def run(self):
""" runs the bionomic algorithm
The steps for the bionomic algorithm are corresponding to section 5.10 from Pinol & Beasley (2006).
1. An initial population is created
2. Each individual from the initial population is locally improved
repeating:
3. Generation of parent sets
4. Generation of children sets incl. removal of duplicates
5. Local improvement of every children
6. Insertion into population of best child and removing of worst individual in population
until termination
The algorithm terminates once 40,000 children have been created
:return: the phenotyoe of the best solution
"""
monitor = Monitor(self.alp.nr_planes, self.alp.nr_runways,
self.alp._objective)
nr_children_limit = 50000 # termination criterion:
nr_children_current = 0 # counter
iter_without_children = 0 # subsequent iterations with duplicates only
population = Population(alp=self.alp, size=100)
winners = [] # set of inserted children
iteration = 0 # iteration counter
start_time = time.time()
while nr_children_current < nr_children_limit and iter_without_children < 10:
monitor.evaluate_population(population.members,
time.time() - start_time)
iteration += 1
print('- ' * 10)
print('[ STATUS ] Iteration %d / Children: %d' %
(iteration, nr_children_current))
parent_sets, theta = population.generate_parent_sets()
monitor.evaluate_parent_sets(parent_sets, theta,
population._graph.number_of_edges())
children = population.generate_children(parent_sets)
if len(children) > 0:
monitor.evaluate_children(children)
monitor.evaluate_parents(max(children)._parents)
winner = population.insert_children(children)
winners.append(winner)
monitor.evaluate_winner(winners)
nr_children_current += len(children)
iter_without_children = 0
else:
iter_without_children += 1
monitor.write_row()
return population.members.pop().phenotype
def solve(self):
"""
Population management and solving structure of the genetic heuristic.
Includes:
1) Initialization of population
2) Initialization of weights
3) Weight adjustment
4) Crossover (w. Parent selection)
5) Diversification
After the set stoppage criterion is met the solution variable will be allocated
"""
global HAMMING_DISTANCE_MATRIX
# 0) LOCAL SAVE STATIC PARAMETERS
target_proportion = self.target_proportion
nr_customers = self.vrp_data.nr_customers
max_size = self.population_size + self.min_sub_pop_size
iter_penalty_adjust = self.iter_penalty_adjust
avg_demand = sum([customer for customer in self.vrp_data.customers
]) / nr_customers
diversification_size = math.floor(self.min_sub_pop_size / 3)
# 1) initialize the first population and set population specific parameters
population = self.random_population_initialization()
list_feas_quantity = [False] * iter_penalty_adjust
list_feas_distance = [False] * iter_penalty_adjust
inf_pop_size = len(population["infeasible"])
feas_pop_size = len(population["feasible"])
# 2) initialize weights
# get average distance between customers (length of solution / nr_customers)
# we must add 1 as the distance from and to the depot is also considered c+1 arcs
avg_distance_customers = get_average_solution_length(population)
self.w_penalty_load = avg_distance_customers / avg_demand
# 3) Do calculations
try:
best_instance = get_minimum_length_instance(population["feasible"])
best_instance_length = best_instance.length
except AttributeError:
best_instance = None
best_instance_length = np.inf # infinite -> no valid solution found so far
GENERAL_LOGGER.warning(
"No feasible solution in the initial solution set")
# initialize stoppage criteria
max_iter_wo_improvement, iter_without_impr, iter_wa = self.max_iter_wo_improvement, 0, 0
max_time, start_t = self.max_time, time()
monitor = Monitor("MDVRP" + str(self.vrp_data.nr_customers))
while time(
) - start_t < max_time and iter_without_impr < max_iter_wo_improvement:
# 3.1) PARENT SELECTION
parent_1 = self.parent_selection(population)
parent_2 = self.parent_selection(population)
monitor.evaluate_parents(parent_1, parent_2)
# 3.2) CROSSOVER (PIX)
offspring = self.crossover(parent_1, parent_2)
monitor.evaluate_offspring(offspring)
# 3.3) EDUCATION
length_pen_factor = self.w_penalty_duration
load_pen_factor = self.w_penalty_load
monitor.evaluate_penaly_factors(length_pen_factor, load_pen_factor)
all_offsprings = [offspring]
if random.random() <= self.education_probability:
offspring.route_improvement(load_pen_factor, length_pen_factor)
offspring.pattern_improvement()
offspring.route_improvement(load_pen_factor, length_pen_factor)
if not offspring.feasibility and random.random(
) <= self.repair_probability:
repair_offspring = copy.deepcopy(offspring)
for x in range(1, 3):
length_pen_factor *= 10
load_pen_factor *= 10
repair_offspring.route_improvement(
load_pen_factor, length_pen_factor)
repair_offspring.pattern_improvement()
repair_offspring.route_improvement(
load_pen_factor, length_pen_factor)
repair_offspring.evaluate_solution()
if repair_offspring.feasibility:
all_offsprings.append(repair_offspring)
continue
monitor.evaluate_offspring_after_education(all_offsprings[0])
for offspring in all_offsprings:
list_feas_quantity[iter_wa] = (offspring.penalty_duration == 0)
list_feas_distance[iter_wa] = (offspring.penalty_load == 0)
monitor.evaluate_feasibility(list_feas_quantity,
list_feas_distance)
# 3.4) APPEND HEMMING DISTANCE
merged_population = merge_population(population)
hamming_distance_matrix = extend_hamming_distance_matrix(
merged_population, offspring)
monitor.evaluate_entropy(hamming_distance_matrix)
# for offspring in all_offspring:
if offspring.feasibility:
# FEASIBLE OFFSPRING HANDLING
feas_pop_size += 1
population["feasible"].append(offspring)
# check if we need to perform survivor selection
if feas_pop_size > max_size:
POPULATON_LOGGER.debug("feasible_survivor_selection")
feas_pop_size = self.min_sub_pop_size
self.survivor_selection(population, "feasible",
self.min_sub_pop_size)
# check if we improved the best solution
if best_instance_length > offspring.length:
best_instance = offspring
best_instance_length = offspring.length
GENERAL_LOGGER.info(best_instance_length)
iter_without_impr = 0
else:
iter_without_impr += 1
else:
# INFEASIBLE OFFSPRING HANDLING
inf_pop_size += 1
population["infeasible"].append(offspring)
# check if we need to perform survivor selection
if inf_pop_size > max_size:
POPULATON_LOGGER.debug("infeasible_survivor_selection")
inf_pop_size += self.min_sub_pop_size
self.survivor_selection(population, "infeasible",
self.min_sub_pop_size)
iter_without_impr += 1
# 3.4) WEIGHT ADJUSTMENTS EVERY iter_wa ITERATIONS
if iter_wa == (iter_penalty_adjust - 1):
iter_wa = 0
feasibility_proportion_quantity = sum(
list_feas_quantity) / iter_penalty_adjust
feasibility_proportion_distance = sum(
list_feas_distance) / iter_penalty_adjust
if feasibility_proportion_quantity <= target_proportion - 0.05:
self.w_penalty_load = self.w_penalty_load * 1.2
elif feasibility_proportion_quantity >= target_proportion - 0.05:
self.w_penalty_load = self.w_penalty_load * 0.85
if feasibility_proportion_distance <= target_proportion - 0.05:
self.w_penalty_duration = self.w_penalty_duration * 1.2
elif feasibility_proportion_distance >= target_proportion - 0.05:
self.w_penalty_duration = self.w_penalty_duration * 0.85
else:
iter_wa += 1
# 3.5) DIVERSIFICATION
if iter_without_impr > 0 and (iter_without_impr %
self.iter_diversification) == 0:
GENERAL_LOGGER.info("diversification")
# the length of both population subsets will be reduced
feas_pop_size, inf_pop_size = diversification_size, diversification_size
# we diversify if the iterations without improvement is a true dividor of the target
population = self.survivor_selection(
population, "feasible", diversification_size)
population = self.survivor_selection(
population, "infeasible", diversification_size)
# perform random fill
population = self._random_fill_population(population)
monitor.evaluation_population(population['feasible'],
population['infeasible'],
time() - start_t)
monitor.evaluate_best(best_instance)
monitor.write_row()
self.solution = best_instance