bits/opt_random.h
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// Optimizations for random number functions, x86 version -*- C++ -*-
// Copyright (C) 2012-2013 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file bits/opt_random.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{random}
*/
#ifndef _BITS_OPT_RANDOM_H
#define _BITS_OPT_RANDOM_H 1
#include <x86intrin.h>
#pragma GCC system_header
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
#ifdef __SSE3__
template<>
template<typename _UniformRandomNumberGenerator>
void
normal_distribution<double>::
__generate(typename normal_distribution<double>::result_type* __f,
typename normal_distribution<double>::result_type* __t,
_UniformRandomNumberGenerator& __urng,
const param_type& __param)
{
typedef uint64_t __uctype;
if (__f == __t)
return;
if (_M_saved_available)
{
_M_saved_available = false;
*__f++ = _M_saved * __param.stddev() + __param.mean();
if (__f == __t)
return;
}
constexpr uint64_t __maskval = 0xfffffffffffffull;
static const __m128i __mask = _mm_set1_epi64x(__maskval);
static const __m128i __two = _mm_set1_epi64x(0x4000000000000000ull);
static const __m128d __three = _mm_set1_pd(3.0);
const __m128d __av = _mm_set1_pd(__param.mean());
const __uctype __urngmin = __urng.min();
const __uctype __urngmax = __urng.max();
const __uctype __urngrange = __urngmax - __urngmin;
const __uctype __uerngrange = __urngrange + 1;
while (__f + 1 < __t)
{
double __le;
__m128d __x;
do
{
union
{
__m128i __i;
__m128d __d;
} __v;
if (__urngrange > __maskval)
{
if (__detail::_Power_of_2(__uerngrange))
__v.__i = _mm_and_si128(_mm_set_epi64x(__urng(),
__urng()),
__mask);
else
{
const __uctype __uerange = __maskval + 1;
const __uctype __scaling = __urngrange / __uerange;
const __uctype __past = __uerange * __scaling;
uint64_t __v1;
do
__v1 = __uctype(__urng()) - __urngmin;
while (__v1 >= __past);
__v1 /= __scaling;
uint64_t __v2;
do
__v2 = __uctype(__urng()) - __urngmin;
while (__v2 >= __past);
__v2 /= __scaling;
__v.__i = _mm_set_epi64x(__v1, __v2);
}
}
else if (__urngrange == __maskval)
__v.__i = _mm_set_epi64x(__urng(), __urng());
else if ((__urngrange + 2) * __urngrange >= __maskval
&& __detail::_Power_of_2(__uerngrange))
{
uint64_t __v1 = __urng() * __uerngrange + __urng();
uint64_t __v2 = __urng() * __uerngrange + __urng();
__v.__i = _mm_and_si128(_mm_set_epi64x(__v1, __v2),
__mask);
}
else
{
size_t __nrng = 2;
__uctype __high = __maskval / __uerngrange / __uerngrange;
while (__high > __uerngrange)
{
++__nrng;
__high /= __uerngrange;
}
const __uctype __highrange = __high + 1;
const __uctype __scaling = __urngrange / __highrange;
const __uctype __past = __highrange * __scaling;
__uctype __tmp;
uint64_t __v1;
do
{
do
__tmp = __uctype(__urng()) - __urngmin;
while (__tmp >= __past);
__v1 = __tmp / __scaling;
for (size_t __cnt = 0; __cnt < __nrng; ++__cnt)
{
__tmp = __v1;
__v1 *= __uerngrange;
__v1 += __uctype(__urng()) - __urngmin;
}
}
while (__v1 > __maskval || __v1 < __tmp);
uint64_t __v2;
do
{
do
__tmp = __uctype(__urng()) - __urngmin;
while (__tmp >= __past);
__v2 = __tmp / __scaling;
for (size_t __cnt = 0; __cnt < __nrng; ++__cnt)
{
__tmp = __v2;
__v2 *= __uerngrange;
__v2 += __uctype(__urng()) - __urngmin;
}
}
while (__v2 > __maskval || __v2 < __tmp);
__v.__i = _mm_set_epi64x(__v1, __v2);
}
__v.__i = _mm_or_si128(__v.__i, __two);
__x = _mm_sub_pd(__v.__d, __three);
__m128d __m = _mm_mul_pd(__x, __x);
__le = _mm_cvtsd_f64(_mm_hadd_pd (__m, __m));
}
while (__le == 0.0 || __le >= 1.0);
double __mult = (std::sqrt(-2.0 * std::log(__le) / __le)
* __param.stddev());
__x = _mm_add_pd(_mm_mul_pd(__x, _mm_set1_pd(__mult)), __av);
_mm_storeu_pd(__f, __x);
__f += 2;
}
if (__f != __t)
{
result_type __x, __y, __r2;
__detail::_Adaptor<_UniformRandomNumberGenerator, result_type>
__aurng(__urng);
do
{
__x = result_type(2.0) * __aurng() - 1.0;
__y = result_type(2.0) * __aurng() - 1.0;
__r2 = __x * __x + __y * __y;
}
while (__r2 > 1.0 || __r2 == 0.0);
const result_type __mult = std::sqrt(-2 * std::log(__r2) / __r2);
_M_saved = __x * __mult;
_M_saved_available = true;
*__f = __y * __mult * __param.stddev() + __param.mean();
}
}
#endif
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif // _BITS_OPT_RANDOM_H