GeneticAlgorithm.java

package org.school.schedule;

import java.util.ArrayList;
import java.util.stream.IntStream;

public class GeneticAlgorithm {
	private Data data;

	public GeneticAlgorithm(Data data) {
		this.data = data;
	}
	public Population evolve(Population population) {
		return mutatePopulation(crossoverPopulation(population));
	}
	
	Population crossoverPopulation(Population population) {
		Population crossoverPopulation = new Population(population.getSchedules().size(), data);
		IntStream.range(0, Driver.NUMB_OF_ELITE_SCHEDULES).forEach(x -> crossoverPopulation.getSchedules().set(x, population.getSchedules().get(x)));
		IntStream.range(Driver.NUMB_OF_ELITE_SCHEDULES, population.getSchedules().size()).forEach(x -> {
			if (Driver.CROSSOVER_RATE > Math.random()) {
				Schedule schedule1 = selectTournamentPopulation(population).sortByFitness().getSchedules().get(0);
				Schedule schedule2 = selectTournamentPopulation(population).sortByFitness().getSchedules().get(0);
				crossoverPopulation.getSchedules().set(x, crossoverSchedule(schedule1, schedule2));
			} else {
				crossoverPopulation.getSchedules().set(x, population.getSchedules().get(x));
			}
		});

		return crossoverPopulation;
	}
	
	Schedule crossoverSchedule(Schedule schedule1, Schedule schedule2) {
		Schedule crossoverSchedule = new Schedule(data).initialize();
		IntStream.range(0, crossoverSchedule.getClasses().size()).forEach(x -> {
			if (Math.random() > 0.5) crossoverSchedule.getClasses().set(x, schedule1.getClasses().get(x));
			else crossoverSchedule.getClasses().set(x, schedule2.getClasses().get(x));
		});
		return crossoverSchedule;
	}
	
	Schedule mutateSchedule(Schedule mutateSchedule) {
		Schedule schedule = new Schedule(data).initialize();
		IntStream.range(0, mutateSchedule.getClasses().size()).forEach(x -> {
			if (Driver.MUTATION_RATE > Math.random()) mutateSchedule.getClasses().set(x, schedule.getClasses().get(x));
		});
		return mutateSchedule;
	}
	
	Population mutatePopulation(Population population) {
		Population mutatePopulation = new Population(population.getSchedules().size(), data);
		ArrayList<Schedule> schedules = mutatePopulation.getSchedules();
		IntStream.range(0, Driver.NUMB_OF_ELITE_SCHEDULES).forEach(x -> schedules.set(x, population.getSchedules().get(x)));
		IntStream.range(Driver.NUMB_OF_ELITE_SCHEDULES, population.getSchedules().size()).forEach(x -> {
			schedules.set(x, mutateSchedule(population.getSchedules().get(x)));
		});
		return mutatePopulation;
	}
	
	Population selectTournamentPopulation(Population population) {
		Population tournamentPopulation = new Population(Driver.TOURNAMENT_SELECTION_SIZE, data);
		IntStream.range(0, Driver.TOURNAMENT_SELECTION_SIZE).forEach(x -> {
			tournamentPopulation.getSchedules().set(x, population.getSchedules().get((int)(Math.random() *  population.getSchedules().size())));
		});
		return tournamentPopulation;
	}
}