1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.math4.legacy.stat.descriptive.rank; 18 19 import org.apache.commons.math4.legacy.core.MathArrays; 20 import org.apache.commons.rng.RestorableUniformRandomProvider; 21 import org.apache.commons.rng.simple.RandomSource; 22 23 /** 24 * A strategy of selecting random index between begin and end indices. 25 * 26 * @since 3.4 27 */ 28 public class RandomPivotingStrategy implements PivotingStrategy { 29 /** Source of randomness. */ 30 private final RandomSource randomSource; 31 /** Random generator to use for selecting pivot. */ 32 private transient RestorableUniformRandomProvider random; 33 34 /** 35 * Simple constructor. 36 * 37 * @param randomSource RNG to use for selecting pivot. 38 * @param seed Seed for initializing the RNG. 39 * 40 * @since 4.0 41 */ 42 public RandomPivotingStrategy(RandomSource randomSource, 43 long seed) { 44 this.randomSource = randomSource; 45 random = randomSource.create(seed); 46 } 47 48 /** 49 * {@inheritDoc} 50 * 51 * A uniform random pivot selection between begin and end indices. 52 * 53 * @return The index corresponding to a random uniformly selected 54 * value between first and the last indices of the array slice 55 * @throws org.apache.commons.math4.legacy.exception.MathIllegalArgumentException MathIllegalArgumentException when indices exceeds range 56 */ 57 @Override 58 public int pivotIndex(final double[] work, final int begin, final int end) { 59 MathArrays.verifyValues(work, begin, end - begin); 60 return begin + random.nextInt(end - begin - 1); 61 } 62 }