1 // Optimizations for random number functions, x86 version -*- C++ -*- 2 3 // Copyright (C) 2012-2013 Free Software Foundation, Inc. 4 // 5 // This file is part of the GNU ISO C++ Library. This library is free 6 // software; you can redistribute it and/or modify it under the 7 // terms of the GNU General Public License as published by the 8 // Free Software Foundation; either version 3, or (at your option) 9 // any later version. 10 11 // This library is distributed in the hope that it will be useful, 12 // but WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 // GNU General Public License for more details. 15 16 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 /** @file bits/opt_random.h 26 * This is an internal header file, included by other library headers. 27 * Do not attempt to use it directly. @headername{random} 28 */ 29 30 #ifndef _BITS_OPT_RANDOM_H 31 #define _BITS_OPT_RANDOM_H 1 32 33 #include <x86intrin.h> 34 35 36 #pragma GCC system_header 37 38 39 namespace std _GLIBCXX_VISIBILITY(default) 40 { 41 _GLIBCXX_BEGIN_NAMESPACE_VERSION 42 43 #ifdef __SSE3__ 44 template<> 45 template<typename _UniformRandomNumberGenerator> 46 void 47 normal_distribution<double>:: 48 __generate(typename normal_distribution<double>::result_type* __f, 49 typename normal_distribution<double>::result_type* __t, 50 _UniformRandomNumberGenerator& __urng, 51 const param_type& __param) 52 { 53 typedef uint64_t __uctype; 54 55 if (__f == __t) 56 return; 57 58 if (_M_saved_available) 59 { 60 _M_saved_available = false; 61 *__f++ = _M_saved * __param.stddev() + __param.mean(); 62 63 if (__f == __t) 64 return; 65 } 66 67 constexpr uint64_t __maskval = 0xfffffffffffffull; 68 static const __m128i __mask = _mm_set1_epi64x(__maskval); 69 static const __m128i __two = _mm_set1_epi64x(0x4000000000000000ull); 70 static const __m128d __three = _mm_set1_pd(3.0); 71 const __m128d __av = _mm_set1_pd(__param.mean()); 72 73 const __uctype __urngmin = __urng.min(); 74 const __uctype __urngmax = __urng.max(); 75 const __uctype __urngrange = __urngmax - __urngmin; 76 const __uctype __uerngrange = __urngrange + 1; 77 78 while (__f + 1 < __t) 79 { 80 double __le; 81 __m128d __x; 82 do 83 { 84 union 85 { 86 __m128i __i; 87 __m128d __d; 88 } __v; 89 90 if (__urngrange > __maskval) 91 { 92 if (__detail::_Power_of_2(__uerngrange)) 93 __v.__i = _mm_and_si128(_mm_set_epi64x(__urng(), 94 __urng()), 95 __mask); 96 else 97 { 98 const __uctype __uerange = __maskval + 1; 99 const __uctype __scaling = __urngrange / __uerange; 100 const __uctype __past = __uerange * __scaling; 101 uint64_t __v1; 102 do 103 __v1 = __uctype(__urng()) - __urngmin; 104 while (__v1 >= __past); 105 __v1 /= __scaling; 106 uint64_t __v2; 107 do 108 __v2 = __uctype(__urng()) - __urngmin; 109 while (__v2 >= __past); 110 __v2 /= __scaling; 111 112 __v.__i = _mm_set_epi64x(__v1, __v2); 113 } 114 } 115 else if (__urngrange == __maskval) 116 __v.__i = _mm_set_epi64x(__urng(), __urng()); 117 else if ((__urngrange + 2) * __urngrange >= __maskval 118 && __detail::_Power_of_2(__uerngrange)) 119 { 120 uint64_t __v1 = __urng() * __uerngrange + __urng(); 121 uint64_t __v2 = __urng() * __uerngrange + __urng(); 122 123 __v.__i = _mm_and_si128(_mm_set_epi64x(__v1, __v2), 124 __mask); 125 } 126 else 127 { 128 size_t __nrng = 2; 129 __uctype __high = __maskval / __uerngrange / __uerngrange; 130 while (__high > __uerngrange) 131 { 132 ++__nrng; 133 __high /= __uerngrange; 134 } 135 const __uctype __highrange = __high + 1; 136 const __uctype __scaling = __urngrange / __highrange; 137 const __uctype __past = __highrange * __scaling; 138 __uctype __tmp; 139 140 uint64_t __v1; 141 do 142 { 143 do 144 __tmp = __uctype(__urng()) - __urngmin; 145 while (__tmp >= __past); 146 __v1 = __tmp / __scaling; 147 for (size_t __cnt = 0; __cnt < __nrng; ++__cnt) 148 { 149 __tmp = __v1; 150 __v1 *= __uerngrange; 151 __v1 += __uctype(__urng()) - __urngmin; 152 } 153 } 154 while (__v1 > __maskval || __v1 < __tmp); 155 156 uint64_t __v2; 157 do 158 { 159 do 160 __tmp = __uctype(__urng()) - __urngmin; 161 while (__tmp >= __past); 162 __v2 = __tmp / __scaling; 163 for (size_t __cnt = 0; __cnt < __nrng; ++__cnt) 164 { 165 __tmp = __v2; 166 __v2 *= __uerngrange; 167 __v2 += __uctype(__urng()) - __urngmin; 168 } 169 } 170 while (__v2 > __maskval || __v2 < __tmp); 171 172 __v.__i = _mm_set_epi64x(__v1, __v2); 173 } 174 175 __v.__i = _mm_or_si128(__v.__i, __two); 176 __x = _mm_sub_pd(__v.__d, __three); 177 __m128d __m = _mm_mul_pd(__x, __x); 178 __le = _mm_cvtsd_f64(_mm_hadd_pd (__m, __m)); 179 } 180 while (__le == 0.0 || __le >= 1.0); 181 182 double __mult = (std::sqrt(-2.0 * std::log(__le) / __le) 183 * __param.stddev()); 184 185 __x = _mm_add_pd(_mm_mul_pd(__x, _mm_set1_pd(__mult)), __av); 186 187 _mm_storeu_pd(__f, __x); 188 __f += 2; 189 } 190 191 if (__f != __t) 192 { 193 result_type __x, __y, __r2; 194 195 __detail::_Adaptor<_UniformRandomNumberGenerator, result_type> 196 __aurng(__urng); 197 198 do 199 { 200 __x = result_type(2.0) * __aurng() - 1.0; 201 __y = result_type(2.0) * __aurng() - 1.0; 202 __r2 = __x * __x + __y * __y; 203 } 204 while (__r2 > 1.0 || __r2 == 0.0); 205 206 const result_type __mult = std::sqrt(-2 * std::log(__r2) / __r2); 207 _M_saved = __x * __mult; 208 _M_saved_available = true; 209 *__f = __y * __mult * __param.stddev() + __param.mean(); 210 } 211 } 212 #endif 213 214 215 _GLIBCXX_END_NAMESPACE_VERSION 216 } // namespace 217 218 219 #endif // _BITS_OPT_RANDOM_H 220
