Package ec.es

Class MuCommaLambdaBreeder

java.lang.Object
ec.Breeder
ec.es.MuCommaLambdaBreeder
All Implemented Interfaces:
Setup, Singleton, Serializable
Direct Known Subclasses:
MuPlusLambdaBreeder
public class MuCommaLambdaBreeder extends Breeder
MuCommaLambdaBreeder is a Breeder which, together with ESSelection, implements the (mu,lambda) breeding strategy and gathers the comparison data you can use to implement a 1/5-rule mutation mechanism.

Evolution strategies breeders require a "mu" parameter and a "lambda" parameter for each subpopulation. "mu" refers to the number of parents from which the new population will be built. "lambda" refers to the number of children generated by the mu parents. Subpopulation sizes will change as necessary to accommodate this fact in later generations. The only rule for initial subpopulation sizes is that they must be greater than or equal to the mu parameter for that subpopulation.

You can now set your initial subpopulation size to whatever you like, totally independent of lambda and mu, as long as it is >= mu.

MuCommaLambdaBreeder stores mu and lambda values for each subpopulation in the population, as well as comparisons. A comparison tells you if >1/5, <1/5 or =1/5 of the new population was better than its parents (the so-called evolution strategies "one-fifth rule". Although the comparisons are gathered, no mutation objects are provided which actually use them -- you're free to use them in any mutation objects you care to devise which requires them.

To do evolution strategies evolution, the breeding pipelines should contain at least one ESSelection selection method. While a child is being generated by the pipeline, the ESSelection object will return a parent from the pool of mu parents. The particular parent is chosen round-robin, so all the parents will have an equal number of children. It's perfectly fine to have more than one ESSelection object in the tree, or to call the same one repeatedly during the course of generating a child; all such objects will consistently return the same parent. They only increment to the next parent in the pool of mu parents after the child has been created from the pipeline. You can also mix ESSelection operators with other operators (like Tournament Selection). But you ought to have at least one ESSelection operator in the pipeline -- else it wouldn't be Evolution Strategies, would it?

Parameters

es.lambda.subpop-num
int >= 0		Specifies the 'lambda' parameter for the subpopulation.
es.mu.subpop-num
int: a multiple of "lambda"		Specifies the 'mu' parameter for the subpopulation.
See Also:

  • Field Details

    • P_MU

      public static final String P_MU
      See Also:

    • P_MU_FRACTION

      public static final String P_MU_FRACTION
      See Also:

    • P_LAMBDA

      public static final String P_LAMBDA
      See Also:

    • mu

      public int[] mu

    • lambda

      public int[] lambda

    • parentPopulation

      public Population parentPopulation

    • comparison

      public byte[] comparison

    • C_OVER_ONE_FIFTH_BETTER

      public static final byte C_OVER_ONE_FIFTH_BETTER
      See Also:

    • C_UNDER_ONE_FIFTH_BETTER

      public static final byte C_UNDER_ONE_FIFTH_BETTER
      See Also:

    • C_EXACTLY_ONE_FIFTH_BETTER

      public static final byte C_EXACTLY_ONE_FIFTH_BETTER
      See Also:

    • newIndividuals

      public ArrayList[][] newIndividuals

    • count

      public int[] count
      Modified by multiple threads, don't fool with this

  • Constructor Details

    • MuCommaLambdaBreeder

      public MuCommaLambdaBreeder()

  • Method Details

    • maximumMuLambdaDivisor

      public int maximumMuLambdaDivisor()
      lambda should be no SMALLER than mu times this value. This varies between (mu,lambda) (where it's 2) and (mu + lambda) (where it's 1).

    • setup

      public void setup(EvolutionState state, Parameter base)
      Description copied from interface: Setup
      Sets up the object by reading it from the parameters stored in state, built off of the parameter base base. If an ancestor implements this method, be sure to call super.setup(state,base); before you do anything else.

    • breedPopulation

      public Population breedPopulation(EvolutionState state)
      Description copied from class: Breeder
      Breeds state.population, returning a new population. In general, state.population should not be modified.
      Specified by:
      breedPopulation in class Breeder

    • postProcess

      public Population postProcess(Population newpop, Population oldpop, EvolutionState state)
      A hook for Mu+Lambda, not used in Mu,Lambda

    • breedPopChunk

      public void breedPopChunk(Population newpop, EvolutionState state, int[] numinds, int[] from, int threadnum)
      A private helper function for breedPopulation which breeds a chunk of individuals in a subpopulation for a given thread. Although this method is declared public (for the benefit of a private helper class in this file), you should not call it.