Package ec

Class BreedingSource

java.lang.Object

ec.BreedingSource

All Implemented Interfaces:

Prototype, Setup, RandomChoiceChooserD, Serializable, Cloneable

Direct Known Subclasses:

BreedingPipeline, SelectionMethod

public abstract class BreedingSource
extends Object
implements Prototype, RandomChoiceChooserD

A BreedingSource is a Prototype which provides Individuals to populate new populations based on old ones. The BreedingSource/BreedingPipeline/SelectionMethod mechanism is inherently designed to work within single subpopulations, which is by far the most common case. If for some reason you need to breed among different subpopulations to produce new ones in a manner that can't be handled with exchanges, you will probably have to write your own custom Breeder; you'd have to write your own custom breeding pipelines anyway of course, though you can probably get away with reusing the SelectionMethods.

A BreedingSource may have parent sources which feed it as well. Some BreedingSources, SelectionMethods, are meant solely to plug into other BreedingSources, BreedingPipelines. BreedingPipelines can plug into other BreedingPipelines, and can also be used to provide the final Individual meant to populate a new generation.

Think of BreedingSources as Streams of Individuals; at one end of the stream is the provider, a SelectionMethod, which picks individuals from the old population. At the other end of the stream is a BreedingPipeline which hands you the finished product, a small set of new Individuals for you to use in populating your new population.

Parameters

base.prob 0.0 <= double <= 1.0, or undefined

(probability this BreedingSource gets chosen. Undefined is only valid if the caller of this BreedingSource doesn't need a probability)

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final double	NO_PROBABILITY
static final String	P_PROB
double	probability	The probability that this BreedingSource will be chosen to breed over other BreedingSources.

Constructor Summary

Constructors

Constructor	Description
BreedingSource()

Method Summary

Modifier and Type	Method	Description
Object	clone()	Creates a new individual cloned from a prototype, and suitable to begin use in its own evolutionary context.
void	fillStubs(EvolutionState state, BreedingSource source)
abstract void	finishProducing(EvolutionState state, int subpopulation, int thread)	Called after produce(...), usually once a generation, or maybe only once if you're doing steady-state evolution (at the end of the run).
final double	getProbability(Object obj)	Returns obj's probability
static int	pickRandom(BreedingSource[] sources, double prob)	Picks a random source from an array of sources, with their probabilities normalized and summed as follows: For example, if four breeding source probabilities are {0.3, 0.2, 0.1, 0.4}, then they should get normalized and summed by the outside owners as: {0.3, 0.5, 0.6, 1.0}.
void	preparePipeline(Object hook)	A hook which should be passed to all your subsidiary breeding sources.
abstract void	prepareToProduce(EvolutionState state, int subpopulation, int thread)	Called before produce(...), usually once a generation, or maybe only once if you're doing steady-state evolution, to let the breeding source "warm up" prior to producing.
abstract int	produce(int min, int max, int subpopulation, ArrayList<Individual> inds, EvolutionState state, int thread, HashMap<String,Object> misc)	Produces n individuals from the given subpopulation and puts them into inds[start...start+n-1], where n = Min(Max(q,min),max), where q is the "typical" number of individuals the BreedingSource produces in one shot, and returns n.
abstract boolean	produces(EvolutionState state, Population newpop, int subpopulation, int thread)	Returns true if this BreedingSource, when attached to the given subpopulation, will produce individuals of the subpopulation's species.
final void	setProbability(Object obj, double prob)	Sets obj's probability
void	setup(EvolutionState state, Parameter base)	Sets up the BreedingPipeline.
static void	setupProbabilities(BreedingSource[] sources)	Normalizes and arranges the probabilities in sources so that they are usable by pickRandom(...).
abstract int	typicalIndsProduced()	Returns the "typical" number of individuals generated with one call of produce(...).

Methods inherited from class java.lang.Object

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

Methods inherited from interface ec.Prototype

defaultBase

Field Details

P_PROB

public static final String P_PROB

See Also:

• Constant Field Values

NO_PROBABILITY

public static final double NO_PROBABILITY

See Also:

• Constant Field Values

probability

public double probability

The probability that this BreedingSource will be chosen to breed over other BreedingSources. This may or may not be used, depending on what the caller to this BreedingSource is. It also might be modified by external sources owning this object, for their own purposes. A BreedingSource should not use it for any purpose of its own, nor modify it except when setting it up.

The most common modification is to normalize it with some other set of probabilities, then set all of them up in increasing summation; this allows the use of the fast static BreedingSource-picking utility method, BreedingSource.pickRandom(...). In order to use this method, for example, if four breeding source probabilities are {0.3, 0.2, 0.1, 0.4}, then they should get normalized and summed by the outside owners as: {0.3, 0.5, 0.6, 1.0}.

Constructor Details

BreedingSource

public BreedingSource()

Method Details

setup

public void setup(EvolutionState state,
 Parameter base)

Sets up the BreedingPipeline. You can use state.output.error here because the top-level caller promises to call exitIfErrors() after calling setup. Note that probability might get modified again by an external source if it doesn't normalize right.

The most common modification is to normalize it with some other set of probabilities, then set all of them up in increasing summation; this allows the use of the fast static BreedingSource-picking utility method, BreedingSource.pickRandom(...). In order to use this method, for example, if four breeding source probabilities are {0.3, 0.2, 0.1, 0.4}, then they should get normalized and summed by the outside owners as: {0.3, 0.5, 0.6, 1.0}.

Specified by:

setup in interface Prototype

Specified by:

setup in interface Setup

See Also:

• Prototype.setup(EvolutionState,Parameter)

getProbability

public final double getProbability(Object obj)

Description copied from interface: RandomChoiceChooserD

Returns obj's probability

Specified by:

getProbability in interface RandomChoiceChooserD

setProbability

public final void setProbability(Object obj,
 double prob)

Description copied from interface: RandomChoiceChooserD

Sets obj's probability

Specified by:

setProbability in interface RandomChoiceChooserD

pickRandom

public static int pickRandom(BreedingSource[] sources,
 double prob)

Picks a random source from an array of sources, with their probabilities normalized and summed as follows: For example, if four breeding source probabilities are {0.3, 0.2, 0.1, 0.4}, then they should get normalized and summed by the outside owners as: {0.3, 0.5, 0.6, 1.0}.

setupProbabilities

public static void setupProbabilities(BreedingSource[] sources)

Normalizes and arranges the probabilities in sources so that they are usable by pickRandom(...). If the sources have all zero probabilities, then a uniform selection is used. Negative probabilities will generate an ArithmeticException, as will an empty source array.

typicalIndsProduced

public abstract int typicalIndsProduced()

Returns the "typical" number of individuals generated with one call of produce(...).

produces

public abstract boolean produces(EvolutionState state,
 Population newpop,
 int subpopulation,
 int thread)

Returns true if this BreedingSource, when attached to the given subpopulation, will produce individuals of the subpopulation's species. SelectionMethods should additionally make sure that their Fitnesses are of a valid type, if necessary. newpop *may* be the same as state.population

prepareToProduce

public abstract void prepareToProduce(EvolutionState state,
 int subpopulation,
 int thread)

Called before produce(...), usually once a generation, or maybe only once if you're doing steady-state evolution, to let the breeding source "warm up" prior to producing. Individuals should be produced from old individuals in positions [start...start+length] in the subpopulation only. May be called again to reset the BreedingSource for a whole 'nuther subpopulation.

finishProducing

public abstract void finishProducing(EvolutionState state,
 int subpopulation,
 int thread)

Called after produce(...), usually once a generation, or maybe only once if you're doing steady-state evolution (at the end of the run).

produce

public abstract int produce(int min,
 int max,
 int subpopulation,
 ArrayList<Individual> inds,
 EvolutionState state,
 int thread,
 HashMap<String,Object> misc)

Produces n individuals from the given subpopulation and puts them into inds[start...start+n-1], where n = Min(Max(q,min),max), where q is the "typical" number of individuals the BreedingSource produces in one shot, and returns n. max must be >= min, and min must be >= 1. For example, crossover might typically produce two individuals, tournament selection might typically produce a single individual, etc.

clone

public Object clone()

Description copied from interface: Prototype

Creates a new individual cloned from a prototype, and suitable to begin use in its own evolutionary context.

Typically this should be a full "deep" clone. However, you may share certain elements with other objects rather than clone hem, depending on the situation:

• If you hold objects which are shared with other instances, don't clone them.
• If you hold objects which must be unique, clone them.
• If you hold objects which were given to you as a gesture of kindness, and aren't owned by you, you probably shouldn't clone them.
• DON'T attempt to clone: Singletons, Cliques, or Populations, or Subpopulation.
• Arrays are not cloned automatically; you may need to clone an array if you're not sharing it with other instances. Arrays have the nice feature of being copyable by calling clone() on them.

Implementations.

• If no ancestor of yours implements clone(), and you have no need to do clone deeply, and you are abstract, then you should not declare clone().
• If no ancestor of yours implements clone(), and you have no need to do clone deeply, and you are not abstract, then you should implement it as follows:

   public Object clone() 
       {
       try
           { 
           return super.clone();
           }
       catch ((CloneNotSupportedException e)
           { throw new InternalError(); } // never happens
       }
          

• If no ancestor of yours implements clone(), but you need to deep-clone some things, then you should implement it as follows:

   public Object clone() 
       {
       try
           { 
           MyObject myobj = (MyObject) (super.clone());
  
           // put your deep-cloning code here...
           }
       catch ((CloneNotSupportedException e)
           { throw new InternalError(); } // never happens
       return myobj;
       } 
          

• If an ancestor has implemented clone(), and you also need to deep clone some things, then you should implement it as follows:

   public Object clone() 
       { 
       MyObject myobj = (MyObject) (super.clone());
  
       // put your deep-cloning code here...
  
       return myobj;
       } 
          

Specified by:

clone in interface Prototype

Overrides:

clone in class Object

fillStubs

public void fillStubs(EvolutionState state,
 BreedingSource source)

preparePipeline

public void preparePipeline(Object hook)

A hook which should be passed to all your subsidiary breeding sources. The default does this for you already, so ordinarily you don't need to change anything. If you are a BreedingPipeline and you implement your sources in a way different than using the sources[] array, be sure to override this method so that it calls preparePipeline(hook) on all of your sources.

ECJ at present does not custom-implement or call this method: it's available for you. Becuase it has custom functionality, this method might get called more than once, and by various objects as needed. If you use it, you should determine somehow how to use it to send information under the assumption that it might be sent by nested items in the pipeline; you don't want to scribble over each other's calls! Note that this method should travel *all* breeding source paths regardless of whether or not it's redundant to do so.