org.jenetics.engine

Class Engine<G extends Gene<?,G>,C extends Comparable<? super C>>

java.lang.Object

org.jenetics.engine.Engine<G,C>

public final class Engine<G extends Gene<?,G>,C extends Comparable<? super C>>
extends Object

Genetic algorithm engine which is the main class. The following example shows the main steps in initializing and executing the GA.

public class RealFunction { // Definition of the fitness function. private static Double evaluate(final Genotype<DoubleGene> gt) { final double x = gt.getGene().doubleValue(); return cos(0.5 + sin(x)) * cos(x); } public static void main(String[] args) { // Create/configuring the engine via its builder. final Engine<DoubleGene, Double> engine = Engine .builder( RealFunction::evaluate, DoubleChromosome.of(0.0, 2.0*PI)) .populationSize(500) .optimize(Optimize.MINIMUM) .alterers( new Mutator<>(0.03), new MeanAlterer<>(0.6)) .build(); // Execute the GA (engine). final Phenotype<DoubleGene, Double> result = engine.stream() // Truncate the evolution stream if no better individual could // be found after 5 consecutive generations. .limit(bySteadyFitness(5)) // Terminate the evolution after maximal 100 generations. .limit(100) .collect(toBestPhenotype()); } }

The architecture allows to decouple the configuration of the engine from the execution. The Engine is configured via the Engine.Builder class and can't be changed after creation. The actual evolution is performed by the EvolutionStream, which is created by the Engine.

This class is thread safe: No mutable state is maintained by the engine. Therefore it is save to create multiple evolution streams with one engine, which may be actually used in different threads.

Since:

3.0

Version:

3.0 — $Date: 2014-12-28 $

Author:

Franz Wilhelmstötter

See Also:

Engine.Builder, EvolutionResult, EvolutionStream, EvolutionStatistics

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Engine.Builder<G extends Gene<?,G>,C extends Comparable<? super C>> Builder class for building GA Engine instances.

Method Summary

Modifier and Type	Method and Description
Engine.Builder<G,C>	builder() Create a new evolution Engine.Builder initialized with the values of the current evolution Engine.
static <G extends Gene<?,G>,C extends Comparable<? super C>> Engine.Builder<G,C>	builder(Function<? super Genotype<G>,? extends C> fitnessFunction, Chromosome<G> chromosome, Chromosome<G>... chromosomes) Create a new evolution Engine.Builder with the given fitness function and chromosome templates.
static <G extends Gene<?,G>,C extends Comparable<? super C>> Engine.Builder<G,C>	builder(Function<? super Genotype<G>,? extends C> fitnessFunction, Factory<Genotype<G>> genotypeFactory) Create a new evolution Engine.Builder with the given fitness function and genotype factory.
EvolutionResult<G,C>	evolve(Population<G,C> population, long generation) Perform one evolution step with the given population and generation.
Alterer<G,C>	getAlterer() Return the used Alterer of the GA.
Function<? super Genotype<G>,? extends C>	getFitnessFunction() Return the fitness function of the GA engine.
Function<? super C,? extends C>	getFitnessScaler() Return the fitness scaler of the GA engine.
Factory<Genotype<G>>	getGenotypeFactory() Return the used genotype Factory of the GA.
long	getMaximalPhenotypeAge() Return the maximal allowed phenotype age.
int	getOffspringCount() Return the number of selected offsprings.
Selector<G,C>	getOffspringSelector() Return the used offspring Selector of the GA.
Optimize	getOptimize() Return the optimization strategy.
int	getPopulationSize() Return the number of individuals of a population.
int	getSurvivorsCount() The number of selected survivors.
Selector<G,C>	getSurvivorsSelector() Return the used survivor Selector of the GA.
Iterator<EvolutionResult<G,C>>	iterator() Create a new infinite evolution iterator with a newly created population.
Iterator<EvolutionResult<G,C>>	iterator(Iterable<Genotype<G>> genotypes) Create a new infinite evolution iterator with the given initial individuals.
Iterator<EvolutionResult<G,C>>	iterator(Population<G,C> population, long generation) Create a new infinite evolution iterator with the given initial population.
EvolutionStream<G,C>	stream() Create a new infinite evolution stream with a newly created population.
EvolutionStream<G,C>	stream(Iterable<Genotype<G>> genotypes) Create a new infinite evolution stream with the given initial individuals.
EvolutionStream<G,C>	stream(Population<G,C> population, long generation) Create a new infinite evolution stream with the given initial population.

Methods inherited from class java.lang.Object

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

Method Detail

evolve

public EvolutionResult<G,C> evolve(Population<G,C> population,
                                   long generation)

Perform one evolution step with the given population and generation. New phenotypes are created with the fitness function and fitness scaler defined by this engine.

This method is thread-safe.

Parameters:

population - the population to evolve

generation - the current generation; used for calculating the phenotype age.

Returns:

the evolution result

Throws:

NullPointerException - if the given population is null

iterator

public Iterator<EvolutionResult<G,C>> iterator()

Create a new infinite evolution iterator with a newly created population. This is an alternative way for evolution. It lets the user start, stop and resume the evolution process whenever desired.

Returns:

a new infinite evolution iterator

stream

public EvolutionStream<G,C> stream()

Create a new infinite evolution stream with a newly created population.

Returns:

a new evolution stream.

stream

public EvolutionStream<G,C> stream(Iterable<Genotype<G>> genotypes)

Create a new infinite evolution stream with the given initial individuals. If an empty Iterable is given, the engines genotype factory is used for creating the population.

Parameters:

genotypes - the initial individuals used for the evolution stream. Missing individuals are created and individuals not needed are skipped.

Returns:

a new evolution stream.

Throws:

NullPointerException - if the given genotypes is null.

iterator

public Iterator<EvolutionResult<G,C>> iterator(Iterable<Genotype<G>> genotypes)

Create a new infinite evolution iterator with the given initial individuals. If an empty Iterable is given, the engines genotype factory is used for creating the population.

Parameters:

genotypes - the initial individuals used for the evolution iterator. Missing individuals are created and individuals not needed are skipped.

Returns:

a new infinite evolution iterator

Throws:

NullPointerException - if the given genotypes is null.

stream

public EvolutionStream<G,C> stream(Population<G,C> population,
                                   long generation)

Create a new infinite evolution stream with the given initial population. If an empty Population is given, the engines genotype factory is used for creating the population. The given population might be the result of an other engine and this method allows to start the evolution with the outcome of an different engine. The fitness function and the fitness scaler are replaced by the one defined for this engine.

Parameters:

population - the initial individuals used for the evolution stream. Missing individuals are created and individuals not needed are skipped.

generation - the generation the stream starts from; must be greater than zero.

Returns:

a new evolution stream.

Throws:

NullPointerException - if the given population is null.

IllegalArgumentException - if the given generation is smaller then one

iterator

public Iterator<EvolutionResult<G,C>> iterator(Population<G,C> population,
                                               long generation)

Create a new infinite evolution iterator with the given initial population. If an empty Population is given, the engines genotype factory is used for creating the population. The given population might be the result of an other engine and this method allows to start the evolution with the outcome of an different engine. The fitness function and the fitness scaler are replaced by the one defined for this engine.

Parameters:

population - the initial individuals used for the evolution iterator. Missing individuals are created and individuals not needed are skipped.

generation - the generation the iterator starts from; must be greater than zero.

Returns:

a new infinite evolution iterator

Throws:

NullPointerException - if the given population is null.

IllegalArgumentException - if the given generation is smaller then one

getFitnessFunction

public Function<? super Genotype<G>,? extends C> getFitnessFunction()

Return the fitness function of the GA engine.

Returns:

the fitness function

getFitnessScaler

public Function<? super C,? extends C> getFitnessScaler()

Return the fitness scaler of the GA engine.

Returns:

the fitness scaler

getGenotypeFactory

public Factory<Genotype<G>> getGenotypeFactory()

Return the used genotype Factory of the GA. The genotype factory is used for creating the initial population and new, random individuals when needed (as replacement for invalid and/or died genotypes).

Returns:

the used genotype Factory of the GA.

getSurvivorsSelector

public Selector<G,C> getSurvivorsSelector()

Return the used survivor Selector of the GA.

Returns:

the used survivor Selector of the GA.

getOffspringSelector

public Selector<G,C> getOffspringSelector()

Return the used offspring Selector of the GA.

Returns:

the used offspring Selector of the GA.

getAlterer

public Alterer<G,C> getAlterer()

Return the used Alterer of the GA.

Returns:

the used Alterer of the GA.

getOffspringCount

public int getOffspringCount()

Return the number of selected offsprings.

Returns:

the number of selected offsprings

getSurvivorsCount

public int getSurvivorsCount()

The number of selected survivors.

Returns:

the number of selected survivors

getPopulationSize

public int getPopulationSize()

Return the number of individuals of a population.

Returns:

the number of individuals of a population

getMaximalPhenotypeAge

public long getMaximalPhenotypeAge()

Return the maximal allowed phenotype age.

Returns:

the maximal allowed phenotype age

getOptimize

public Optimize getOptimize()

Return the optimization strategy.

Returns:

the optimization strategy

builder

public Engine.Builder<G,C> builder()

Create a new evolution Engine.Builder initialized with the values of the current evolution Engine. With this method, the evolution engine can serve as a template for an new one.

Returns:

a new engine builder

builder

public static <G extends Gene<?,G>,C extends Comparable<? super C>> Engine.Builder<G,C> builder(Function<? super Genotype<G>,? extends C> fitnessFunction,
                                                                                                Factory<Genotype<G>> genotypeFactory)

Create a new evolution Engine.Builder with the given fitness function and genotype factory.

Type Parameters:

G - the gene type

C - the fitness function result type

Parameters:

fitnessFunction - the fitness function

genotypeFactory - the genotype factory

Returns:

a new engine builder

Throws:

NullPointerException - if one of the arguments is null.

builder

@SafeVarargs
public static <G extends Gene<?,G>,C extends Comparable<? super C>> Engine.Builder<G,C> builder(Function<? super Genotype<G>,? extends C> fitnessFunction,
                                                                                                             Chromosome<G> chromosome,
                                                                                                             Chromosome<G>... chromosomes)

Create a new evolution Engine.Builder with the given fitness function and chromosome templates.

Type Parameters:

G - the gene type

C - the fitness function result type

Parameters:

fitnessFunction - the fitness function

chromosome - the first chromosome

chromosomes - the chromosome templates

Returns:

a new engine builder

Throws:

NullPointerException - if one of the arguments is null.