| /* |
| * 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.math4.legacy.stat.descriptive.rank; |
| |
| import java.io.Serializable; |
| import java.io.IOException; |
| import java.io.ObjectOutputStream; |
| import java.io.ObjectInputStream; |
| import org.apache.commons.math4.legacy.core.MathArrays; |
| import org.apache.commons.rng.RestorableUniformRandomProvider; |
| import org.apache.commons.rng.simple.RandomSource; |
| import org.apache.commons.rng.core.RandomProviderDefaultState; |
| |
| /** |
| * A strategy of selecting random index between begin and end indices. |
| * |
| * @since 3.4 |
| */ |
| public class RandomPivotingStrategy implements PivotingStrategy, Serializable { |
| /** Serializable UID. */ |
| private static final long serialVersionUID = 20160517L; |
| /** Source of randomness. */ |
| private final RandomSource randomSource; |
| /** Random generator to use for selecting pivot. */ |
| private transient RestorableUniformRandomProvider random; |
| |
| /** |
| * Simple constructor. |
| * |
| * @param randomSource RNG to use for selecting pivot. |
| * @param seed Seed for initializing the RNG. |
| * |
| * @since 4.0 |
| */ |
| public RandomPivotingStrategy(RandomSource randomSource, |
| long seed) { |
| this.randomSource = randomSource; |
| random = randomSource.create(seed); |
| } |
| |
| /** |
| * {@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 org.apache.commons.math4.legacy.exception.MathIllegalArgumentException MathIllegalArgumentException when indices exceeds range |
| */ |
| @Override |
| public int pivotIndex(final double[] work, final int begin, final int end) { |
| MathArrays.verifyValues(work, begin, end - begin); |
| return begin + random.nextInt(end - begin - 1); |
| } |
| |
| /** |
| * @param out Output stream. |
| * @throws IOException if an error occurs. |
| */ |
| private void writeObject(ObjectOutputStream out) |
| throws IOException { |
| // Write non-transient fields. |
| out.defaultWriteObject(); |
| |
| // Save current state. |
| out.writeObject(((RandomProviderDefaultState) random.saveState()).getState()); |
| } |
| |
| /** |
| * @param in Input stream. |
| * @throws IOException if an error occurs. |
| * @throws ClassNotFoundException if an error occurs. |
| */ |
| private void readObject(ObjectInputStream in) |
| throws IOException, |
| ClassNotFoundException { |
| // Read non-transient fields. |
| in.defaultReadObject(); |
| |
| // Recreate the "delegate" from serialized info. |
| random = randomSource.create(); |
| // And restore its state. |
| final RandomProviderDefaultState state = new RandomProviderDefaultState((byte[]) in.readObject()); |
| random.restoreState(state); |
| } |
| } |