84 lines
3.0 KiB
Python
84 lines
3.0 KiB
Python
import random
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from attributes import attributes
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class GA(attributes):
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# Inhert all the ga attributes from the attributes class.
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def __init__(self):
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super(GA, self).__init__()
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def evolve_generation(self, number_of_generations = 1, consider_termination = True):
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"""Evolves the ga the specified number of generations."""
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while(number_of_generations > 0 # Evolve the specified number of generations
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and (not consider_termination # and if consider_termination flag is set
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or self.termination_impl(self))): # then also check if termination conditions reached
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# If its the first generation then initialize the population
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if self.current_generation == 0:
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self.initialize_population()
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self.set_all_fitness()
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self.population.sort_by_best_fitness(self)
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# Otherwise evolve the population
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else:
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self.set_all_fitness()
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self.population.sort_by_best_fitness(self)
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self.parent_selection_impl(self)
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self.crossover_population_impl(self)
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self.survivor_selection_impl(self)
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self.mutation_population_impl(self)
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self.population.update()
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number_of_generations -= 1
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self.current_generation += 1
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def evolve(self):
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"""Runs the ga until the termination point has been satisfied."""
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while(self.active()):
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self.evolve_generation()
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def active(self):
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"""Returns if the ga should terminate based on the termination implimented."""
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return self.termination_impl(self)
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def initialize_population(self):
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"""Initialize the population using
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the initialization implimentation
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that is currently set.
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"""
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self.population = self.initialization_impl(self)
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def set_all_fitness(self):
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"""Will get and set the fitness of each chromosome in the population.
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If update_fitness is set then all fitness values are updated.
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Otherwise only fitness values set to None (i.e. uninitialized
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fitness values) are updated.
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"""
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# Check each chromosome
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for chromosome in self.population.get_chromosome_list():
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# Update fitness if needed or asked by the user
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if(chromosome.get_fitness() is None or self.update_fitness):
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chromosome.set_fitness(self.fitness_function_impl(chromosome))
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def sort_by_best_fitness(self, chromosome_set):
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"""Sorts the array by fitness.
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1st element has highest fitness.
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2nd element has second highest fitness.
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etc.
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"""
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return sorted(chromosome_set, # list to be sorted
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key = lambda chromosome: chromosome.get_fitness(), # by fitness
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reverse = True) # from highest to lowest fitness
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