Documentation of 'org.jgap.impl.SwappingMutationOperator' Java class
SwappingMutationOperator
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org.jgap.impl

Class SwappingMutationOperator

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Comparable, Configurable, GeneticOperator

    public class SwappingMutationOperator
extends MutationOperator
    Swaps the genes instead of mutating them. This kind of operator is required by Traveling Salesman Problem. See J. Grefenstette, R. Gopal, R. Rosmaita, and D. Gucht. Genetic algorithms for the traveling salesman problem. In Proceedings of the Second International Conference on Genetic Algorithms. Lawrence Eribaum Associates, Mahwah, NJ, 1985. and also Sushil J. Louis & Gong Li }
    Since:
    2.0
    See Also:
    Serialized Form

    • Constructor Detail

      • SwappingMutationOperator

        public SwappingMutationOperator(Configuration a_config,
                                IUniversalRateCalculator a_mutationRateCalculator)
                         throws InvalidConfigurationException
        Constructs a new instance of this operator with a specified mutation rate calculator, which results in dynamic mutation being turned on.
        Parameters:
        a_config - the configuration to use
        a_mutationRateCalculator - calculator for dynamic mutation rate computation
        Throws:
        InvalidConfigurationException
        Since:
        3.0 (previously: without a_config)

      • SwappingMutationOperator

        public SwappingMutationOperator(Configuration a_config,
                                int a_desiredMutationRate)
                         throws InvalidConfigurationException
        Constructs a new instance of this MutationOperator with the given mutation rate.
        Parameters:
        a_config - the configuration to use
        a_desiredMutationRate - desired rate of mutation, expressed as the denominator of the 1 / X fraction. For example, 1000 would result in 1/1000 genes being mutated on average. A mutation rate of zero disables mutation entirely
        Throws:
        InvalidConfigurationException
        Since:
        3.0 (previously: without a_config)

    • Method Detail

      • operate

        public void operate(Population a_population,
                    java.util.List a_candidateChromosomes)
        Description copied from interface: GeneticOperator
        The operate method will be invoked on each of the genetic operators referenced by the current Configuration object during the evolution phase. Operators are given an opportunity to run in the order that they are added to the Configuration. Implementations of this method may reference the population of Chromosomes as it was at the beginning of the evolutionary phase and/or they may instead reference the candidate Chromosomes, which are the results of prior genetic operators. In either case, only Chromosomes added to the list of candidate chromosomes will be considered for natural selection. The parameters a_population and a_candidateChromosomes may refer to the same list of chromosomes for performance issues. Thus would mean an in-place modification. In ealier JGAP versions it was suggested never modifying the input population. Please refer to implementations delivered with JGAP to get a picture of the way non-susceptible in-place modifications are possible. If wrongly done, ConcurrentModificationException could be risen when accessing the population by an iterator in a GeneticOperator. Or, if population.getChromosomes().size() was used inside a loop where chromosomes were added to the input population this could lead to an infinite loop in worst case.
        Specified by:
        operate in interface GeneticOperator
        Overrides:
        operate in class MutationOperator
        Parameters:
        a_population - the population of chromosomes from the current evolution prior to exposure to any genetic operators. Chromosomes in this array should not be modified. Please, notice, that the call in Genotype.evolve() to the implementations of GeneticOperator overgoes this due to performance issues
        a_candidateChromosomes - the pool of chromosomes that have been selected for the next evolved population
        Since:
        2.0

      • setStartOffset

        public void setStartOffset(int a_offset)
        Sets a number of genes at the start of chromosome, that are excluded from the swapping. In the Salesman task, the first city in the list should (where the salesman leaves from) probably should not change as it is part of the list. The default value is 1.
        Parameters:
        a_offset - the offset to set
        Since:
        2.0

      • getStartOffset

        public int getStartOffset()
        Gets a number of genes at the start of chromosome, that are excluded from the swapping. In the Salesman task, the first city in the list should (where the salesman leaves from) probably should not change as it is part of the list. The default value is 1.
        Returns:
        the start offset
        Since:
        2.0
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