cgp.py 文件源码

def point_mutation(individual, random_state=None):
    """
    Randomly pick a gene in individual and mutate it.
    The mutation is either rewiring, i.e. changing the inputs, or changing the operator (head of gene)
    :param individual: instance of Base
    :type individual: instance of Cartesian
    :param random_state: an instance of np.random.RandomState, a seed integer or None
    :return: new instance of Base
    """
    random_state = check_random_state(random_state)
    n_terminals = len(individual.pset.terminals)
    i = random_state.randint(n_terminals, len(individual) - 1)
    el, c, r, l = individual.mapping[i]
    gene = l[r]
    if isinstance(gene, list):
        new_gene = gene[:]
        j = random_state.randint(0, len(gene))
        if j == 0:  # function
            new_j = individual.pset.imapping[random_state.choice(individual.pset.operators)]
        else:       # input
            new_j = random_state.choice(individual._valid_inputs[i])
        new_gene[j] = new_j

    else: # output gene
        new_gene = random_state.randint(0, len(individual) - individual.n_out - 1)
    new_individual = copy.copy(individual)
    new_individual[i] = new_gene
    return new_individual