libstdc++-v3/config/cpu/i486/opt/bits/opt_random.h

   1 // Optimizations for random number functions, x86 version -*- C++ -*-
   2
   3 // Copyright (C) 2012 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 = UINT64_C(0xfffffffffffff);
  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