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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
package org.apache.commons.math3.util;
import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.random.RandomGenerator;
import java.io.Serializable;
/**
* A strategy of selecting random index between begin and end indices.
*
* @since 3.4
*/
public class RandomPivotingStrategy implements PivotingStrategyInterface, Serializable {
/** Serializable UID. */
private static final long serialVersionUID = 20140713L;
/** Random generator to use for selecting pivot. */
private final RandomGenerator random;
/**
* Simple constructor.
*
* @param random random generator to use for selecting pivot
*/
public RandomPivotingStrategy(final RandomGenerator random) {
this.random = random;
}
/**
* {@inheritDoc} A uniform random pivot selection between begin and end indices
*
* @return The index corresponding to a random uniformly selected value between first and the
* last indices of the array slice
* @throws MathIllegalArgumentException when indices exceeds range
*/
public int pivotIndex(final double[] work, final int begin, final int end)
throws MathIllegalArgumentException {
MathArrays.verifyValues(work, begin, end - begin);
return begin + random.nextInt(end - begin - 1);
}
}
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