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1 /*
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2 Copyright 2008,2009,2012 Stéphane De Mita, Mathieu Siol
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3 Adapted from MStrat, developed by Charles-Edouard Coste,
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4 Thomas M. Bataillon, Mathieu Cotisson, Guy Decoux, Chistophe Rozale,
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5 Daniel J. Schoen and Jacques L. David.
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6
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7 This file is part of the EggLib library.
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8
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9 EggLib is free software: you can redistribute it and/or modify
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10 it under the terms of the GNU General Public License as published by
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11 the Free Software Foundation, either version 3 of the License, or
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12 (at your option) any later version.
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13
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14 EggLib is distributed in the hope that it will be useful,
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15 but WITHOUT ANY WARRANTY; without even the implied warranty of
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16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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17 GNU General Public License for more details.
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18
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19 You should have received a copy of the GNU General Public License
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20 along with EggLib. If not, see <http://www.gnu.org/licenses/>.
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21 */
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22
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23 #ifndef EGGLIB_RANDOM_HPP
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24 #define EGGLIB_RANDOM_HPP
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25
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26 namespace egglib {
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27
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28 /** \brief Pseudo-random number generator
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29 *
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30 * \ingroup core
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31 *
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32 * Random is a pseudo-random number generator, adapted from a part of MStrat,
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33 * developed by Charles-Edouard Coste, Thomas M. Bataillon, Mathieu Cotisson,
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34 * Guy Decoux, Chistophe Rozale, Daniel J. Schoen and Jacques L. David.
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35 *
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36 * It uses two different seeds. By default, they are initialized to available
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37 * arbitrary values. However, a given sequence can be repeated by passing the
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38 * same two seeds.
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39 *
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40 */
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41 class Random {
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42 public:
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43 /** \brief Initializes using default seeds
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44 *
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45 * Uses the current system time and the memory address of the object as an attempt to generate unique sequences.
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46 */
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47 Random();
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48
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49 /** \brief Initializes using given seeds
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50 *
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51 * This constructor can be used to reproduce a given sequence.
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52 */
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53 Random(double seed1, double seed2);
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54
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55 /** \brief Draws a number from an exponential distribution
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56 *
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57 * \param expectation the distribution mean (also 1/lambda
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58 * where lambda is the rate parameter).
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59 *
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60 */
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61 double erand(double expectation);
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62
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63 /** \brief Draws an integer from a uniform distribution bound by 0 and max (max is not included)
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64 *
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65 * max is not included.
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66 *
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67 */
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68 unsigned int irand(unsigned int max);
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69
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70 /** \brief Draws an integer from a Poisson distribution with parameter p
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71 *
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72 * The Poisson transformation algorithm was taken from (in French)
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73 * http://www.u-picardie.fr/~cochard/IEM/demos/C107/C107_3.htm.
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74 */
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75 unsigned int prand(double p);
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76
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77 /** \brief Draws a number from a normal distribution of expectation 0 and variance 1
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78 *
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79 * The algorithm used is the polar form of the Box-Muller
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80 * algorithm. \todo use the Ziggurat algorithm for the
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81 * nrand() method of Random.
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82 *
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83 */
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84 double nrand();
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85
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86 /** \brief Draws a number from a geometric law
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87 *
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88 * \param param the parameter of the law
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89 *
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90 */
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91 unsigned int grand(double);
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92
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93 /** \brief Draws a number from a uniform distribution between 0 and 1
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94 *
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95 */
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96 double uniform();
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97
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98 /** \brief Gets the current value of the first seed
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99 *
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100 */
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101 double seed1() const;
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102
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103 /** \brief Gets the current value of the second seed
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104 *
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105 */
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106 double seed2() const;
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107
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108 /** \brief Sets the current value of the first seed
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109 *
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110 */
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111 void seed1(double);
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112
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113 /** \brief Sets the current value of the second seed
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114 *
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115 */
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116 void seed2(double);
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117
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118 private:
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119 // First seed
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120 double _seed1;
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121
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122 // Second seed
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123 double _seed2;
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124
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125 /* since the normal random generator draws two numbers at
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126 * a time, one is cached and returned at any subsequent call
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127 */
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128 bool b_ncached;
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129 double v_ncached;
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130
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131 };
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132 }
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133
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134 #endif
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