/** * Evolves the population of chromosomes within a genotype. This will execute all of the genetic * operators added to the present active configuration and then invoke the natural selector to * choose which chromosomes will be included in the next generation population. * * @param a_pop the population to evolve * @param a_conf the configuration to use for evolution * @return evolved population * @author Klaus Meffert * @since 3.2 */ public Population evolve(Population a_pop, Configuration a_conf) { Population pop = a_pop; int originalPopSize = a_conf.getPopulationSize(); boolean monitorActive = a_conf.getMonitor() != null; IChromosome fittest = null; // If first generation: Set age to one to allow genetic operations, // see CrossoverOperator for an illustration. // ---------------------------------------------------------------- if (a_conf.getGenerationNr() == 0) { int size = pop.size(); for (int i = 0; i < size; i++) { IChromosome chrom = pop.getChromosome(i); chrom.increaseAge(); } } else { // Select fittest chromosome in case it should be preserved and we are // not in the very first generation. // ------------------------------------------------------------------- if (a_conf.isPreserveFittestIndividual()) { /** @todo utilize jobs. In pop do also utilize jobs, especially for fitness computation */ fittest = pop.determineFittestChromosome(0, pop.size() - 1); } } if (a_conf.getGenerationNr() > 0) { // Adjust population size to configured size (if wanted). // Theoretically, this should be done at the end of this method. // But for optimization issues it is not. If it is the last call to // evolve() then the resulting population possibly contains more // chromosomes than the wanted number. But this is no bad thing as // more alternatives mean better chances having a fit candidate. // If it is not the last call to evolve() then the next call will // ensure the correct population size by calling keepPopSizeConstant. // ------------------------------------------------------------------ keepPopSizeConstant(pop, a_conf); } // Ensure fitness value of all chromosomes is udpated. // --------------------------------------------------- if (monitorActive) { // Monitor that fitness value of chromosomes is being updated. // ----------------------------------------------------------- a_conf .getMonitor() .event( IEvolutionMonitor.MONITOR_EVENT_BEFORE_UPDATE_CHROMOSOMES1, a_conf.getGenerationNr(), new Object[] {pop}); } updateChromosomes(pop, a_conf); if (monitorActive) { // Monitor that fitness value of chromosomes is being updated. // ----------------------------------------------------------- a_conf .getMonitor() .event( IEvolutionMonitor.MONITOR_EVENT_AFTER_UPDATE_CHROMOSOMES1, a_conf.getGenerationNr(), new Object[] {pop}); } // Apply certain NaturalSelectors before GeneticOperators will be executed. // ------------------------------------------------------------------------ pop = applyNaturalSelectors(a_conf, pop, true); // Execute all of the Genetic Operators. // ------------------------------------- applyGeneticOperators(a_conf, pop); // Reset fitness value of genetically operated chromosomes. // Normally, this should not be necessary as the Chromosome class // initializes each newly created chromosome with // FitnessFunction.NO_FITNESS_VALUE. But who knows which Chromosome // implementation is used... // ---------------------------------------------------------------- int currentPopSize = pop.size(); for (int i = originalPopSize; i < currentPopSize; i++) { IChromosome chrom = pop.getChromosome(i); chrom.setFitnessValueDirectly(FitnessFunction.NO_FITNESS_VALUE); // Mark chromosome as new-born. // ---------------------------- chrom.resetAge(); // Mark chromosome as being operated on. // ------------------------------------- chrom.increaseOperatedOn(); } // Increase age of all chromosomes which are not modified by genetic // operations. // ----------------------------------------------------------------- int size = Math.min(originalPopSize, currentPopSize); for (int i = 0; i < size; i++) { IChromosome chrom = pop.getChromosome(i); chrom.increaseAge(); // Mark chromosome as not being operated on. // ----------------------------------------- chrom.resetOperatedOn(); } // If a bulk fitness function has been provided, call it. // ------------------------------------------------------ BulkFitnessFunction bulkFunction = a_conf.getBulkFitnessFunction(); if (bulkFunction != null) { if (monitorActive) { // Monitor that bulk fitness will be called for evaluation. // -------------------------------------------------------- a_conf .getMonitor() .event( IEvolutionMonitor.MONITOR_EVENT_BEFORE_BULK_EVAL, a_conf.getGenerationNr(), new Object[] {bulkFunction, pop}); } /** @todo utilize jobs: bulk fitness function is not so important for a prototype! */ bulkFunction.evaluate(pop); if (monitorActive) { // Monitor that bulk fitness has been called for evaluation. // --------------------------------------------------------- a_conf .getMonitor() .event( IEvolutionMonitor.MONITOR_EVENT_AFTER_BULK_EVAL, a_conf.getGenerationNr(), new Object[] {bulkFunction, pop}); } } // Ensure fitness value of all chromosomes is udpated. // --------------------------------------------------- if (monitorActive) { // Monitor that fitness value of chromosomes is being updated. // ----------------------------------------------------------- a_conf .getMonitor() .event( IEvolutionMonitor.MONITOR_EVENT_BEFORE_UPDATE_CHROMOSOMES2, a_conf.getGenerationNr(), new Object[] {pop}); } updateChromosomes(pop, a_conf); if (monitorActive) { // Monitor that fitness value of chromosomes is being updated. // ----------------------------------------------------------- a_conf .getMonitor() .event( IEvolutionMonitor.MONITOR_EVENT_AFTER_UPDATE_CHROMOSOMES2, a_conf.getGenerationNr(), new Object[] {pop}); } // Apply certain NaturalSelectors after GeneticOperators have been applied. // ------------------------------------------------------------------------ pop = applyNaturalSelectors(a_conf, pop, false); // Fill up population randomly if size dropped below specified percentage // of original size. // ---------------------------------------------------------------------- if (a_conf.getMinimumPopSizePercent() > 0) { int sizeWanted = a_conf.getPopulationSize(); int popSize; int minSize = (int) Math.round(sizeWanted * (double) a_conf.getMinimumPopSizePercent() / 100); popSize = pop.size(); if (popSize < minSize) { IChromosome newChrom; IChromosome sampleChrom = a_conf.getSampleChromosome(); Class sampleChromClass = sampleChrom.getClass(); IInitializer chromIniter = a_conf.getJGAPFactory().getInitializerFor(sampleChrom, sampleChromClass); while (pop.size() < minSize) { try { /** * @todo utilize jobs as initialization may be time-consuming as invalid combinations * may have to be filtered out */ newChrom = (IChromosome) chromIniter.perform(sampleChrom, sampleChromClass, null); if (monitorActive) { // Monitor that fitness value of chromosomes is being updated. // ----------------------------------------------------------- a_conf .getMonitor() .event( IEvolutionMonitor.MONITOR_EVENT_BEFORE_ADD_CHROMOSOME, a_conf.getGenerationNr(), new Object[] {pop, newChrom}); } pop.addChromosome(newChrom); } catch (Exception ex) { throw new RuntimeException(ex); } } } } IChromosome newFittest = reAddFittest(pop, fittest); if (monitorActive && newFittest != null) { // Monitor that fitness value of chromosomes is being updated. // ----------------------------------------------------------- a_conf .getMonitor() .event( IEvolutionMonitor.MONITOR_EVENT_READD_FITTEST, a_conf.getGenerationNr(), new Object[] {pop, fittest}); } // Increase number of generations. // ------------------------------- a_conf.incrementGenerationNr(); // Fire an event to indicate we've performed an evolution. // ------------------------------------------------------- m_lastPop = pop; m_lastConf = a_conf; a_conf .getEventManager() .fireGeneticEvent(new GeneticEvent(GeneticEvent.GENOTYPE_EVOLVED_EVENT, this)); return pop; }