1 // Optimizations for random number functions, x86 version -*- C++ -*-
3 // Copyright (C) 2012-2015 Free Software Foundation, Inc.
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)
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.
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.
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/>.
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}
30 #ifndef _BITS_OPT_RANDOM_H
31 #define _BITS_OPT_RANDOM_H 1
33 #include <x86intrin.h>
36 #pragma GCC system_header
39 namespace std _GLIBCXX_VISIBILITY(default)
41 _GLIBCXX_BEGIN_NAMESPACE_VERSION
45 template<typename _UniformRandomNumberGenerator>
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)
53 typedef uint64_t __uctype;
58 if (_M_saved_available)
60 _M_saved_available = false;
61 *__f++ = _M_saved * __param.stddev() + __param.mean();
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());
73 const __uctype __urngmin = __urng.min();
74 const __uctype __urngmax = __urng.max();
75 const __uctype __urngrange = __urngmax - __urngmin;
76 const __uctype __uerngrange = __urngrange + 1;
90 if (__urngrange > __maskval)
92 if (__detail::_Power_of_2(__uerngrange))
93 __v.__i = _mm_and_si128(_mm_set_epi64x(__urng(),
98 const __uctype __uerange = __maskval + 1;
99 const __uctype __scaling = __urngrange / __uerange;
100 const __uctype __past = __uerange * __scaling;
103 __v1 = __uctype(__urng()) - __urngmin;
104 while (__v1 >= __past);
108 __v2 = __uctype(__urng()) - __urngmin;
109 while (__v2 >= __past);
112 __v.__i = _mm_set_epi64x(__v1, __v2);
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))
120 uint64_t __v1 = __urng() * __uerngrange + __urng();
121 uint64_t __v2 = __urng() * __uerngrange + __urng();
123 __v.__i = _mm_and_si128(_mm_set_epi64x(__v1, __v2),
129 __uctype __high = __maskval / __uerngrange / __uerngrange;
130 while (__high > __uerngrange)
133 __high /= __uerngrange;
135 const __uctype __highrange = __high + 1;
136 const __uctype __scaling = __urngrange / __highrange;
137 const __uctype __past = __highrange * __scaling;
144 __tmp = __uctype(__urng()) - __urngmin;
145 while (__tmp >= __past);
146 __v1 = __tmp / __scaling;
147 for (size_t __cnt = 0; __cnt < __nrng; ++__cnt)
150 __v1 *= __uerngrange;
151 __v1 += __uctype(__urng()) - __urngmin;
154 while (__v1 > __maskval || __v1 < __tmp);
160 __tmp = __uctype(__urng()) - __urngmin;
161 while (__tmp >= __past);
162 __v2 = __tmp / __scaling;
163 for (size_t __cnt = 0; __cnt < __nrng; ++__cnt)
166 __v2 *= __uerngrange;
167 __v2 += __uctype(__urng()) - __urngmin;
170 while (__v2 > __maskval || __v2 < __tmp);
172 __v.__i = _mm_set_epi64x(__v1, __v2);
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));
180 while (__le == 0.0 || __le >= 1.0);
182 double __mult = (std::sqrt(-2.0 * std::log(__le) / __le)
185 __x = _mm_add_pd(_mm_mul_pd(__x, _mm_set1_pd(__mult)), __av);
187 _mm_storeu_pd(__f, __x);
193 result_type __x, __y, __r2;
195 __detail::_Adaptor<_UniformRandomNumberGenerator, result_type>
200 __x = result_type(2.0) * __aurng() - 1.0;
201 __y = result_type(2.0) * __aurng() - 1.0;
202 __r2 = __x * __x + __y * __y;
204 while (__r2 > 1.0 || __r2 == 0.0);
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();
215 _GLIBCXX_END_NAMESPACE_VERSION
219 #endif // _BITS_OPT_RANDOM_H