def move_around_face(grid, vertices, visual_params):
"""
Move around the vertices of the given face in order, by continuously moving across darts connecting consecutive
vertices.
:param grid: Grid graph to compute MSSP
:param vertices: face vertices given in order
:return: All the shortest path distances for each vertex in the vertices list.
"""
# Ensure there is at least one vertex when computing SSSP for each vertex in vertices.
assert (len(vertices) > 1)
s1 = vertices[0] # first source vertex
holy_tree = fast_initial_tree(grid, grid.genus, s1)
print("---Initial tree---\n{}".format(holy_tree))
print(holy_tree.is_holy_tree(grid, "Root {}".format(s1)))
print("----------------------")
for i in range(len(vertices)):
s1 = vertices[i]
s2 = vertices[(i + 1) % len(vertices)]
# Source will move from s1 -> s2, updating pred and dist dictionaries.
move_across_dart(grid, s1, s2, holy_tree, visual_params)
# For sanity check, at the end of the cycle, holy tree should be exactly same as the initial holy tree.
initial_holy_tree = fast_initial_tree(grid, grid.genus, vertices[0])
assert initial_holy_tree == holy_tree, holy_tree.report_difference(initial_holy_tree)
def test_holy_tree(self):
g1 = grid.g1()
# Source vertex.
vertex = g1.get_vertex((1, 1))
fast_holy_tree = initial_holy_tree.fast_initial_tree(g1, vertex)
slow_holy_tree = initial_holy_tree.bellman_ford_initial_tree(g1, vertex)
self.assertEqual(fast_holy_tree, slow_holy_tree)
def test_initial_tree_g2(self):
# NOTE(lkhamsurenl): Following line is needed if copying graph is too deep, when using copy.deepcopy
sys.setrecursionlimit(10000)
grid2 = Grid(2, 6, 6)
# Source vertex.
vertex = grid2.get_vertex((1, 1))
fast_start = time.time()
fast_holy_tree = initial_holy_tree.fast_initial_tree(grid2, vertex)
fast_end = time.time()
slow_holy_tree = initial_holy_tree.bellman_ford_initial_tree(grid2, vertex)
slow_end = time.time()
print("g = 2 \n fast: {}, slow: {}".format(fast_end - fast_start, slow_end - fast_end))
self.assertEqual(fast_holy_tree, slow_holy_tree)
def move_across_dart(grid, s1, s2, holy_tree, visual_params):
"""
Move across dart s1 -> s2, changing holy_tree through series of pivots.
:param grid:
:param holy_tree: Holy tree rooted at s1.
:param s1: Source vertex.
:param s2: Destination vertex.
:param visual_params: (vertex_mapping, face_mapping, primal_pdf, dual_pdf).
:return:
"""
# Original value of the edge s1 -> s2.
dart = copy.deepcopy(s1.neighbors[s2])
# Distance from s to s1.
lambda_weight = Weight(homology=[0 for _ in range(2 * grid.genus)])
s = grid.add_vertex((-1, -1)) # special vertex to walk along the s1 -> s2.
holy_tree.dist[s] = Weight(homology=[0 for _ in range(2 * grid.genus)])
Dart(s, s1, Weight(0, [0 for _ in range(2 * grid.genus)], 0), dart.right, dart.left)
Dart(s, s2, copy.deepcopy(dart.weight), dart.left, dart.right)
# Remove edge between s1, s2.
__remove_edge__(s1, s2)
# Fix pred pointers.
holy_tree.pred[s] = None
holy_tree.pred[s1] = s
holy_tree.pred[s2] = s
# Set dist to s2.
holy_tree.dist[s2] = s.neighbors[s2].weight
# Reduce distance to both s1 and s2 form s by same value: Weight(0, -homology, -leafmost)
Dart(s, s1, Weight(0, [-h for h in dart.weight.homology], -dart.weight.leafmost), dart.right, dart.left)
holy_tree.add_subtree(s1, Weight(0, [-h for h in dart.weight.homology], -dart.weight.leafmost))
Dart(s, s2, Weight(1, [0 for _ in range(2 * grid.genus)], 0), dart.left, dart.right)
holy_tree.add_subtree(s2, Weight(0, [-h for h in dart.weight.homology], -dart.weight.leafmost))
while True:
# Get all the active darts.
active = {}
(blue, red) = __active_darts__(s1, s2, holy_tree.pred)
for u in grid.vertices:
for v in u.neighbors:
if u.name in blue and v.name in red:
active[u.neighbors[v]] = holy_tree.dist[u] + u.neighbors[v].weight - holy_tree.dist[v]
# Do pivot on dart with minimum slack.
minimum_slack = Weight(length=float('inf'))
min_dart = None
for d in active.keys():
if minimum_slack > active[d]:
min_dart = d
minimum_slack = active[d]
# Check the value of the min_slack / 2 would not result in s "go over" s2.
if min_dart is not None and Weight(float(minimum_slack.length) / 2,
[float(i) / 2 for i in minimum_slack.homology],
float(minimum_slack.leafmost) / 2) + lambda_weight <= \
Weight(1, [0 for _ in range(2 * grid.genus)], 0):
# Get darts that are pivoting in and pivoting out.
pivot_in = min_dart
pivot_out = holy_tree.pivot_out(pivot_in)
# Draw primal and dual graphs for visualization.
draw_primal(grid, (s1.name,s2.name), blue, red, holy_tree.pred, visual_params[0], pivot_in, pivot_out,
visual_params[2])
# In dual graph, dual of the reverse of the pivot_out will pivot in.
draw_dual(grid, blue, red, holy_tree.pred, visual_params[1], pivot_out.reverse, pivot_in, visual_params[3])
# w represents the value to move s from s1 to s2.
w = Weight(float(minimum_slack.length) / 2, [float(i) / 2 for i in minimum_slack.homology],
float(minimum_slack.leafmost) / 2)
lambda_weight += w # Keep track of the current progress.
if holy_tree.pred[s1] == s:
s.neighbors[s1].weight += w
holy_tree.add_subtree(s1, w)
if holy_tree.pred[s2] == s:
s.neighbors[s2].weight -= w
holy_tree.add_subtree(s2, -w)
# Update dist and pred pointers respectively for the vertices.
holy_tree.pred[min_dart.head] = min_dart.tail
# here, if we check the values, it should still be the holy tree
print("-------------------------------")
print(holy_tree.is_holy_tree(grid, "Pivot: {}, slack: {}".format(min_dart, minimum_slack)))
else: # no more pivot, move the values dart.weight - lambda_weight, then make the s2 new pivot
draw_primal(grid, (s1.name,s2.name), blue, red, holy_tree.pred, visual_params[0], None, None,
visual_params[2])
draw_dual(grid, blue, red, holy_tree.pred, visual_params[1], None, None, visual_params[3])
delta = Weight(1, [0 for _ in range(2 * grid.genus)], 0) - lambda_weight
holy_tree.add_subtree(s2, -delta)
print("When moved all the way to {0}, distance to {0}: {1}".format(s2, holy_tree.dist[s2]))
holy_tree.add_subtree(s1, delta)
print("When moved all the way to {0}, distance to {1}: {2}, dart: {3}".format(s2, s1, holy_tree.dist[s1],
dart.weight))
break
# Remove s.
grid.remove_vertex(s.name)
del holy_tree.pred[s]
del holy_tree.dist[s]
# Insert back the edge between s1 and s2.
src.model.edge.Edge(s1, s2, copy.deepcopy(dart.weight), dart.left, dart.right)
# s2 is the new root.
holy_tree.pred[s2] = None
holy_tree.pred[s1] = s2
# Ensure that there is no tense dart at the end of the root move.
print(holy_tree.is_holy_tree(grid, "Root {}".format(s2)))
# Compute correct holy tree rooted at s2, ensure it is equal to the current holy tree.
correct_holy_tree = fast_initial_tree(grid, grid.genus, s2)
assert correct_holy_tree == holy_tree, holy_tree.report_difference(correct_holy_tree)
print("done with {0} -> {1}. New root is {1}".format(s1, s2))
