libstdc++
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00001 // -*- C++ -*- 00002 00003 // Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the terms 00007 // of the GNU General Public License as published by the Free Software 00008 // Foundation; either version 3, or (at your option) any later 00009 // version. 00010 00011 // This library is distributed in the hope that it will be useful, but 00012 // WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00014 // General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file parallel/random_number.h 00026 * @brief Random number generator based on the Mersenne twister. 00027 * This file is a GNU parallel extension to the Standard C++ Library. 00028 */ 00029 00030 // Written by Johannes Singler. 00031 00032 #ifndef _GLIBCXX_PARALLEL_RANDOM_NUMBER_H 00033 #define _GLIBCXX_PARALLEL_RANDOM_NUMBER_H 1 00034 00035 #include <parallel/types.h> 00036 #include <tr1/random> 00037 #include <limits> 00038 00039 namespace __gnu_parallel 00040 { 00041 /** @brief Random number generator, based on the Mersenne twister. */ 00042 class _RandomNumber 00043 { 00044 private: 00045 std::tr1::mt19937 _M_mt; 00046 uint64_t _M_supremum; 00047 uint64_t _M_rand_sup; 00048 double _M_supremum_reciprocal; 00049 double _M_rand_sup_reciprocal; 00050 00051 // Assumed to be twice as long as the usual random number. 00052 uint64_t __cache; 00053 00054 // Bit results. 00055 int __bits_left; 00056 00057 static uint32_t 00058 __scale_down(uint64_t __x, 00059 #if _GLIBCXX_SCALE_DOWN_FPU 00060 uint64_t /*_M_supremum*/, double _M_supremum_reciprocal) 00061 #else 00062 uint64_t _M_supremum, double /*_M_supremum_reciprocal*/) 00063 #endif 00064 { 00065 #if _GLIBCXX_SCALE_DOWN_FPU 00066 return uint32_t(__x * _M_supremum_reciprocal); 00067 #else 00068 return static_cast<uint32_t>(__x % _M_supremum); 00069 #endif 00070 } 00071 00072 public: 00073 /** @brief Default constructor. Seed with 0. */ 00074 _RandomNumber() 00075 : _M_mt(0), _M_supremum(0x100000000ULL), 00076 _M_rand_sup(1ULL << std::numeric_limits<uint32_t>::digits), 00077 _M_supremum_reciprocal(double(_M_supremum) / double(_M_rand_sup)), 00078 _M_rand_sup_reciprocal(1.0 / double(_M_rand_sup)), 00079 __cache(0), __bits_left(0) { } 00080 00081 /** @brief Constructor. 00082 * @param __seed Random __seed. 00083 * @param _M_supremum Generate integer random numbers in the 00084 * interval @c [0,_M_supremum). */ 00085 _RandomNumber(uint32_t __seed, uint64_t _M_supremum = 0x100000000ULL) 00086 : _M_mt(__seed), _M_supremum(_M_supremum), 00087 _M_rand_sup(1ULL << std::numeric_limits<uint32_t>::digits), 00088 _M_supremum_reciprocal(double(_M_supremum) / double(_M_rand_sup)), 00089 _M_rand_sup_reciprocal(1.0 / double(_M_rand_sup)), 00090 __cache(0), __bits_left(0) { } 00091 00092 /** @brief Generate unsigned random 32-bit integer. */ 00093 uint32_t 00094 operator()() 00095 { return __scale_down(_M_mt(), _M_supremum, _M_supremum_reciprocal); } 00096 00097 /** @brief Generate unsigned random 32-bit integer in the 00098 interval @c [0,local_supremum). */ 00099 uint32_t 00100 operator()(uint64_t local_supremum) 00101 { 00102 return __scale_down(_M_mt(), local_supremum, 00103 double(local_supremum * _M_rand_sup_reciprocal)); 00104 } 00105 00106 /** @brief Generate a number of random bits, run-time parameter. 00107 * @param __bits Number of bits to generate. */ 00108 unsigned long 00109 __genrand_bits(int __bits) 00110 { 00111 unsigned long __res = __cache & ((1 << __bits) - 1); 00112 __cache = __cache >> __bits; 00113 __bits_left -= __bits; 00114 if (__bits_left < 32) 00115 { 00116 __cache |= ((uint64_t(_M_mt())) << __bits_left); 00117 __bits_left += 32; 00118 } 00119 return __res; 00120 } 00121 }; 00122 00123 } // namespace __gnu_parallel 00124 00125 #endif /* _GLIBCXX_PARALLEL_RANDOM_NUMBER_H */