def test_minimal_spanning_tree_with_negative_weigths(self):
gr = graph()
gr.add_nodes((0,1,2,3))
gr.add_edge((0,1), wt=-0.4)
gr.add_edge((1,2), wt=-0.6)
gr.add_edge((2,0), wt=-0.5)
gr.add_edge((3,2), wt=-0.1)
gr.add_edge((3,1), wt=-0.2)
print minimal_spanning_tree(gr, 0)
def duplicate_component(graph, node):
"""
Duplicates component in a graph
@type graph: GraphWrapper
@param graph: the graph in which to duplicate the component
@type node: graph_representation.node.Node
@param node: node which roots the component to be duplicated
@rtype Node
@return the duplicated node of the input node, which roots the duplicated component
"""
nodesMap = {}
nodes = minimal_spanning_tree(graph=graph, root=node)
for curNode in nodes:
dupNode = duplicate_node(graph=graph,
node=curNode,
connectToNeighbours=False)
nodesMap[curNode.uid] = dupNode
for curNode in nodes:
curDupNode = nodesMap[curNode.uid]
for curNeighbour in graph.neighbors(curNode):
curDupNeighbour = nodesMap[curNeighbour.uid]
graph.add_edge(edge=(curDupNode, curDupNeighbour),
label=graph.edge_label((curNode, curNeighbour)))
return nodesMap[node.uid]
def duplicate_component(graph, node):
"""
Duplicates component in a graph
@type graph: GraphWrapper
@param graph: the graph in which to duplicate the component
@type node: graph_representation.node.Node
@param node: node which roots the component to be duplicated
@rtype Node
@return the duplicated node of the input node, which roots the duplicated component
"""
nodesMap = {}
nodes = minimal_spanning_tree(graph=graph,
root=node)
for curNode in nodes:
dupNode = duplicate_node(graph=graph,
node=curNode,
connectToNeighbours=False)
nodesMap[curNode.uid] = dupNode
for curNode in nodes:
curDupNode = nodesMap[curNode.uid]
for curNeighbour in graph.neighbors(curNode):
curDupNeighbour = nodesMap[curNeighbour.uid]
graph.add_edge(edge=(curDupNode, curDupNeighbour),
label=graph.edge_label((curNode, curNeighbour)))
return nodesMap[node.uid]
def test_minimal_spanning_tree_on_graph(self):
gr = testlib.new_graph(wt_range=(1,10))
mst = minimal_spanning_tree(gr, root=0)
wt = tree_weight(gr, mst)
len_dfs = len(depth_first_search(gr, root=0)[0])
for each in mst:
if (mst[each] != None):
mst_copy = deepcopy(mst)
del(mst_copy[each])
for other in gr[each]:
mst_copy[each] = other
if (tree_weight(gr, mst_copy) < wt):
gr2 = graph()
add_spanning_tree(gr2, mst_copy)
assert len(depth_first_search(gr2, root=0)[0]) < len_dfs
def delete_component(graph, node):
"""
deletes component in a graph
@type graph: GraphWrapper
@param graph: the graph in which to delete the component
@type node: graph_representation.node.Node
@param node: node which roots the component to be deleted
"""
nodes = minimal_spanning_tree(graph=graph, root=node)
for node in nodes:
graph.del_node(node)
def test_minimal_spanning_tree_on_graph(self):
gr = new_graph(wt_range=(1,10))
mst = minimal_spanning_tree(gr, root=0)
wt = tree_weight(gr, mst)
len_dfs = len(depth_first_search(gr, root=0)[0])
for each in mst:
if (mst[each] != None):
mst_copy = deepcopy(mst)
del(mst_copy[each])
for other in gr[each]:
mst_copy[each] = other
if (tree_weight(gr, mst_copy) < wt):
gr2 = graph()
add_spanning_tree(gr2, mst_copy)
assert len(depth_first_search(gr2, root=0)[0]) < len_dfs
def delete_component(graph, node):
"""
deletes component in a graph
@type graph: GraphWrapper
@param graph: the graph in which to delete the component
@type node: graph_representation.node.Node
@param node: node which roots the component to be deleted
"""
nodes = minimal_spanning_tree(graph=graph,
root=node)
for node in nodes:
graph.del_node(node)
def component_to_string(graph, node):
"""
get a textual value of a component in a graph
@type graph: GraphWrapper
@param graph: the graph in which to delete the component
@type node: graph_representation.node.Node
@param node: node which roots the component
"""
nodes = minimal_spanning_tree(graph=graph, root=node)
texts = []
for node in nodes:
texts.extend([w for w in node.get_text(graph) if w.index != NO_INDEX])
chars = '\'\"-,.:;!? '
return " ".join([w.word for w in sorted(texts, key=lambda w: w.index)
]).rstrip(chars).lstrip(chars)
def minimal_spanning_tree(weighted_graph):
"""
Return the minimal spanning tree of a weighted graph.
Wraps pygraph's minimal spanning tree.
"""
min_weight = min(weighted_graph.edge_weight(edge)
for edge in weighted_graph.edges())
if min_weight < 0:
reweighted_graph = Graph.undirected()
reweighted_graph.add_graph(weighted_graph)
for edge in weighted_graph.edges():
weight = weighted_graph.edge_weight(edge)
reweighted_graph.set_edge_weight(edge, weight - min_weight)
return Graph.minimal_spanning_tree(reweighted_graph)
min_tree = Graph.directed()
min_tree.add_nodes(weighted_graph.nodes())
for edge in minimal_spanning_tree(weighted_graph).items():
if not None in edge:
min_tree.add_edge(edge)
return min_tree
def component_to_string(graph, node):
"""
get a textual value of a component in a graph
@type graph: GraphWrapper
@param graph: the graph in which to delete the component
@type node: graph_representation.node.Node
@param node: node which roots the component
"""
nodes = minimal_spanning_tree(graph=graph,
root=node)
texts = []
for node in nodes:
texts.extend([w for w in node.get_text(graph) if w.index != NO_INDEX])
chars = '\'\"-,.:;!? '
return " ".join([w.word for w in sorted(texts, key=lambda w:w.index)]).rstrip(chars).lstrip(chars)
if DEBUG:
print(row, col, cost)
g = graph()
g.add_nodes(range(N))
for r in xrange(N):
for c in xrange(r,N):
if matrix[r][c] != 0:
g.add_edge((r,c), matrix[r][c])
if DEBUG:
print(r, c, matrix[r][c])
st = minimal_spanning_tree(g)
ming = graph()
ming.add_spanning_tree(st)
if DEBUG:
print(st)
print()
print(ming)
print()
print(total_weight(g,g))
print(total_weight(ming,g))
print(total_weight(g,g) - total_weight(ming,g))
