Example usage for org.apache.commons.math3.genetics Population nextGeneration

Introduction

In this page you can find the example usage for org.apache.commons.math3.genetics Population nextGeneration.

Prototype

Population nextGeneration();

Source Link

Document

Start the population for the next generation.

Usage

From source file:eu.tsp.sal.SensorGeneticAlgorithm.java

/**
 * Evolve the given population into the next generation.
 * <p>//from  w  ww. jav a 2s. c om
 * <ol>
 *  <li>Get nextGeneration population to fill from <code>current</code>
 *      generation, using its nextGeneration method</li>
 *  <li>Loop until new generation is filled:</li>
 *  <ul><li>Apply configured SelectionPolicy to select a pair of parents
 *          from <code>current</code></li>
 *      <li>With probability = {@link #getCrossoverRate()}, apply
 *          configured {@link CrossoverPolicy} to parents</li>
 *      <li>With probability = {@link #getMutationRate()}, apply
 *          configured {@link MutationPolicy} to each of the offspring</li>
 *      <li>Add offspring individually to nextGeneration,
 *          space permitting</li>
 *  </ul>
 *  <li>Return nextGeneration</li>
 * </ol>
 *
 * @param current the current population.
 * @return the population for the next generation.
 */
public Population nextGeneration(final Population current) {
    Population nextGeneration = current.nextGeneration();

    RandomGenerator randGen = getRandomGenerator();

    while (nextGeneration.getPopulationSize() < nextGeneration.getPopulationLimit()) {
        // select parent chromosomes
        ChromosomePair pair = getSelectionPolicy().select(current);
        //System.out.println("*****" + pair);

        // crossover?
        if (randGen.nextDouble() < getCrossoverRate()) {
            // apply crossover policy to create two offspring
            pair = getCrossoverPolicy().crossover(pair.getFirst(), pair.getSecond());
        }

        // mutation?
        if (randGen.nextDouble() < getMutationRate()) {
            // apply mutation policy to the chromosomes
            pair = new ChromosomePair(getMutationPolicy().mutate(pair.getFirst()),
                    getMutationPolicy().mutate(pair.getSecond()));
        }

        // add the first chromosome to the population
        nextGeneration.addChromosome(pair.getFirst());
        // is there still a place for the second chromosome?
        if (nextGeneration.getPopulationSize() < nextGeneration.getPopulationLimit()) {
            // add the second chromosome to the population
            nextGeneration.addChromosome(pair.getSecond());
        }
    }

    System.out.println("\nGeneration (iteration): " + (generationsEvolved + 1));
    WSN.printPopulation(nextGeneration);

    return nextGeneration;
}

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