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?÷ // random number generation -*- C++ -*-
// Copyright (C) 2009-2013 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
// .
/**
* @file bits/random.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{random}
*/
#ifndef _RANDOM_H
#define _RANDOM_H 1
#include
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
// [26.4] Random number generation
/**
* @defgroup random Random Number Generation
* @ingroup numerics
*
* A facility for generating random numbers on selected distributions.
* @{
*/
/**
* @brief A function template for converting the output of a (integral)
* uniform random number generator to a floatng point result in the range
* [0-1).
*/
template
_RealType
generate_canonical(_UniformRandomNumberGenerator& __g);
_GLIBCXX_END_NAMESPACE_VERSION
/*
* Implementation-space details.
*/
namespace __detail
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
template
(std::numeric_limits<_UIntType>::digits)>
struct _Shift
{ static const _UIntType __value = 0; };
template
struct _Shift<_UIntType, __w, true>
{ static const _UIntType __value = _UIntType(1) << __w; };
template
struct _Select_uint_least_t
{
static_assert(__which < 0, /* needs to be dependent */
"sorry, would be too much trouble for a slow result");
};
template
struct _Select_uint_least_t<__s, 4>
{ typedef unsigned int type; };
template
struct _Select_uint_least_t<__s, 3>
{ typedef unsigned long type; };
template
struct _Select_uint_least_t<__s, 2>
{ typedef unsigned long long type; };
#ifdef _GLIBCXX_USE_INT128
template
struct _Select_uint_least_t<__s, 1>
{ typedef unsigned __int128 type; };
#endif
// Assume a != 0, a < m, c < m, x < m.
template= __m - 1),
bool __schrage_ok = __m % __a < __m / __a>
struct _Mod
{
typedef typename _Select_uint_least_t::type _Tp2;
static _Tp
__calc(_Tp __x)
{ return static_cast<_Tp>((_Tp2(__a) * __x + __c) % __m); }
};
// Schrage.
template
struct _Mod<_Tp, __m, __a, __c, false, true>
{
static _Tp
__calc(_Tp __x);
};
// Special cases:
// - for m == 2^n or m == 0, unsigned integer overflow is safe.
// - a * (m - 1) + c fits in _Tp, there is no over