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    /*
 * Java Genetic Algorithm Library (jenetics-3.2.0).
 * Copyright (c) 2007-2015 Franz Wilhelmstötter
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Author:
 *    Franz Wilhelmstötter ([email protected])
 */
package org.jenetics.engine;

import static java.lang.String.format;

import java.time.Clock;
import java.time.Duration;
import java.util.function.Predicate;

import org.jenetics.internal.util.require;

import org.jenetics.util.NanoClock;

/**
 * This class contains factory methods for creating predicates, which can be
 * used for limiting the evolution stream.
 *
 * @see EvolutionStream#limit(Predicate)
 *
 * @author Franz Wilhelmstötter
 * @since 3.0
 * @version 3.1
 */
public final class limit {
	private limit() {require.noInstance();}

	/**
	 * Return a predicate, which will truncate the evolution stream after the
	 * given number of generations. The returned predicate behaves like a call
	 * of the {@link java.util.stream.Stream#limit(long)} and exists for
	 * completeness reasons.
	 *
	 * @since 3.1
	 *
	 * @param generation the number of generations after the evolution stream is
	 *        truncated
	 * @return a predicate which truncates the evolution stream after the given
	 *        number of generations
	 * @throws java.lang.IllegalArgumentException if the given {@code generation}
	 *         is smaller than zero.
	 */
	public static Predicate byFixedGeneration(final long generation) {
		if (generation < 0) {
			throw new IllegalArgumentException(format(
				"The number of generations must greater than one, but was %d",
				generation
			));
		}

		return new Predicate() {
			private long _current;
			@Override
			public boolean test(final Object o) {
				return ++_current < generation;
			}
		};
	}

	/**
	 * Return a predicate, which will truncate the evolution stream if no
	 * better phenotype could be found after the given number of
	 * {@code generations}.
	 *
	 * 
    {@code
	 * final Phenotype 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());
	 * }
    
	 *
	 * @param generations the number of steady generations
	 * @param  the fitness type
	 * @return a predicate which truncate the evolution stream if no better
	 *         phenotype could be found after a give number of
	 *         {@code generations}
	 * @throws IllegalArgumentException if the generation is smaller than
	 *         one.
	 */
	public static >
	Predicate> bySteadyFitness(final int generations) {
		return new SteadyFitnessLimit<>(generations);
	}

	/**
	 * 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.
	 *
	 * 
    {@code
	 * final Phenotype 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());
	 * }
    
	 *
	 * @since 3.1
	 *
	 * @param duration the duration after the evolution stream will be truncated
	 * @param clock the clock used for measure the execution time
	 * @return a predicate, which will truncate the evolution stream, based on
	 *         the exceeded execution time
	 * @throws NullPointerException if one of the arguments is {@code null}
	 */
	public static Predicate
	byExecutionTime(final Duration duration, final Clock clock) {
		return new ExecutionTimeLimit(duration, 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.
	 *
	 * 
    {@code
	 * final Phenotype 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());
	 * }
    
	 *
	 * @since 3.1
	 *
	 * @param duration the duration after the evolution stream will be truncated
	 * @return a predicate, which will truncate the evolution stream, based on
	 *         the exceeded execution time
	 * @throws NullPointerException if the evolution {@code duration} is
	 *         {@code null}
	 */
	public static Predicate
	byExecutionTime(final Duration duration) {
		return byExecutionTime(duration, NanoClock.systemUTC());
	}

	/**
	 * 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.
	 *
	 * 
    {@code
	 * final Phenotype 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());
	 * }
    
	 *
	 * @since 3.1
	 *
	 * @param threshold the desired threshold
	 * @param  the fitness type
	 * @return the predicate which truncates the evolution stream based on the
	 *         given {@code threshold}.
	 * @throws NullPointerException if the given {@code threshold} is
	 *        {@code null}.
	 */
	public static >
	Predicate> byFitnessThreshold(final C threshold) {
		return new FitnessThresholdLimit<>(threshold);
	}


}
    
    
    
    

    




    
    
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