[5484] | 1 | #region License Information |
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| 2 | /* HeuristicLab |
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[14185] | 3 | * Copyright (C) 2002-2016 Heuristic and Evolutionary Algorithms Laboratory (HEAL) |
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[5484] | 4 | * |
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| 5 | * This file is part of HeuristicLab. |
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| 6 | * |
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| 7 | * HeuristicLab is free software: you can redistribute it and/or modify |
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| 8 | * it under the terms of the GNU General Public License as published by |
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| 9 | * the Free Software Foundation, either version 3 of the License, or |
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| 10 | * (at your option) any later version. |
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| 11 | * |
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| 12 | * HeuristicLab is distributed in the hope that it will be useful, |
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| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 15 | * GNU General Public License for more details. |
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| 16 | * |
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| 17 | * You should have received a copy of the GNU General Public License |
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| 18 | * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>. |
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| 19 | */ |
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| 20 | #endregion |
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| 21 | |
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| 22 | using System; |
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| 23 | using System.Collections.Generic; |
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[7812] | 24 | using System.Linq; |
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| 25 | using HeuristicLab.Core; |
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[5484] | 26 | |
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| 27 | namespace HeuristicLab.Random { |
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[7812] | 28 | public static class RandomEnumerable { |
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[5484] | 29 | public static IEnumerable<int> SampleRandomNumbers(int maxElement, int count) { |
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| 30 | return SampleRandomNumbers(Environment.TickCount, 0, maxElement, count); |
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| 31 | } |
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| 32 | |
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| 33 | public static IEnumerable<int> SampleRandomNumbers(int start, int end, int count) { |
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| 34 | return SampleRandomNumbers(Environment.TickCount, start, end, count); |
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| 35 | } |
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| 36 | |
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| 37 | //algorithm taken from progamming pearls page 127 |
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[10466] | 38 | //IMPORTANT because IEnumerables with yield are used the seed must be specified to return always |
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[5484] | 39 | //the same sequence of numbers without caching the values. |
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| 40 | public static IEnumerable<int> SampleRandomNumbers(int seed, int start, int end, int count) { |
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| 41 | int remaining = end - start; |
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| 42 | var mt = new FastRandom(seed); |
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| 43 | for (int i = start; i < end && count > 0; i++) { |
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| 44 | double probability = mt.NextDouble(); |
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| 45 | if (probability < ((double)count) / remaining) { |
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| 46 | count--; |
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| 47 | yield return i; |
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| 48 | } |
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| 49 | remaining--; |
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| 50 | } |
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| 51 | } |
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[7812] | 52 | |
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| 53 | /// <summary> |
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| 54 | /// Chooses one elements from a sequence giving each element an equal chance. |
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| 55 | /// </summary> |
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| 56 | /// <remarks> |
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| 57 | /// Runtime complexity is O(1) for sequences that are of type <see cref="IList{T}"/> and |
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| 58 | /// O(N) for all other. |
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| 59 | /// </remarks> |
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| 60 | /// <exception cref="ArgumentException">If the sequence is empty.</exception> |
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| 61 | /// <typeparam name="T">The type of the items to be selected.</typeparam> |
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| 62 | /// <param name="source">The sequence of elements.</param> |
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| 63 | /// <param name="random">The random number generator to use, its NextDouble() method must produce values in the range [0;1)</param> |
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| 64 | /// <param name="count">The number of items to be selected.</param> |
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| 65 | /// <returns>An element that has been chosen randomly from the sequence.</returns> |
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| 66 | public static T SampleRandom<T>(this IEnumerable<T> source, IRandom random) { |
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| 67 | if (!source.Any()) throw new ArgumentException("sequence is empty.", "source"); |
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| 68 | return source.SampleRandom(random, 1).First(); |
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| 69 | } |
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| 70 | |
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| 71 | /// <summary> |
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| 72 | /// Chooses <paramref name="count"/> elements from a sequence with repetition with equal chances for each element. |
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| 73 | /// </summary> |
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| 74 | /// <remarks> |
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| 75 | /// Runtime complexity is O(count) for sequences that are <see cref="IList{T}"/> and |
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| 76 | /// O(N * count) for all other. No exception is thrown if the sequence is empty. |
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| 77 | /// |
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| 78 | /// The method is online. |
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| 79 | /// </remarks> |
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| 80 | /// <typeparam name="T">The type of the items to be selected.</typeparam> |
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| 81 | /// <param name="source">The sequence of elements.</param> |
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| 82 | /// <param name="random">The random number generator to use, its NextDouble() method must produce values in the range [0;1)</param> |
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| 83 | /// <param name="count">The number of items to be selected.</param> |
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| 84 | /// <returns>A sequence of elements that have been chosen randomly.</returns> |
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| 85 | public static IEnumerable<T> SampleRandom<T>(this IEnumerable<T> source, IRandom random, int count) { |
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| 86 | var listSource = source as IList<T>; |
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| 87 | if (listSource != null) { |
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| 88 | while (count > 0) { |
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| 89 | yield return listSource[random.Next(listSource.Count)]; |
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| 90 | count--; |
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| 91 | } |
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| 92 | } else { |
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| 93 | while (count > 0) { |
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| 94 | var enumerator = source.GetEnumerator(); |
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| 95 | enumerator.MoveNext(); |
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| 96 | T selectedItem = enumerator.Current; |
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| 97 | int counter = 1; |
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| 98 | while (enumerator.MoveNext()) { |
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| 99 | counter++; |
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| 100 | if (counter * random.NextDouble() < 1.0) |
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| 101 | selectedItem = enumerator.Current; |
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| 102 | } |
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| 103 | yield return selectedItem; |
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| 104 | count--; |
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| 105 | } |
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| 106 | } |
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| 107 | } |
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| 108 | |
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| 109 | /// <summary> |
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| 110 | /// Chooses <paramref name="count"/> elements from a sequence without repetition with equal chances for each element. |
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| 111 | /// The items are returned in the same order as they appear in the sequence. |
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| 112 | /// </summary> |
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| 113 | /// <remarks> |
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| 114 | /// Runtime complexity is O(N) for all sequences. |
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| 115 | /// No exception is thrown if the sequence contains less items than there are to be selected. |
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| 116 | /// |
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| 117 | /// The method is online. |
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| 118 | /// </remarks> |
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| 119 | /// <typeparam name="T">The type of the items to be selected.</typeparam> |
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| 120 | /// <param name="source">The sequence of elements.</param> |
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| 121 | /// <param name="random">The random number generator to use, its NextDouble() method must produce values in the range [0;1)</param> |
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| 122 | /// <param name="count">The number of items to be selected.</param> |
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[9072] | 123 | /// <param name="sourceCount">Optional parameter specifying the number of elements in the source enumerations</param> |
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[7812] | 124 | /// <returns>A sequence of elements that have been chosen randomly.</returns> |
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[9072] | 125 | public static IEnumerable<T> SampleRandomWithoutRepetition<T>(this IEnumerable<T> source, IRandom random, int count, int sourceCount = -1) { |
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| 126 | if (sourceCount == -1) sourceCount = source.Count(); |
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| 127 | int remaining = sourceCount; |
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[7812] | 128 | foreach (var item in source) { |
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| 129 | if (random.NextDouble() * remaining < count) { |
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| 130 | count--; |
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| 131 | yield return item; |
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| 132 | if (count <= 0) break; |
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| 133 | } |
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| 134 | remaining--; |
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| 135 | } |
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| 136 | } |
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| 137 | |
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| 138 | /// <summary> |
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| 139 | /// Chooses elements out of a sequence with repetition. The chance that an item is selected is proportional or inverse-proportional |
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| 140 | /// to the <paramref name="weights"/>. |
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| 141 | /// </summary> |
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| 142 | /// <remarks> |
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| 143 | /// In case both <paramref name="inverseProportional"/> and <paramref name="windowing"/> are false values must be > 0, |
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| 144 | /// otherwise an InvalidOperationException is thrown. |
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| 145 | /// |
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| 146 | /// The method internally holds two arrays: One that is the sequence itself and another one for the values. |
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| 147 | /// </remarks> |
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| 148 | /// <typeparam name="T">The type of the items to be selected.</typeparam> |
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| 149 | /// <param name="source">The sequence of elements.</param> |
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| 150 | /// <param name="random">The random number generator to use, its NextDouble() method must produce values in the range [0;1)</param> |
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| 151 | /// <param name="count">The number of items to be selected.</param> |
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| 152 | /// <param name="weights">The weight values for the items.</param> |
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| 153 | /// <param name="windowing">Whether to scale the proportional values or not.</param> |
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| 154 | /// <param name="inverseProportional">Determines whether to choose proportionally (false) or inverse-proportionally (true).</param> |
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| 155 | /// <returns>A sequence of selected items. The sequence might contain the same item more than once.</returns> |
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| 156 | public static IEnumerable<T> SampleProportional<T>(this IEnumerable<T> source, IRandom random, int count, IEnumerable<double> weights, bool windowing = true, bool inverseProportional = false) { |
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| 157 | return source.SampleProportional(random, weights, windowing, inverseProportional).Take(count); |
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| 158 | } |
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| 159 | |
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| 160 | /// <summary> |
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| 161 | /// Same as <seealso cref="SampleProportional<T>"/>, but chooses an item exactly once. |
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| 162 | /// </summary> |
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| 163 | /// <remarks> |
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| 164 | /// In case both <paramref name="inverseProportional"/> and <paramref name="windowing"/> are false values must be > 0, |
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| 165 | /// otherwise an InvalidOperationException is thrown. |
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| 166 | /// |
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| 167 | /// The method internally holds two arrays: One that is the sequence itself and another one for the values. |
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[10466] | 168 | /// |
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| 169 | /// The method does not check if the number of elements in source and weights are the same. |
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[7812] | 170 | /// </remarks> |
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| 171 | /// <typeparam name="T">The type of the items to be selected.</typeparam> |
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| 172 | /// <param name="source">The sequence of elements.</param> |
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| 173 | /// <param name="random">The random number generator to use, its NextDouble() method must produce values in the range [0;1)</param> |
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| 174 | /// <param name="count">The number of items to be selected.</param> |
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| 175 | /// <param name="weights">The weight values for the items.</param> |
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| 176 | /// <param name="windowing">Whether to scale the proportional values or not.</param> |
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[10466] | 177 | /// <param name="inverseProportional">Determines whether to choose proportionally (true) or inverse-proportionally (false).</param> |
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| 178 | /// <returns>A sequence of selected items. Might actually be shorter than <paramref name="count"/> elements if source has less than <paramref name="count"/> elements.</returns> |
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[7812] | 179 | public static IEnumerable<T> SampleProportionalWithoutRepetition<T>(this IEnumerable<T> source, IRandom random, int count, IEnumerable<double> weights, bool windowing = true, bool inverseProportional = false) { |
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| 180 | return source.SampleProportionalWithoutRepetition(random, weights, windowing, inverseProportional).Take(count); |
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| 181 | } |
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| 182 | #region Proportional Helpers |
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| 183 | private static IEnumerable<T> SampleProportional<T>(this IEnumerable<T> source, IRandom random, IEnumerable<double> weights, bool windowing, bool inverseProportional) { |
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| 184 | var sourceArray = source.ToArray(); |
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[10503] | 185 | var valueArray = PrepareProportional(weights, windowing, inverseProportional); |
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[7812] | 186 | double total = valueArray.Sum(); |
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| 187 | |
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| 188 | while (true) { |
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| 189 | int index = 0; |
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| 190 | double ball = valueArray[index], sum = random.NextDouble() * total; |
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| 191 | while (ball < sum) |
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| 192 | ball += valueArray[++index]; |
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| 193 | yield return sourceArray[index]; |
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| 194 | } |
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| 195 | } |
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| 196 | private static IEnumerable<T> SampleProportionalWithoutRepetition<T>(this IEnumerable<T> source, IRandom random, IEnumerable<double> weights, bool windowing, bool inverseProportional) { |
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[10503] | 197 | var valueArray = PrepareProportional(weights, windowing, inverseProportional); |
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[10466] | 198 | var list = new LinkedList<Tuple<T, double>>(source.Zip(valueArray, Tuple.Create)); |
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[7812] | 199 | double total = valueArray.Sum(); |
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| 200 | |
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[10503] | 201 | while (list.Count > 0) { |
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| 202 | var cur = list.First; |
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[10466] | 203 | double ball = cur.Value.Item2, sum = random.NextDouble() * total; // assert: sum < total. When there is only one item remaining: sum < ball |
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[7812] | 204 | while (ball < sum) { |
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[10466] | 205 | cur = cur.Next; |
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| 206 | ball += cur.Value.Item2; |
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[7812] | 207 | } |
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[10466] | 208 | yield return cur.Value.Item1; |
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| 209 | list.Remove(cur); |
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| 210 | total -= cur.Value.Item2; |
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[7812] | 211 | } |
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| 212 | } |
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[10466] | 213 | |
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[14420] | 214 | public static double[] PrepareProportional(IEnumerable<double> weights, bool windowing, bool inverseProportional) { |
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[7812] | 215 | double maxValue = double.MinValue, minValue = double.MaxValue; |
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[10503] | 216 | double[] valueArray = weights.ToArray(); |
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[7812] | 217 | |
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[10503] | 218 | for (int i = 0; i < valueArray.Length; i++) { |
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[7812] | 219 | if (valueArray[i] > maxValue) maxValue = valueArray[i]; |
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| 220 | if (valueArray[i] < minValue) minValue = valueArray[i]; |
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| 221 | } |
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| 222 | if (minValue == maxValue) { // all values are equal |
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[10503] | 223 | for (int i = 0; i < valueArray.Length; i++) { |
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[7812] | 224 | valueArray[i] = 1.0; |
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| 225 | } |
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| 226 | } else { |
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| 227 | if (windowing) { |
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[7828] | 228 | if (inverseProportional) InverseProportionalScale(valueArray, maxValue); |
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| 229 | else ProportionalScale(valueArray, minValue); |
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[7812] | 230 | } else { |
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| 231 | if (minValue < 0.0) throw new InvalidOperationException("Proportional selection without windowing does not work with values < 0."); |
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| 232 | if (inverseProportional) InverseProportionalScale(valueArray, 2 * maxValue); |
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| 233 | } |
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| 234 | } |
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| 235 | return valueArray; |
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| 236 | } |
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| 237 | private static void ProportionalScale(double[] values, double minValue) { |
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| 238 | for (int i = 0; i < values.Length; i++) { |
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| 239 | values[i] = values[i] - minValue; |
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| 240 | } |
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| 241 | } |
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| 242 | private static void InverseProportionalScale(double[] values, double maxValue) { |
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| 243 | for (int i = 0; i < values.Length; i++) { |
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| 244 | values[i] = maxValue - values[i]; |
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| 245 | } |
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| 246 | } |
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| 247 | #endregion |
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| 248 | |
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| 249 | /// <summary> |
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| 250 | /// Shuffles an enumerable and returns a new enumerable according to the Fisher-Yates shuffle. |
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| 251 | /// </summary> |
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| 252 | /// <remarks> |
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| 253 | /// Note that the source enumerable is transformed into an array. |
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| 254 | /// |
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| 255 | /// The implementation is described in http://stackoverflow.com/questions/1287567/c-is-using-random-and-orderby-a-good-shuffle-algorithm. |
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| 256 | /// </remarks> |
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| 257 | /// <typeparam name="T">The type of the items that are to be shuffled.</typeparam> |
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| 258 | /// <param name="source">The enumerable that contains the items.</param> |
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| 259 | /// <param name="random">The random number generator, its Next(n) method must deliver uniformly distributed random numbers in the range [0;n).</param> |
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| 260 | /// <returns>An enumerable with the elements shuffled.</returns> |
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| 261 | public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> source, IRandom random) { |
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| 262 | T[] elements = source.ToArray(); |
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| 263 | for (int i = elements.Length - 1; i > 0; i--) { |
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| 264 | // Swap element "i" with a random earlier element (including itself) |
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| 265 | int swapIndex = random.Next(i + 1); |
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| 266 | yield return elements[swapIndex]; |
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| 267 | elements[swapIndex] = elements[i]; |
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| 268 | // we don't actually perform the swap, we can forget about the |
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| 269 | // swapped element because we already returned it. |
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| 270 | } |
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[14544] | 271 | if (elements.Length > 0) |
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| 272 | yield return elements[0]; |
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[7812] | 273 | } |
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[5484] | 274 | } |
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| 275 | } |
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[10466] | 276 | |
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