] = ntd.Nice_Tree_Node(test_root)
nodes_dict[frozenset({1, 2})] = ntd.Nice_Tree_Node({1, 2})
nodes_dict[frozenset({3})] = ntd.Nice_Tree_Node({3})
nodes_dict[frozenset({1, 3})] = ntd.Nice_Tree_Node({1, 3})
nodes_dict[frozenset({2, 3})] = ntd.Nice_Tree_Node({2, 3})
nodes_dict[frozenset({1, 2, 3})] = ntd.Nice_Tree_Node({1, 2, 3})
nodes_dict[frozenset({4, 5})] = ntd.Nice_Tree_Node({4, 5})
# test 1
# checks if the function creates the correct forget nodes for
# 1 child and more than 1 vertex in parent that is not he child
test_graph.clear()
test_graph.add_edge(nodes_dict[frozenset({1, 2, 3})],
nodes_dict[frozenset(test_root)])
test_td.graph = test_graph
test_td.graph_root = nodes_dict[frozenset({1, 2, 3})]
test_td.create_forget_nodes(nodes_dict[frozenset({1, 2, 3})])
child = list(test_td.graph.successors(nodes_dict[frozenset({1, 2, 3})]))[0]
assert not child == nodes_dict[frozenset(
test_root)], "this child should be removed"
assert (child.bag == {1, 2, 3, 4}
or child.bag == {1, 2, 3, 5}), "child has not specified bag"
child_child = list(test_td.graph.successors(child))[0]
assert child_child == nodes_dict[frozenset(
test_root)], "last node should be child"
assert child_child.bag == {1, 2, 3, 4,
5}, "child_child has not specified bag"
for node_deg in list(nx.degree(test_td.graph)):
assert not node_deg[1] == 0, "does create isolated node(s)"
assert nx.number_of_selfloops(test_td.graph) == 0, "creates self loop(s)"
assert nx.is_weakly_connected(test_td.graph), "not weakly connected"
def is_dependency_subgraph(graph, subgraph_candidate,
node_attrib='label', edge_attrib='label'):
"""
returns True, if the graph contains all of the subgraph candidate's
dependency rules. The subgraph must also be (weakly) connected and contain
at least two nodes.
NOTE: The criteria used here might not be strong enough, i.e. it would
be possible to construct a subgraph candidate that contains only rules
from the graph but is not a true subgraph of the graph.
"""
if len(subgraph_candidate) > 1:
if nx.is_weakly_connected(subgraph_candidate):
if includes_all_subgraph_rules(graph, subgraph_candidate,
node_attrib=node_attrib,
edge_attrib=edge_attrib):
return True
return False
def rooted_core_interface_pairs(self, root, thickness=None, **args):
'''
Args:
root: int
thickness:
**args:
Returns:
'''
ciplist = super(self.__class__, self).rooted_core_interface_pairs(root, thickness, **args)
#numbering shards if cip graphs not connected
for cip in ciplist:
if not nx.is_weakly_connected(cip.graph):
comps = [list(node_list) for node_list in nx.weakly_connected_components(cip.graph)]
comps.sort()
for i, nodes in enumerate(comps):
for node in nodes:
cip.graph.node[node]['shard'] = i
'''
solve problem of single-ede-nodes in the core
this may replace the need for fix_structure thing
this is a little hard.. may fix later
it isnt hard if i write this code in merge_core in ubergraphlearn
for cip in ciplist:
for n,d in cip.graph.nodes(data=True):
if 'edge' in d and 'interface' not in d:
if 'interface' in cip.graph.node[ cip.graph.successors(n)[0]]:
#problem found
'''
return ciplist
def rooted_core_interface_pairs(self, root,
thickness_list=None,
for_base=False,
radius_list=[],
base_thickness_list=False):
"""
Parameters
----------
root:
thickness:
args:
Returns
-------
"""
ciplist = super(self.__class__, self).rooted_core_interface_pairs(root,
thickness_list=thickness_list,
for_base=for_base,
radius_list=radius_list,
base_thickness_list=base_thickness_list)
if not for_base:
# numbering shards if cip graphs not connected
for cip in ciplist:
if not nx.is_weakly_connected(cip.graph):
comps = [list(node_list) for node_list in nx.weakly_connected_components(cip.graph)]
comps.sort()
for i, nodes in enumerate(comps):
for node in nodes:
cip.graph.node[node]['shard'] = i
return ciplist
def edge_connectivity(G, s=None, t=None):
r"""Returns the edge connectivity of the graph or digraph G.
The edge connectivity is equal to the minimum number of edges that
must be removed to disconnect G or render it trivial. If source
and target nodes are provided, this function returns the local edge
connectivity: the minimum number of edges that must be removed to
break all paths from source to target in G.
This is a flow based implementation. The algorithm is based in solving
a number of max-flow problems (ie local st-edge connectivity, see
local_edge_connectivity) to determine the capacity of the minimum
cut on an auxiliary directed network that corresponds to the minimum
edge cut of G. It handles both directed and undirected graphs.
Parameters
----------
G : NetworkX graph
Undirected or directed graph
s : node
Source node. Optional (default=None)
t : node
Target node. Optional (default=None)
Returns
-------
K : integer
Edge connectivity for G, or local edge connectivity if source
and target were provided
Examples
--------
>>> # Platonic icosahedral graph is 5-edge-connected
>>> G = nx.icosahedral_graph()
>>> nx.edge_connectivity(G)
5
Notes
-----
This is a flow based implementation of global edge connectivity. For
undirected graphs the algorithm works by finding a 'small' dominating
set of nodes of G (see algorithm 7 in [1]_ ) and computing local max flow
(see local_edge_connectivity) between an arbitrary node in the dominating
set and the rest of nodes in it. This is an implementation of
algorithm 6 in [1]_ .
For directed graphs, the algorithm does n calls to the max flow function.
This is an implementation of algorithm 8 in [1]_ . We use the Ford and
Fulkerson algorithm to compute max flow (see ford_fulkerson).
See also
--------
local_node_connectivity
node_connectivity
local_edge_connectivity
max_flow
ford_fulkerson
References
----------
.. [1] Abdol-Hossein Esfahanian. Connectivity Algorithms.
http://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf
"""
# Local edge connectivity
if s is not None and t is not None:
if s not in G:
raise nx.NetworkXError("node %s not in graph" % s)
if t not in G:
raise nx.NetworkXError("node %s not in graph" % t)
return local_edge_connectivity(G, s, t)
# Global edge connectivity
if G.is_directed():
# Algorithm 8 in [1]
if not nx.is_weakly_connected(G):
return 0
# initial value for lambda is min degree (\delta(G))
L = min(G.degree().values())
# reuse auxiliary digraph
H = _aux_digraph_edge_connectivity(G)
nodes = G.nodes()
n = len(nodes)
for i in range(n):
try:
L = min(L, local_edge_connectivity(G, nodes[i], nodes[i + 1], aux_digraph=H))
except IndexError: # last node!
L = min(L, local_edge_connectivity(G, nodes[i], nodes[0], aux_digraph=H))
return L
else: # undirected
# Algorithm 6 in [1]
if not nx.is_connected(G):
return 0
# initial value for lambda is min degree (\delta(G))
L = min(G.degree().values())
# reuse auxiliary digraph
H = _aux_digraph_edge_connectivity(G)
# A dominating set is \lambda-covering
# We need a dominating set with at least two nodes
for node in G:
D = nx.dominating_set(G, start_with=node)
v = D.pop()
if D:
break
else:
# in complete graphs the dominating sets will always be of one node
# thus we return min degree
return L
for w in D:
L = min(L, local_edge_connectivity(G, v, w, aux_digraph=H))
return L
def node_connectivity(G, s=None, t=None, flow_func=None):
r"""Returns node connectivity for a graph or digraph G.
Node connectivity is equal to the minimum number of nodes that
must be removed to disconnect G or render it trivial. If source
and target nodes are provided, this function returns the local node
connectivity: the minimum number of nodes that must be removed to break
all paths from source to target in G.
Parameters
----------
G : NetworkX graph
Undirected graph
s : node
Source node. Optional. Default value: None.
t : node
Target node. Optional. Default value: None.
flow_func : function
A function for computing the maximum flow among a pair of nodes.
The function has to accept at least three parameters: a Digraph,
a source node, and a target node. And return a residual network
that follows NetworkX conventions (see :meth:`maximum_flow` for
details). If flow_func is None, the default maximum flow function
(:meth:`edmonds_karp`) is used. See below for details. The
choice of the default function may change from version
to version and should not be relied on. Default value: None.
Returns
-------
K : integer
Node connectivity of G, or local node connectivity if source
and target are provided.
Examples
--------
>>> # Platonic icosahedral graph is 5-node-connected
>>> G = nx.icosahedral_graph()
>>> nx.node_connectivity(G)
5
You can use alternative flow algorithms for the underlying maximum
flow computation. In dense networks the algorithm
:meth:`shortest_augmenting_path` will usually perform better
than the default :meth:`edmonds_karp`, which is faster for
sparse networks with highly skewed degree distributions. Alternative
flow functions have to be explicitly imported from the flow package.
>>> from networkx.algorithms.flow import shortest_augmenting_path
>>> nx.node_connectivity(G, flow_func=shortest_augmenting_path)
5
If you specify a pair of nodes (source and target) as parameters,
this function returns the value of local node connectivity.
>>> nx.node_connectivity(G, 3, 7)
5
If you need to perform several local computations among different
pairs of nodes on the same graph, it is recommended that you reuse
the data structures used in the maximum flow computations. See
:meth:`local_node_connectivity` for details.
Notes
-----
This is a flow based implementation of node connectivity. The
algorithm works by solving `O((n-\delta-1+\delta(\delta-1)/2))`
maximum flow problems on an auxiliary digraph. Where `\delta`
is the minimum degree of G. For details about the auxiliary
digraph and the computation of local node connectivity see
:meth:`local_node_connectivity`. This implementation is based
on algorithm 11 in [1]_.
See also
--------
:meth:`local_node_connectivity`
:meth:`edge_connectivity`
:meth:`maximum_flow`
:meth:`edmonds_karp`
:meth:`preflow_push`
:meth:`shortest_augmenting_path`
References
----------
.. [1] Abdol-Hossein Esfahanian. Connectivity Algorithms.
http://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf
"""
if (s is not None and t is None) or (s is None and t is not None):
raise nx.NetworkXError('Both source and target must be specified.')
# Local node connectivity
if s is not None and t is not None:
if s not in G:
raise nx.NetworkXError('node %s not in graph' % s)
if t not in G:
raise nx.NetworkXError('node %s not in graph' % t)
return local_node_connectivity(G, s, t, flow_func=flow_func)
# Global node connectivity
if G.is_directed():
if not nx.is_weakly_connected(G):
return 0
iter_func = itertools.permutations
# It is necessary to consider both predecessors
# and successors for directed graphs
def neighbors(v):
return itertools.chain.from_iterable([G.predecessors_iter(v),
G.successors_iter(v)])
else:
if not nx.is_connected(G):
return 0
iter_func = itertools.combinations
neighbors = G.neighbors_iter
# Reuse the auxiliary digraph and the residual network
H = build_auxiliary_node_connectivity(G)
R = build_residual_network(H, 'capacity')
kwargs = dict(flow_func=flow_func, auxiliary=H, residual=R)
# Pick a node with minimum degree
degree = G.degree()
minimum_degree = min(degree.values())
v = next(n for n, d in degree.items() if d == minimum_degree)
# Node connectivity is bounded by degree.
K = minimum_degree
# compute local node connectivity with all its non-neighbors nodes
for w in set(G) - set(neighbors(v)) - set([v]):
kwargs['cutoff'] = K
K = min(K, local_node_connectivity(G, v, w, **kwargs))
# Also for non adjacent pairs of neighbors of v
for x, y in iter_func(neighbors(v), 2):
if y in G[x]:
continue
kwargs['cutoff'] = K
K = min(K, local_node_connectivity(G, x, y, **kwargs))
return K
pos=nx.spring_layout(G,k=0.15,iterations=10)
# pos=nx.graphviz_layout(G)
# pos=layout(G)
G.remove_nodes_from(nx.isolates(G))
print str(" ")
print 'WEAK CONNECTEDNESS OF DIRECTED GRAPHS'
print str(" ")
print str(" ")
print G.name
print str(" ")
print 'Is graph G weakly connected?', nx.is_weakly_connected(G)
print 'The number of weakly connected components of G is:', nx.number_weakly_connected_components(G)
print str(" ")
lc=sorted(nx.weakly_connected_components(G), key = len, reverse=True)
print 'List of weakly connected components:'
# print sorted(nx.weakly_connected_components(G), key = len, reverse=True)
print lc
print str(" ")
deg=G.degree()
deg_dic=[]
for nd in deg:
if deg[nd]>0:
deg_dic.append(nd)
def test_is_not_consistent_dag_weakly_connected(self):
g = self._createBaseGraph([(1,2),(1,3)])
self.assertTrue(nx.is_weakly_connected(g))
def test_is_dag_connected(self):
g = self._createBaseGraph([(1,2),(2,3),(1,3),(4,5)])
self.assertFalse(nx.is_weakly_connected(g))
def average_shortest_path_length(G, weight=None):
r"""Return the average shortest path length.
The average shortest path length is
.. math::
a =\sum_{s,t \in V} \frac{d(s, t)}{n(n-1)}
where `V` is the set of nodes in `G`,
`d(s, t)` is the shortest path from `s` to `t`,
and `n` is the number of nodes in `G`.
Parameters
----------
G : NetworkX graph
weight : None or string, optional (default = None)
If None, every edge has weight/distance/cost 1.
If a string, use this edge attribute as the edge weight.
Any edge attribute not present defaults to 1.
Raises
------
NetworkXPointlessConcept
If `G` is the null graph (that is, the graph on zero nodes).
NetworkXError
If `G` is not connected (or not weakly connected, in the case
of a directed graph).
Examples
--------
>>> G = nx.path_graph(5)
>>> nx.average_shortest_path_length(G)
2.0
For disconnected graphs, you can compute the average shortest path
length for each component
>>> G = nx.Graph([(1, 2), (3, 4)])
>>> for C in nx.connected_component_subgraphs(G):
... print(nx.average_shortest_path_length(C))
1.0
1.0
"""
n = len(G)
# For the special case of the null graph, raise an exception, since
# there are no paths in the null graph.
if n == 0:
msg = ('the null graph has no paths, thus there is no average'
'shortest path length')
raise nx.NetworkXPointlessConcept(msg)
# For the special case of the trivial graph, return zero immediately.
if n == 1:
return 0
# Shortest path length is undefined if the graph is disconnected.
if G.is_directed() and not nx.is_weakly_connected(G):
raise nx.NetworkXError("Graph is not weakly connected.")
if not G.is_directed() and not nx.is_connected(G):
raise nx.NetworkXError("Graph is not connected.")
# Compute all-pairs shortest paths.
if weight is None:
path_length = lambda v: nx.single_source_shortest_path_length(G, v)
else:
ssdpl = nx.single_source_dijkstra_path_length
path_length = lambda v: ssdpl(G, v, weight=weight)
# Sum the distances for each (ordered) pair of source and target node.
s = sum(l for u in G for v, l in path_length(u))
return s / (n * (n - 1))
def node_connectivity(G, s=None, t=None):
r"""Returns node connectivity for a graph or digraph G.
Node connectivity is equal to the minimum number of nodes that
must be removed to disconnect G or render it trivial. If source
and target nodes are provided, this function returns the local node
connectivity: the minimum number of nodes that must be removed to break
all paths from source to target in G.
This is a flow based implementation. The algorithm is based in
solving a number of max-flow problems (ie local st-node connectivity,
see local_node_connectivity) to determine the capacity of the
minimum cut on an auxiliary directed network that corresponds to the
minimum node cut of G. It handles both directed and undirected graphs.
Parameters
----------
G : NetworkX graph
Undirected graph
s : node
Source node. Optional (default=None)
t : node
Target node. Optional (default=None)
Returns
-------
K : integer
Node connectivity of G, or local node connectivity if source
and target were provided
Examples
--------
>>> # Platonic icosahedral graph is 5-node-connected
>>> G = nx.icosahedral_graph()
>>> nx.node_connectivity(G)
5
>>> nx.node_connectivity(G, 3, 7)
5
Notes
-----
This is a flow based implementation of node connectivity. The
algorithm works by solving `O((n-\delta-1+\delta(\delta-1)/2)` max-flow
problems on an auxiliary digraph. Where `\delta` is the minimum degree
of G. For details about the auxiliary digraph and the computation of
local node connectivity see local_node_connectivity.
This implementation is based on algorithm 11 in [1]_. We use the Ford
and Fulkerson algorithm to compute max flow (see ford_fulkerson).
See also
--------
local_node_connectivity
all_pairs_node_connectivity_matrix
local_edge_connectivity
edge_connectivity
max_flow
ford_fulkerson
References
----------
.. [1] Abdol-Hossein Esfahanian. Connectivity Algorithms.
http://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf
"""
# Local node connectivity
if s is not None and t is not None:
if s not in G:
raise nx.NetworkXError("node %s not in graph" % s)
if t not in G:
raise nx.NetworkXError("node %s not in graph" % t)
return local_node_connectivity(G, s, t)
# Global node connectivity
if G.is_directed():
if not nx.is_weakly_connected(G):
return 0
iter_func = itertools.permutations
# I think that it is necessary to consider both predecessors
# and successors for directed graphs
def neighbors(v):
return itertools.chain.from_iterable([G.predecessors_iter(v), G.successors_iter(v)])
else:
if not nx.is_connected(G):
return 0
iter_func = itertools.combinations
neighbors = G.neighbors_iter
# Initial guess \kappa = n - 1
K = G.order() - 1
deg = G.degree()
min_deg = min(deg.values())
v = next(n for n, d in deg.items() if d == min_deg)
# Reuse the auxiliary digraph
H, mapping = _aux_digraph_node_connectivity(G)
# compute local node connectivity with all non-neighbors nodes
for w in set(G) - set(neighbors(v)) - set([v]):
K = min(K, local_node_connectivity(G, v, w, aux_digraph=H, mapping=mapping))
# Same for non adjacent pairs of neighbors of v
for x, y in iter_func(neighbors(v), 2):
if y in G[x]:
continue
K = min(K, local_node_connectivity(G, x, y, aux_digraph=H, mapping=mapping))
return K
def minimum_edge_cut(G, s=None, t=None, flow_func=None):
r"""Returns a set of edges of minimum cardinality that disconnects G.
If source and target nodes are provided, this function returns the
set of edges of minimum cardinality that, if removed, would break
all paths among source and target in G. If not, it returns a set of
edges of minimum cardinality that disconnects G.
Parameters
----------
G : NetworkX graph
s : node
Source node. Optional. Default value: None.
t : node
Target node. Optional. Default value: None.
flow_func : function
A function for computing the maximum flow among a pair of nodes.
The function has to accept at least three parameters: a Digraph,
a source node, and a target node. And return a residual network
that follows NetworkX conventions (see :meth:`maximum_flow` for
details). If flow_func is None, the default maximum flow function
(:meth:`edmonds_karp`) is used. See below for details. The
choice of the default function may change from version
to version and should not be relied on. Default value: None.
Returns
-------
cutset : set
Set of edges that, if removed, would disconnect G. If source
and target nodes are provided, the set contians the edges that
if removed, would destroy all paths between source and target.
Examples
--------
>>> # Platonic icosahedral graph has edge connectivity 5
>>> G = nx.icosahedral_graph()
>>> len(nx.minimum_edge_cut(G))
5
You can use alternative flow algorithms for the underlying
maximum flow computation. In dense networks the algorithm
:meth:`shortest_augmenting_path` will usually perform better
than the default :meth:`edmonds_karp`, which is faster for
sparse networks with highly skewed degree distributions.
Alternative flow functions have to be explicitly imported
from the flow package.
>>> from networkx.algorithms.flow import shortest_augmenting_path
>>> len(nx.minimum_edge_cut(G, flow_func=shortest_augmenting_path))
5
If you specify a pair of nodes (source and target) as parameters,
this function returns the value of local edge connectivity.
>>> nx.edge_connectivity(G, 3, 7)
5
If you need to perform several local computations among different
pairs of nodes on the same graph, it is recommended that you reuse
the data structures used in the maximum flow computations. See
:meth:`local_edge_connectivity` for details.
Notes
-----
This is a flow based implementation of minimum edge cut. For
undirected graphs the algorithm works by finding a 'small' dominating
set of nodes of G (see algorithm 7 in [1]_) and computing the maximum
flow between an arbitrary node in the dominating set and the rest of
nodes in it. This is an implementation of algorithm 6 in [1]_. For
directed graphs, the algorithm does n calls to the max flow function.
The function raises an error if the directed graph is not weakly
connected and returns an empty set if it is weakly connected.
It is an implementation of algorithm 8 in [1]_.
See also
--------
:meth:`minimum_st_edge_cut`
:meth:`minimum_node_cut`
:meth:`stoer_wagner`
:meth:`node_connectivity`
:meth:`edge_connectivity`
:meth:`maximum_flow`
:meth:`edmonds_karp`
:meth:`preflow_push`
:meth:`shortest_augmenting_path`
References
----------
.. [1] Abdol-Hossein Esfahanian. Connectivity Algorithms.
http://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf
"""
if (s is not None and t is None) or (s is None and t is not None):
raise nx.NetworkXError("Both source and target must be specified.")
# reuse auxiliary digraph and residual network
H = build_auxiliary_edge_connectivity(G)
R = build_residual_network(H, "capacity")
kwargs = dict(flow_func=flow_func, residual=R, auxiliary=H)
# Local minimum edge cut if s and t are not None
if s is not None and t is not None:
if s not in G:
raise nx.NetworkXError("node %s not in graph" % s)
if t not in G:
raise nx.NetworkXError("node %s not in graph" % t)
return minimum_st_edge_cut(H, s, t, **kwargs)
# Global minimum edge cut
# Analog to the algoritm for global edge connectivity
if G.is_directed():
# Based on algorithm 8 in [1]
if not nx.is_weakly_connected(G):
raise nx.NetworkXError("Input graph is not connected")
# Initial cutset is all edges of a node with minimum degree
node = min(G, key=G.degree)
min_cut = set(G.edges(node))
nodes = list(G)
n = len(nodes)
for i in range(n):
try:
this_cut = minimum_st_edge_cut(H, nodes[i], nodes[i + 1], **kwargs)
if len(this_cut) <= len(min_cut):
min_cut = this_cut
except IndexError: # Last node!
this_cut = minimum_st_edge_cut(H, nodes[i], nodes[0], **kwargs)
if len(this_cut) <= len(min_cut):
min_cut = this_cut
return min_cut
else: # undirected
# Based on algorithm 6 in [1]
if not nx.is_connected(G):
raise nx.NetworkXError("Input graph is not connected")
# Initial cutset is all edges of a node with minimum degree
node = min(G, key=G.degree)
min_cut = set(G.edges(node))
# A dominating set is \lambda-covering
# We need a dominating set with at least two nodes
for node in G:
D = nx.dominating_set(G, start_with=node)
v = D.pop()
if D:
break
else:
# in complete graphs the dominating set will always be of one node
# thus we return min_cut, which now contains the edges of a node
# with minimum degree
return min_cut
for w in D:
this_cut = minimum_st_edge_cut(H, v, w, **kwargs)
if len(this_cut) <= len(min_cut):
min_cut = this_cut
return min_cut
def minimum_node_cut(G, s=None, t=None, flow_func=None):
r"""Returns a set of nodes of minimum cardinality that disconnects G.
If source and target nodes are provided, this function returns the
set of nodes of minimum cardinality that, if removed, would destroy
all paths among source and target in G. If not, it returns a set
of nodes of minimum cardinality that disconnects G.
Parameters
----------
G : NetworkX graph
s : node
Source node. Optional. Default value: None.
t : node
Target node. Optional. Default value: None.
flow_func : function
A function for computing the maximum flow among a pair of nodes.
The function has to accept at least three parameters: a Digraph,
a source node, and a target node. And return a residual network
that follows NetworkX conventions (see :meth:`maximum_flow` for
details). If flow_func is None, the default maximum flow function
(:meth:`edmonds_karp`) is used. See below for details. The
choice of the default function may change from version
to version and should not be relied on. Default value: None.
Returns
-------
cutset : set
Set of nodes that, if removed, would disconnect G. If source
and target nodes are provided, the set contians the nodes that
if removed, would destroy all paths between source and target.
Examples
--------
>>> # Platonic icosahedral graph has node connectivity 5
>>> G = nx.icosahedral_graph()
>>> node_cut = nx.minimum_node_cut(G)
>>> len(node_cut)
5
You can use alternative flow algorithms for the underlying maximum
flow computation. In dense networks the algorithm
:meth:`shortest_augmenting_path` will usually perform better
than the default :meth:`edmonds_karp`, which is faster for
sparse networks with highly skewed degree distributions. Alternative
flow functions have to be explicitly imported from the flow package.
>>> from networkx.algorithms.flow import shortest_augmenting_path
>>> node_cut == nx.minimum_node_cut(G, flow_func=shortest_augmenting_path)
True
If you specify a pair of nodes (source and target) as parameters,
this function returns a local st node cut.
>>> len(nx.minimum_node_cut(G, 3, 7))
5
If you need to perform several local st cuts among different
pairs of nodes on the same graph, it is recommended that you reuse
the data structures used in the maximum flow computations. See
:meth:`minimum_st_node_cut` for details.
Notes
-----
This is a flow based implementation of minimum node cut. The algorithm
is based in solving a number of maximum flow computations to determine
the capacity of the minimum cut on an auxiliary directed network that
corresponds to the minimum node cut of G. It handles both directed
and undirected graphs. This implementation is based on algorithm 11
in [1]_.
See also
--------
:meth:`minimum_st_node_cut`
:meth:`minimum_cut`
:meth:`minimum_edge_cut`
:meth:`stoer_wagner`
:meth:`node_connectivity`
:meth:`edge_connectivity`
:meth:`maximum_flow`
:meth:`edmonds_karp`
:meth:`preflow_push`
:meth:`shortest_augmenting_path`
References
----------
.. [1] Abdol-Hossein Esfahanian. Connectivity Algorithms.
http://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf
"""
if (s is not None and t is None) or (s is None and t is not None):
raise nx.NetworkXError("Both source and target must be specified.")
# Local minimum node cut.
if s is not None and t is not None:
if s not in G:
raise nx.NetworkXError("node %s not in graph" % s)
if t not in G:
raise nx.NetworkXError("node %s not in graph" % t)
return minimum_st_node_cut(G, s, t, flow_func=flow_func)
# Global minimum node cut.
# Analog to the algoritm 11 for global node connectivity in [1].
if G.is_directed():
if not nx.is_weakly_connected(G):
raise nx.NetworkXError("Input graph is not connected")
iter_func = itertools.permutations
def neighbors(v):
return itertools.chain.from_iterable([G.predecessors(v), G.successors(v)])
else:
if not nx.is_connected(G):
raise nx.NetworkXError("Input graph is not connected")
iter_func = itertools.combinations
neighbors = G.neighbors
# Reuse the auxiliary digraph and the residual network.
H = build_auxiliary_node_connectivity(G)
R = build_residual_network(H, "capacity")
kwargs = dict(flow_func=flow_func, auxiliary=H, residual=R)
# Choose a node with minimum degree.
v = min(G, key=G.degree)
# Initial node cutset is all neighbors of the node with minimum degree.
min_cut = set(G[v])
# Compute st node cuts between v and all its non-neighbors nodes in G.
for w in set(G) - set(neighbors(v)) - set([v]):
this_cut = minimum_st_node_cut(G, v, w, **kwargs)
if len(min_cut) >= len(this_cut):
min_cut = this_cut
# Also for non adjacent pairs of neighbors of v.
for x, y in iter_func(neighbors(v), 2):
if y in G[x]:
continue
this_cut = minimum_st_node_cut(G, x, y, **kwargs)
if len(min_cut) >= len(this_cut):
min_cut = this_cut
return min_cut
def edge_connectivity(G, s=None, t=None, flow_func=None):
r"""Returns the edge connectivity of the graph or digraph G.
The edge connectivity is equal to the minimum number of edges that
must be removed to disconnect G or render it trivial. If source
and target nodes are provided, this function returns the local edge
connectivity: the minimum number of edges that must be removed to
break all paths from source to target in G.
Parameters
----------
G : NetworkX graph
Undirected or directed graph
s : node
Source node. Optional. Default value: None.
t : node
Target node. Optional. Default value: None.
flow_func : function
A function for computing the maximum flow among a pair of nodes.
The function has to accept at least three parameters: a Digraph,
a source node, and a target node. And return a residual network
that follows NetworkX conventions (see :meth:`maximum_flow` for
details). If flow_func is None, the default maximum flow function
(:meth:`edmonds_karp`) is used. See below for details. The
choice of the default function may change from version
to version and should not be relied on. Default value: None.
Returns
-------
K : integer
Edge connectivity for G, or local edge connectivity if source
and target were provided
Examples
--------
>>> # Platonic icosahedral graph is 5-edge-connected
>>> G = nx.icosahedral_graph()
>>> nx.edge_connectivity(G)
5
You can use alternative flow algorithms for the underlying
maximum flow computation. In dense networks the algorithm
:meth:`shortest_augmenting_path` will usually perform better
than the default :meth:`edmonds_karp`, which is faster for
sparse networks with highly skewed degree distributions.
Alternative flow functions have to be explicitly imported
from the flow package.
>>> from networkx.algorithms.flow import shortest_augmenting_path
>>> nx.edge_connectivity(G, flow_func=shortest_augmenting_path)
5
If you specify a pair of nodes (source and target) as parameters,
this function returns the value of local edge connectivity.
>>> nx.edge_connectivity(G, 3, 7)
5
If you need to perform several local computations among different
pairs of nodes on the same graph, it is recommended that you reuse
the data structures used in the maximum flow computations. See
:meth:`local_edge_connectivity` for details.
Notes
-----
This is a flow based implementation of global edge connectivity.
For undirected graphs the algorithm works by finding a 'small'
dominating set of nodes of G (see algorithm 7 in [1]_ ) and
computing local maximum flow (see :meth:`local_edge_connectivity`)
between an arbitrary node in the dominating set and the rest of
nodes in it. This is an implementation of algorithm 6 in [1]_ .
For directed graphs, the algorithm does n calls to the maximum
flow function. This is an implementation of algorithm 8 in [1]_ .
See also
--------
:meth:`local_edge_connectivity`
:meth:`local_node_connectivity`
:meth:`node_connectivity`
:meth:`maximum_flow`
:meth:`edmonds_karp`
:meth:`preflow_push`
:meth:`shortest_augmenting_path`
References
----------
.. [1] Abdol-Hossein Esfahanian. Connectivity Algorithms.
http://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf
"""
if (s is not None and t is None) or (s is None and t is not None):
raise nx.NetworkXError('Both source and target must be specified.')
# Local edge connectivity
if s is not None and t is not None:
if s not in G:
raise nx.NetworkXError('node %s not in graph' % s)
if t not in G:
raise nx.NetworkXError('node %s not in graph' % t)
return local_edge_connectivity(G, s, t, flow_func=flow_func)
# Global edge connectivity
# reuse auxiliary digraph and residual network
H = build_auxiliary_edge_connectivity(G)
R = build_residual_network(H, 'capacity')
kwargs = dict(flow_func=flow_func, auxiliary=H, residual=R)
if G.is_directed():
# Algorithm 8 in [1]
if not nx.is_weakly_connected(G):
return 0
# initial value for \lambda is minimum degree
L = min(G.degree().values())
nodes = G.nodes()
n = len(nodes)
for i in range(n):
kwargs['cutoff'] = L
try:
L = min(L, local_edge_connectivity(G, nodes[i], nodes[i+1],
**kwargs))
except IndexError: # last node!
L = min(L, local_edge_connectivity(G, nodes[i], nodes[0],
**kwargs))
return L
else: # undirected
# Algorithm 6 in [1]
if not nx.is_connected(G):
return 0
# initial value for \lambda is minimum degree
L = min(G.degree().values())
# A dominating set is \lambda-covering
# We need a dominating set with at least two nodes
for node in G:
D = nx.dominating_set(G, start_with=node)
v = D.pop()
if D:
break
else:
# in complete graphs the dominating sets will always be of one node
# thus we return min degree
return L
for w in D:
kwargs['cutoff'] = L
L = min(L, local_edge_connectivity(G, v, w, **kwargs))
return L
def test_is_weakly_connected(self):
for G, C in self.gc:
U = G.to_undirected()
assert_equal(nx.is_weakly_connected(G), nx.is_connected(U))