evolution.py

import numpy as np
import random


def mutate_reverse(chromosome, start_index, length):
    if start_index <= 0:
        start_index = 1

    sub_chromosome = list(reversed(chromosome[start_index:(start_index + length)]))
    chromosome[start_index:(start_index + length)] = sub_chromosome
    return chromosome


def mutate_switch_cities(chromosome, index_first, index_second):
    if index_first <= 0:
        index_first = 1

    if index_second <= 0:
        index_second = 0

    chromosome[index_second], chromosome[index_first] = chromosome[index_first], chromosome[index_second]
    return chromosome


def one_point_pmx_crossover(parent_one, parent_two):
    """
    Function witch use PMX crossover for TSP
    :param parent_one:  chromosome object
    :param parent_two:  chromosome object
    :return:    two offsprings
    """
    crossover_point = random.randint(2, len(parent_one.get_cities_list()))
    parent_one_temp = np.array(parent_one.get_cities_list())
    parent_two_temp = np.array(parent_two.get_cities_list())

    # We start from index no 1 because city with no 0 should be always at the beginning
    offspring_one = [parent_one.get_cities_list()[0]]  # Zero at the beginning
    for idx in range(1, crossover_point - 1):
        value = parent_two.get_cities_list()[idx]
        parent_one_temp[np.where(parent_one_temp == value)], parent_one_temp[idx] \
            = parent_one_temp[idx], parent_one_temp[np.where(parent_one_temp == value)]
        offspring_one = np.append(offspring_one, parent_one_temp[idx])
    offspring_one = np.concatenate((offspring_one, parent_one_temp[(crossover_point - 1):]))

    offspring_two = [parent_two.get_cities_list()[0]]  # Zero at the beginning
    for idx in range(1, crossover_point - 1):
        value = parent_one.get_cities_list()[idx]
        parent_two_temp[np.where(parent_two_temp == value)], parent_two_temp[idx] \
            = parent_two_temp[idx], parent_two_temp[np.where(parent_two_temp == value)]
        offspring_two = np.append(offspring_two, parent_two_temp[idx])
    offspring_two = np.concatenate((offspring_two, parent_two_temp[(crossover_point - 1):]))

    return offspring_one, offspring_two