def remove(self, vertices):
"""Remove vertices from the graph."""
if not vertices in self.vertices:
raise ValueError('Graph don\'t contain some of [{}]'.format(vertices))
for v in iterate(vertices):
for w in iterate(self(v)):
self.disconnect(v, w)
self._vertices -= vertices
for v in iterate(vertices):
del self.neighborhoods[v]
def generate_random(nr_vertices, nr_edges=0):
if not 0 <= nr_edges <= nr_vertices * (nr_vertices - 1) / 2:
raise ValueError
if not nr_edges:
nr_edges = 0.5
graph = Graph()
graph.add(bits(*range(nr_vertices)))
if nr_edges < 1:
# Add random edges between groups
for v in graph:
for w in graph:
if v < w and random() < nr_edges:
graph.connect(v, w)
return graph
else:
vertex_list = list(iterate(graph.vertices))
for _ in range(nr_edges):
while 1:
v, w = sample(vertex_list, 2)
# Don't connect vertices twice
if not w in graph[v]:
break
graph.connect(v, w)
return graph
def __call__(self, vertices):
"""Return the union of neighborhoods of vertices."""
result = 0
for v in iterate(vertices):
result = result | self.neighborhoods[v]
#result |= self.neighborhoods[v]
return result
def components(graph):
"""Return a list of the connected components of in the graph."""
done = 0
for v in iterate(graph.vertices):
if contains(done, v):
continue
component = sum(bfs(graph, v))
yield component
done |= component
def add(self, vertices):
"""Add new vertices to the graph."""
assert isinstance(vertices, int)
if not disjoint(self.vertices, vertices):
raise ValueError('Graph already contain some of [{}]'.format(vertices))
self._vertices |= vertices
for v in iterate(vertices):
self.neighborhoods[v] = 0
def greedy_step(G, left, right, un_left, booldim_left, un_table, bound):
best_vertex = None
best_booldim = Infinity
best_un = None
if size(right) == 1:
return right, {0}, 1
assert size(right) > 1
candidates = get_neighborhood_2(G.neighborhoods, left) & right
# Trivial cases are slow
for v in iterate(candidates):
if trivial_case(G.neighborhoods, left, right, v):
new_un = increment_un(G, left, un_left, v)
new_booldim = len(new_un)
return v, new_un, new_booldim
for v in iterate(candidates):
if left | v not in un_table:
un_table[left | v] = increment_un(G, left, un_left, v)
new_un = un_table[left | v]
new_booldim = len(new_un)
# Apply pruning
if new_booldim >= bound:
# print('pruning')
continue
if new_booldim < best_booldim:
best_vertex = v
best_booldim = new_booldim
best_un = new_un
# If nothing found
if best_vertex == None:
best_un = increment_un(G, left, un_left, v)
best_booldim = len(best_un)
best_vertex = v
assert best_vertex != None
return best_vertex, best_un, best_booldim
def is_word_in_graph(word: str, graph, last_vertex=0, forbidden_vertices=0):
if not word:
return True
letter = word[0]
candidates = graph.letters_to_vertices[letter] | graph.letters_to_vertices['.']
candidates = subtract(candidates, forbidden_vertices)
if last_vertex:
candidates &= graph.neighborhoods[last_vertex]
return any(is_word_in_graph(word[1:], graph, v, forbidden_vertices | v) for v in iterate(candidates))
def is_word_in_graph(word: str, graph):
if not word:
return False
letter = word[0]
candidates = (graph.letters_to_vertices[letter]
if letter in graph.letters_to_vertices else 0)
if not candidates:
return False
return any(recurse(word[1:], graph, v, v) for v in iterate(candidates))
def trivial_case(N, left, right, v):
# No neighbors
if contains(left, N[v]):
return True
# Twins
for u in iterate(left):
if N[v] & right == subtract(N[u], v) & right:
return True
return False
def contract(self, v):
"""Contract a vertex."""
if not v in self:
raise ValueError
neighbors = list(iterate(self(v)))
self.remove(v)
for w1 in neighbors:
for w2 in neighbors:
if w1 < w2 and not w1 in self[w2]:
self.connect(w1, w2)
def recurse(word: str, graph, last_vertex, forbidden):
if not word:
return True
letter = word[0]
if letter not in graph.letters_to_vertices:
return False
candidates = subtract(graph.letters_to_vertices[letter] &
graph.neighborhoods[last_vertex], forbidden)
if not candidates:
return False
return any(recurse(word[1:], graph, v, forbidden | v) for v in iterate(candidates))
def heuristic(graph):
subset = 0
while is_independent(graph, subset):
# Find valid vertex with the least new neighbors
existing_neighbors = graph(subset)
min_new_neighbors = Infinity
new_vertex = None
for v in iterate(subtract(graph.vertices, subset)):
if not graph(v) & subset:
new_neighbors = subtract(graph(v), existing_neighbors)
if size(new_neighbors) < min_new_neighbors:
min_new_neighbors = size(new_neighbors)
new_vertex = v
if new_vertex == None:
return subset
else:
subset |= new_vertex
def verify_symmetry(self):
for v in self:
for w in iterate(self(v)):
assert v in self(w)
def get_neighborhood_2(N, subset):
result = get_neighborhood(N, subset)
for v in iterate(result):
result |= N[v]
return result
def edges(self):
"""Iterate over each pair of connected vertices exactly once."""
for v in self:
for w in iterate(self(v)):
if w < v:
yield v, w
def is_independent(graph, subset):
for v in iterate(subset):
for w in iterate(subset):
if v > w and graph(v) & w:
return False
return True
def get_neighborhood(N, subset):
result = 0
for v in iterate(subset):
result |= N[v]
return result
def __iter__(self):
"""Iterate over all vertices."""
return iterate(self.vertices)
def __repr__(self):
return 'vertices: {}'.format(list(iterate(self.vertices)))
