def merge_double_bridge(xy, best_order, start_point):
original_length = len(best_order)
trial_order = double_bridge.perturbed_climb(xy, best_order, 1)
trial_length = basic.tour_length(xy, trial_order)
print("trial tour length: " + str(trial_length))
old_edges, new_edges = tour_diff(best_order, trial_order)
basic.write_edges(old_edges, "output/old_edges_test.txt")
basic.write_edges(new_edges, "output/new_edges_test.txt")
best_order = merge(xy, best_order, trial_order)
new_length = basic.tour_length(xy, best_order)
print("new length: " + str(new_length))
assert (trial_length >= new_length)
assert (len(best_order) == original_length)
return best_order
def perturbed_climb(xy, order, iterations):
best_order = order[:]
best_length = basic.tour_length(xy, best_order)
climber = TwoOpt(xy)
climber.tour.reset(best_order)
for i in range(iterations):
climber.tour.double_bridge_perturbation()
climber.optimize()
new_length = climber.tour.tour_length()
if new_length < best_length:
best_order = climber.tour.node_ids
best_length = new_length
else:
climber.tour.reset(best_order)
return climber.tour.node_ids
def perturbed_hill_climb(xy, tour):
tries = 0
success = 0
best_length = tour_util.length(xy, tour)
while True:
new_tour, naive_new_length = two_opt.optimize(xy, tour_util.double_bridge(tour)) # double bridge
#test_tour = tour[:]
#random.shuffle(test_tour)
#new_tour, naive_new_length = two_opt.optimize(xy, test_tour) # random restart
segments = Splitter(tour, new_tour).get_segments()
kmoves = segments_to_beneficial_kmoves(xy, segments, tour)
max_gain = 0
if kmoves:
max_gain = sum([k[0] for k in kmoves])
naive_gain = best_length - naive_new_length
# There may be cases where naive gain is more than decomposed gains:
# decomposed gains currently only return moves that can be independently performed.
# Infeasible moves that are improvements but only can be combined with other moves to become feasible
# (a potentially computationally expensive search) wil be excluded from the decomposed moves.
dd_gain = 0 # gain due to decomposed kmoves.
if kmoves:
for k in kmoves:
print(' trying {}-opt move with gain {}'.format(len(k[1]['adds']), k[0]))
test_tour = perform_kmove(tour, k[1])
if len(test_tour) == len(tour):
tour = test_tour
best_length -= k[0]
dd_gain += k[0]
if naive_gain > dd_gain:
print('naive_gain ({}) greater than dd_gain ({})'.format(naive_gain, dd_gain))
tour = new_tour
best_length = naive_new_length
if naive_gain > 0 or dd_gain > 0:
success += 1
if dd_gain > 0 and dd_gain > naive_gain:
print(' dd gain {} greater than naive gain {}'.format(dd_gain, naive_gain))
tries += 1
current_length = basic.tour_length(xy, tour)
assert(best_length == current_length)
if current_length <= TARGET_LENGTH:
break
print('current best: {} (iteration {}), improvement rate: {}'.format(best_length, tries, success / tries))
def perturbed_hill_climb_naive(xy, tour):
tries = 0
success = 0
best_length = tour_util.length(xy, tour)
while True:
new_tour, naive_new_length = two_opt.optimize(xy, tour_util.double_bridge(tour)) # double bridge
#test_tour = tour[:]
#random.shuffle(test_tour)
#new_tour, naive_new_length = two_opt.optimize(xy, test_tour) # random restart
naive_gain = best_length - naive_new_length
if naive_gain > 0:
tour = new_tour
best_length = naive_new_length
success += 1
tries += 1
current_length = basic.tour_length(xy, tour)
assert(best_length == current_length)
if current_length <= TARGET_LENGTH:
break
print('current best: {} (iteration {}), improvement rate: {}'.format(best_length, tries, success / tries))
basic.write_edges(old_edges, "output/old_edges_test.txt")
basic.write_edges(new_edges, "output/new_edges_test.txt")
best_order = merge(xy, best_order, trial_order)
new_length = basic.tour_length(xy, best_order)
print("new length: " + str(new_length))
assert (trial_length >= new_length)
assert (len(best_order) == original_length)
return best_order
if __name__ == "__main__":
xy = reader.read_xy("../data/xqf131.tsp")
order = [i for i in range(len(xy))]
random.shuffle(order)
order = opt2(order)
print("initial tour length: " + str(basic.tour_length(xy, order)))
for i in range(1000):
basic.write_edges_from_order(order, "output/order_test.txt")
print("merge iteration: " + str(i))
premerge_length = basic.tour_length(xy, order)
#order = merge_nn(xy, order, i)
order = merge_double_bridge(xy, order, i)
postmerge_length = basic.tour_length(xy, order)
if postmerge_length != premerge_length:
order = opt2(order)
postmerge_climb_length = basic.tour_length(xy, order)
if postmerge_climb_length != postmerge_length:
print("post-merge hill climb: " + str(postmerge_climb_length))
def tour_length(self):
return basic.tour_length(self.xy, self.node_ids)