org.jenetics.engine

Class limit

java.lang.Object

org.jenetics.engine.limit

public final class limit
extends Object

This class contains factory methods for creating predicates, which can be used for limiting the evolution stream.

Since:

3.0

Version:

3.1

Author:

Franz Wilhelmstötter

See Also:

EvolutionStream.limit(Predicate)

Method Summary

Modifier and Type	Method and Description
static Predicate<Object>	byExecutionTime(Duration duration) Return a predicate, which will truncate the evolution stream if the GA execution exceeds a given time duration.
static Predicate<Object>	byExecutionTime(Duration duration, Clock clock) Return a predicate, which will truncate the evolution stream if the GA execution exceeds a given time duration.
static <C extends Comparable<? super C>> Predicate<EvolutionResult<?,C>>	byFitnessThreshold(C threshold) Return a predicate, which will truncated the evolution stream if the best fitness of the current population becomes less than the specified threshold and the objective is set to minimize the fitness.
static Predicate<Object>	byFixedGeneration(long generation) Return a predicate, which will truncate the evolution stream after the given number of generations.
static <C extends Comparable<? super C>> Predicate<EvolutionResult<?,C>>	bySteadyFitness(int generations) Return a predicate, which will truncate the evolution stream if no better phenotype could be found after the given number of generations.

Methods inherited from class java.lang.Object

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

Method Detail

byFixedGeneration

public static Predicate<Object> byFixedGeneration(long generation)

Return a predicate, which will truncate the evolution stream after the given number of generations. The returned predicate behaves like a call of the Stream.limit(long) and exists for completeness reasons.

Parameters:

generation - the number of generations after the evolution stream is truncated

Returns:

a predicate which truncates the evolution stream after the given number of generations

Throws:

IllegalArgumentException - if the given generation is smaller than zero.

Since:

3.1

bySteadyFitness

public static <C extends Comparable<? super C>> Predicate<EvolutionResult<?,C>> bySteadyFitness(int generations)

Return a predicate, which will truncate the evolution stream if no better phenotype could be found after the given number of generations.

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());

Type Parameters:

C - the fitness type

Parameters:

generations - the number of steady generations

Returns:

a predicate which truncate the evolution stream if no better phenotype could be found after a give number of generations

Throws:

IllegalArgumentException - if the generation is smaller than one.

byExecutionTime

public static Predicate<Object> byExecutionTime(Duration duration,
                                                Clock clock)

Return a predicate, which will truncate the evolution stream if the GA execution exceeds a given time duration. This predicate is (normally) used as safety net, for guaranteed stream truncation.

final Phenotype<DoubleGene, Double> result = engine.stream() // Truncate the evolution stream after 5 "steady" generations. .limit(bySteadyFitness(5)) // The evolution will stop after maximal 500 ms. .limit(byExecutionTime(Duration.ofMillis(500), Clock.systemUTC()) .collect(toBestPhenotype());

Parameters:

duration - the duration after the evolution stream will be truncated

clock - the clock used for measure the execution time

Returns:

a predicate, which will truncate the evolution stream, based on the exceeded execution time

Throws:

NullPointerException - if one of the arguments is null

Since:

3.1

byExecutionTime

public static Predicate<Object> byExecutionTime(Duration duration)

Return a predicate, which will truncate the evolution stream if the GA execution exceeds a given time duration. This predicate is (normally) used as safety net, for guaranteed stream truncation.

final Phenotype<DoubleGene, Double> result = engine.stream() // Truncate the evolution stream after 5 "steady" generations. .limit(bySteadyFitness(5)) // The evolution will stop after maximal 500 ms. .limit(byExecutionTime(Duration.ofMillis(500)) .collect(toBestPhenotype());

Parameters:

duration - the duration after the evolution stream will be truncated

Returns:

a predicate, which will truncate the evolution stream, based on the exceeded execution time

Throws:

NullPointerException - if the evolution duration is null

Since:

3.1

byFitnessThreshold

public static <C extends Comparable<? super C>> Predicate<EvolutionResult<?,C>> byFitnessThreshold(C threshold)

Return a predicate, which will truncated the evolution stream if the best fitness of the current population becomes less than the specified threshold and the objective is set to minimize the fitness. This predicate also stops the evolution if the best fitness in the current population becomes greater than the user-specified fitness threshold when the objective is to maximize the fitness.

final Phenotype<DoubleGene, Double> result = engine.stream() // Truncate the evolution stream if the best fitness is higher than // the given threshold of '2.3'. .limit(byFitnessThreshold(2.3)) // The evolution will stop after maximal 250 generations; guarantees // the termination (truncation) of the evolution stream. .limit(250) .collect(toBestPhenotype());

Type Parameters:

C - the fitness type

Parameters:

threshold - the desired threshold

Returns:

the predicate which truncates the evolution stream based on the given threshold.

Throws:

NullPointerException - if the given threshold is null.

Since:

3.1