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45 lines (40 loc) · 2.29 KB
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import numpy
def cal_pop_fitness(equation_inputs, pop):
# Calculating the fitness value of each solution in the current population.
# The fitness function calulates the sum of products between each input and its corresponding weight.
fitness = numpy.sum(pop*equation_inputs, axis=1)
return fitness
def select_mating_pool(pop, fitness, num_parents):
# Selecting the best individuals in the current generation as parents for producing the offspring of the next generation.
parents = numpy.empty((num_parents, pop.shape[1]))
for parent_num in range(num_parents):
max_fitness_idx = numpy.where(fitness == numpy.max(fitness))
max_fitness_idx = max_fitness_idx[0][0]
parents[parent_num, :] = pop[max_fitness_idx, :]
fitness[max_fitness_idx] = -99999999999
return parents
def crossover(parents, offspring_size):
offspring = numpy.empty(offspring_size)
# The point at which crossover takes place between two parents. Usually, it is at the center.
crossover_point = numpy.uint8(offspring_size[1]/2)
for k in range(offspring_size[0]):
# Index of the first parent to mate.
parent1_idx = k%parents.shape[0]
# Index of the second parent to mate.
parent2_idx = (k+1)%parents.shape[0]
# The new offspring will have its first half of its genes taken from the first parent.
offspring[k, 0:crossover_point] = parents[parent1_idx, 0:crossover_point]
# The new offspring will have its second half of its genes taken from the second parent.
offspring[k, crossover_point:] = parents[parent2_idx, crossover_point:]
return offspring
def mutation(offspring_crossover, num_mutations=1):
mutations_counter = numpy.uint8(offspring_crossover.shape[1] / num_mutations)
# Mutation changes a number of genes as defined by the num_mutations argument. The changes are random.
for idx in range(offspring_crossover.shape[0]):
gene_idx = mutations_counter - 1
for mutation_num in range(num_mutations):
# The random value to be added to the gene.
random_value = numpy.random.uniform(-1.0, 1.0, 1)
offspring_crossover[idx, gene_idx] = offspring_crossover[idx, gene_idx] + random_value
gene_idx = gene_idx + mutations_counter
return offspring_crossover