org.jenetics.engine

Interface EvolutionStream<G extends Gene<?,G>,C extends Comparable<? super C>>

All Superinterfaces:

AutoCloseable, BaseStream<EvolutionResult<G,C>,Stream<EvolutionResult<G,C>>>, Stream<EvolutionResult<G,C>>

public interface EvolutionStream<G extends Gene<?,G>,C extends Comparable<? super C>>
extends Stream<EvolutionResult<G,C>>

The EvolutionStream class extends the Java Stream and adds a method for limiting the evolution by a given predicate.

Since:

3.0

Version:

3.1

Author:

Franz Wilhelmstötter

See Also:

Stream, Engine

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.stream.Stream

Stream.Builder<T>

Method Summary

Modifier and Type	Method and Description
EvolutionStream<G,C>	limit(Predicate<? super EvolutionResult<G,C>> proceed) Returns a stream consisting of the elements of this stream, truncated when the given proceed predicate returns false.
static <G extends Gene<?,G>,C extends Comparable<? super C>> EvolutionStream<G,C>	of(Supplier<EvolutionStart<G,C>> start, Function<? super EvolutionStart<G,C>,EvolutionResult<G,C>> evolution) Create a new EvolutionStream from the given start population and evolution function.

Methods inherited from interface java.util.stream.Stream

allMatch, anyMatch, builder, collect, collect, concat, count, distinct, empty, filter, findAny, findFirst, flatMap, flatMapToDouble, flatMapToInt, flatMapToLong, forEach, forEachOrdered, generate, iterate, limit, map, mapToDouble, mapToInt, mapToLong, max, min, noneMatch, of, of, peek, reduce, reduce, reduce, skip, sorted, sorted, toArray, toArray

Methods inherited from interface java.util.stream.BaseStream

close, isParallel, iterator, onClose, parallel, sequential, spliterator, unordered

Method Detail

limit

EvolutionStream<G,C> limit(Predicate<? super EvolutionResult<G,C>> proceed)

Returns a stream consisting of the elements of this stream, truncated when the given proceed predicate returns false.

General usage example:

final Phenotype<DoubleGene, Double> result = engine.stream() // Truncate the evolution stream after 5 "steady" generations. .limit(bySteadyFitness(5)) // The evolution will stop after maximal 100 generations. .limit(100) .collect(toBestPhenotype());

Parameters:

proceed - the predicate which determines whether the stream is truncated or not. If the predicate returns false, the evolution stream is truncated.

Returns:

the new stream

Throws:

NullPointerException - if the given predicate is null.

See Also:

limit

of

static <G extends Gene<?,G>,C extends Comparable<? super C>> EvolutionStream<G,C> of(Supplier<EvolutionStart<G,C>> start,
                                                                                     Function<? super EvolutionStart<G,C>,EvolutionResult<G,C>> evolution)

Create a new EvolutionStream from the given start population and evolution function. The main purpose of this factory method is to simplify the creation of an EvolutionStream from an own evolution (GA) engine.

final Supplier<EvolutionStart<DoubleGene, Double>> start = ... final EvolutionStream<DoubleGene, Double> stream = EvolutionStream.of(start, new MySpecialEngine());

A more complete example for would look like as:

public final class SpecialEngine { // The fitness function. private static Double fitness(final Genotype<DoubleGene> gt) { return gt.getGene().getAllele(); } // Create new evolution start object. private static EvolutionStart<DoubleGene, Double> start(final int populationSize, final long generation) { final Population<DoubleGene, Double> population = Genotype.of(DoubleChromosome.of(0, 1)).instances() .map(gt -> Phenotype.of(gt, generation, SpecialEngine::fitness)) .limit(populationSize) .collect(Population.toPopulation()); return EvolutionStart.of(population, generation); } // The special evolution function. private static EvolutionResult<DoubleGene, Double> evolve(final EvolutionStart<DoubleGene, Double> start) { // Your special evolution implementation comes here! return null; } public static void main(final String[] args) { final Genotype<DoubleGene> best = EvolutionStream .of(() -> start(50, 0), SpecialEngine::evolve) .limit(limit.bySteadyFitness(10)) .limit(1000) .collect(EvolutionResult.toBestGenotype()); System.out.println(String.format("Best Genotype: %s", best)); } }

Type Parameters:

G - the gene type

C - the fitness type

Parameters:

start - the evolution start

evolution - the evolution function

Returns:

a new EvolutionStream with the given start and evolution function

Throws:

NullPointerException - if one of the arguments is null

Since:

3.1