def min_steiner_tree(g,
obs_nodes,
p=None,
return_type='tree',
debug=False,
verbose=False):
assert len(obs_nodes) > 0, 'no terminals'
if g.num_vertices() == len(obs_nodes):
print('it\'s a minimum spanning tree problem')
gc, eweight, r2pred = build_closure(g,
obs_nodes,
p=p,
debug=debug,
verbose=verbose)
# print('gc', gc)
tree_map = min_spanning_tree(gc, eweight, root=None)
tree = GraphView(gc, directed=False, efilt=tree_map)
tree_edges = set()
for e in tree.edges():
u, v = map(int, e)
recovered_edges = extract_edges_from_pred(u, v, r2pred[u])
assert recovered_edges, 'empty!'
for i, j in recovered_edges:
tree_edges.add((i, j))
tree_nodes = list(set(itertools.chain(*tree_edges)))
if return_type == 'nodes':
return tree_nodes
elif return_type == 'edges':
return list(map(edge2tuple, tree_edges))
elif return_type == 'tree':
vfilt = g.new_vertex_property('bool')
vfilt.set_value(False)
for n in tree_nodes:
vfilt[n] = True
efilt = g.new_edge_property('bool')
for i, j in tree_edges:
efilt[g.edge(i, j)] = 1
subg = GraphView(g, efilt=efilt, vfilt=vfilt, directed=False)
if p is not None:
weights = subg.new_edge_property('float')
for e in subg.edges():
weights[e] = p[e]
else:
weights = None
# remove cycles
tree_map = min_spanning_tree(subg, weights, root=None)
t = GraphView(g, directed=False, vfilt=vfilt, efilt=tree_map)
return t
def min_steiner_tree(g, obs_nodes, debug=False, verbose=False):
if g.num_vertices() == len(obs_nodes):
print('it\'s a minimum spanning tree problem')
gc, eweight, r2pred = build_closure(g,
obs_nodes,
debug=debug,
verbose=verbose)
# print('gc', gc)
tree_map = min_spanning_tree(gc, eweight, root=None)
tree = GraphView(gc, directed=False, efilt=tree_map)
tree_edges = set()
# print('tree', tree)
for e in tree.edges():
u, v = map(int, e)
recovered_edges = extract_edges_from_pred(u, v, r2pred[u])
assert recovered_edges, 'empty!'
for i, j in recovered_edges:
tree_edges.add(((i, j)))
tree_nodes = list(set(itertools.chain(*tree_edges)))
vfilt = g.new_vertex_property('bool')
vfilt.set_value(False)
for n in tree_nodes:
vfilt[n] = True
efilt = g.new_edge_property('bool')
for i, j in tree_edges:
efilt[g.edge(i, j)] = 1
return GraphView(g, efilt=efilt, vfilt=vfilt)
def get_steiner_tree(g, root, obs_nodes, debug=False, verbose=False):
gc, eweight, r2pred = build_closure(g, obs_nodes,
debug=debug, verbose=verbose)
tree_map = min_spanning_tree(gc, eweight, root=None)
tree = GraphView(gc, directed=False, efilt=tree_map)
tree_edges = set()
for e in tree.edges():
u, v = map(int, e)
for i, j in extract_edges_from_pred(g, u, v, r2pred[u]):
tree_edges.add((j, i))
# a bit involved...
und_tree = edges_to_directed_tree(g, root, tree_edges)
return build_minimum_tree(g, root, obs_nodes, extract_edges(und_tree))
def get_steiner_tree(g, root, obs_nodes, debug=False, verbose=False):
gc, eweight, r2pred = build_closure(g,
obs_nodes,
debug=debug,
verbose=verbose)
tree_map = min_spanning_tree(gc, eweight, root=None)
tree = GraphView(gc, directed=False, efilt=tree_map)
tree_edges = set()
for e in tree.edges():
u, v = map(int, e)
for i, j in extract_edges_from_pred(g, u, v, r2pred[u]):
tree_edges.add((j, i))
# a bit involved...
und_tree = edges_to_directed_tree(g, root, tree_edges)
return build_minimum_tree(g, root, obs_nodes, extract_edges(und_tree))