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.

Version:

1.0

Author:

Sean Luke

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static byte	C_EXACTLY_ONE_FIFTH_BETTER
static byte	C_OVER_ONE_FIFTH_BETTER
static byte	C_UNDER_ONE_FIFTH_BETTER
(package private) int[]	children
byte[]	comparison
int[]	count Modified by multiple threads, don't fool with this
int[]	lambda
int[]	mu
static String	P_LAMBDA
static String	P_MU
static String	P_MU_FRACTION
Population	parentPopulation
(package private) int[]	parents

Constructor Summary

Constructors

Constructor and Description
MuCommaLambdaBreeder()

Method Summary

Methods

Modifier and Type	Method and Description
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.
Population	breedPopulation(EvolutionState state) Breeds state.population, returning a new population.
int	maximumMuLambdaDivisor() lambda should be no SMALLER than mu times this value.
Population	postProcess(Population newpop, Population oldpop, EvolutionState state) A hook for Mu+Lambda, not used in Mu,Lambda
Population	setToLambda(Population pop, EvolutionState state) Sets all subpopulations in pop to the expected lambda size.
void	setup(EvolutionState state, Parameter base) Sets up the object by reading it from the parameters stored in state, built off of the parameter base base.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

P_MU

public static final String P_MU

See Also:

Constant Field Values

P_MU_FRACTION

public static final String P_MU_FRACTION

See Also:

Constant Field Values

P_LAMBDA

public static final String P_LAMBDA

See Also:

Constant Field Values

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:

Constant Field Values

C_UNDER_ONE_FIFTH_BETTER

public static final byte C_UNDER_ONE_FIFTH_BETTER

See Also:

Constant Field Values

C_EXACTLY_ONE_FIFTH_BETTER

public static final byte C_EXACTLY_ONE_FIFTH_BETTER

See Also:

Constant Field Values

count

public int[] count

Modified by multiple threads, don't fool with this

children

int[] children

parents

int[] parents

Constructor Detail

MuCommaLambdaBreeder

public MuCommaLambdaBreeder()

Method Detail

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.

setToLambda

public Population setToLambda(Population pop,
                     EvolutionState state)

Sets all subpopulations in pop to the expected lambda size. Does not fill new slots with individuals.

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.