def solve(self,
distance_matrix: np.ndarray,
max_time: float = 10.0,
start_cycle=None) -> Tuple[List[int], int]:
problem_solver = CandidateSteepSearch()
best_cycle: List[int] = problem_solver.solve(distance_matrix)
best_cost: int = utils.calculate_path_length(distance_matrix,
best_cycle)
local_search_invocation_count = 1
time_start: float = time.time()
duration = 0.0
while duration < max_time:
temp_cycle = self.__perturb(distance_matrix, best_cycle)
temp_cycle = problem_solver.solve(distance_matrix, temp_cycle)
local_search_invocation_count += 1
cost = utils.calculate_path_length(distance_matrix, temp_cycle)
if cost < best_cost:
best_cost = cost
best_cycle = temp_cycle
duration = time.time() - time_start
return best_cycle, local_search_invocation_count
def solve(self, distance_matrix: np.ndarray, max_time: float = 10.0, start_cycle=None) -> Tuple[List[int], int]:
problem_solver = CandidateSteepSearch()
random_problem_solver = RandomSearch()
# Generate random population
population: List[List[int]] = []
while len(population) < HybridEvolutionarySolver.POPULATION_SIZE:
solution = random_problem_solver.solve(distance_matrix)
if solution not in population:
population.append(solution)
population_costs = [utils.calculate_path_length(distance_matrix, solution) for solution in population]
local_search_invocation_count = 0
time_start: float = time.time()
duration = 0.0
while duration < max_time:
# Pick random parents
parent_1 = population[np.random.randint(HybridEvolutionarySolver.POPULATION_SIZE)]
parent_2 = parent_1
while parent_2 == parent_1:
parent_2 = population[np.random.randint(HybridEvolutionarySolver.POPULATION_SIZE)]
# Recombine
child = self.__recombine(parent_1, parent_2)
# Improve child with local search
child = problem_solver.solve(distance_matrix, child)
local_search_invocation_count += 1
# Ignore if child already in population
if child in population:
continue
# Search for worse solution than child
child_cost = utils.calculate_path_length(distance_matrix, child)
worst_cost = child_cost
worst_index = -1
for i, cost in enumerate(population_costs):
if cost > worst_cost:
worst_index = i
worst_cost = cost
# If no worse solution found then ignore child
if worst_index == -1:
continue
# Replace worse solution with child
population[worst_index] = child
population_costs[worst_index] = child_cost
duration = time.time() - time_start
best_index = np.argmin(population_costs)
return population[best_index], local_search_invocation_count
def solve(self,
distance_matrix: np.ndarray,
start_cycle=None) -> List[int]:
if self.gen_time == 0.0:
return RandomSearch.__generate_random_cycle(distance_matrix)
best_result_cycle = []
best_result_cycle_length = np.iinfo(distance_matrix.dtype).max
time_start = time.time()
while time.time() - time_start < self.gen_time:
result_cycle = RandomSearch.__generate_random_cycle(
distance_matrix)
result_cycle_length = utils.calculate_path_length(
distance_matrix, result_cycle)
if result_cycle_length < best_result_cycle_length:
best_result_cycle_length = result_cycle_length
best_result_cycle = result_cycle
return best_result_cycle
def __process_results(problem: StandardProblem,
result_title: str,
paths: list,
times: list,
search_invocations: list = None):
distance_matrix: np.ndarray = utils.create_distance_matrix(problem)
# Calculate min, max and average cycle lengths
cycle_lengths = [utils.calculate_path_length(distance_matrix, path) for path in paths]
minimum_length, shortest_cycle_index = min((val, idx) for (idx, val) in enumerate(cycle_lengths))
maximum_length = max(cycle_lengths)
average_length = round(sum(cycle_lengths) / len(cycle_lengths))
maximum_time = max(times)
minimum_time = min(times)
average_time = round(sum(times) / len(times), 3)
# Draw best cycle
shortest_path = [index + 1 for index in paths[shortest_cycle_index]]
result_title = f"{result_title}_{shortest_path[0]}"
utils.draw_graph(problem, shortest_path, result_title, minimum_length)
print(result_title)
print(f"Path : {shortest_path}")
print(f"Cycle length (min) : {minimum_length}")
print(f"Cycle length (max) : {maximum_length}")
print(f"Cycle length (avg) : {average_length}")
print(f"Time (min) : {round(minimum_time * 1000.0)}ms")
print(f"Time (max) : {round(maximum_time * 1000.0)}ms")
print(f"Time (avg) : {round(average_time * 1000.0)}ms")
if search_invocations:
maximum_invocations = max(search_invocations)
minimum_invocations = min(search_invocations)
average_invocations = round(sum(search_invocations) / len(search_invocations), 3)
print(f"Search invocations (min) : {minimum_invocations}")
print(f"Search invocations (max) : {maximum_invocations}")
print(f"Search invocations (avg) : {average_invocations}")
print()
return average_time
def _solve_single(distance_matrix: np.ndarray,
problem_solver: SearchProblemSolver):
cycle = problem_solver.solve(distance_matrix)
cost = utils.calculate_path_length(distance_matrix, cycle)
return cycle, cost
def global_convexity_tests(problem: StandardProblem,
number_of_solutions: int = 1000,
similarity_function=node_similarity,
title: str = ""):
distance_matrix = create_distance_matrix(problem)
problem_solver = GreedyLocalSearch(use_node_swap=True)
pool = Pool(processes=os.cpu_count())
pool_results = []
solutions = []
for i_ in range(number_of_solutions):
if len(pool_results) == os.cpu_count():
for pool_res in pool_results:
solution = pool_res.get()
solutions.append(np.array(solution))
pool_results.clear()
res = pool.apply_async(problem_solver.solve, (distance_matrix, ))
pool_results.append(res)
for pool_res in pool_results:
solution = pool_res.get()
solutions.append(np.array(solution))
pool_results.clear()
pool.close()
solution_cost = np.array([
calculate_path_length(distance_matrix, list(cycle))
for cycle in solutions
])
best_cost_index = np.argmin(solution_cost)
best_solution = solutions[best_cost_index]
similarity = \
np.array([similarity_function(cycle, best_solution) for cycle in solutions])
average_other_similarity = np.zeros(shape=similarity.shape)
best_solution_similarity = np.zeros(shape=similarity.shape)
for i in np.arange(start=0, stop=similarity.shape[0]):
mask = np.ones(similarity.shape, bool)
mask[i] = False
average_other_similarity[i] = np.average(similarity[mask])
best_solution_similarity[i] = similarity_function(
solutions[i], best_solution)
correlation = np.corrcoef(solution_cost, average_other_similarity)[0][1]
print(f"Correlation parameter ({title}) : {correlation}")
indices = np.argsort(solution_cost)
plt.scatter(solution_cost[indices],
average_other_similarity[indices],
label="Average other similarity")
plt.scatter(solution_cost[indices],
best_solution_similarity[indices],
label="Best solution similarity")
plt.legend()
plt.title(title)
plt.savefig(f"./graphs/{title}.pdf")
plt.show()