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llvm-project/libcxx/include/__random/linear_congruential_engine.h

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___RANDOM_LINEAR_CONGRUENTIAL_ENGINE_H
#define _LIBCPP___RANDOM_LINEAR_CONGRUENTIAL_ENGINE_H
#include <__config>
#include <__random/is_seed_sequence.h>
#include <cstdint>
#include <iosfwd>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
template <unsigned long long __a, unsigned long long __c,
unsigned long long __m, unsigned long long _Mp,
bool _MightOverflow = (__a != 0 && __m != 0 && __m-1 > (_Mp-__c)/__a),
bool _OverflowOK = ((__m | (__m-1)) > __m), // m = 2^n
bool _SchrageOK = (__a != 0 && __m != 0 && __m % __a <= __m / __a)> // r <= q
struct __lce_alg_picker
{
static_assert(__a != 0 || __m != 0 || !_MightOverflow || _OverflowOK || _SchrageOK,
"The current values of a, c, and m cannot generate a number "
"within bounds of linear_congruential_engine.");
static _LIBCPP_CONSTEXPR const bool __use_schrage = _MightOverflow &&
!_OverflowOK &&
_SchrageOK;
};
template <unsigned long long __a, unsigned long long __c,
unsigned long long __m, unsigned long long _Mp,
bool _UseSchrage = __lce_alg_picker<__a, __c, __m, _Mp>::__use_schrage>
struct __lce_ta;
// 64
template <unsigned long long __a, unsigned long long __c, unsigned long long __m>
struct __lce_ta<__a, __c, __m, (unsigned long long)(~0), true>
{
typedef unsigned long long result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
// Schrage's algorithm
const result_type __q = __m / __a;
const result_type __r = __m % __a;
const result_type __t0 = __a * (__x % __q);
const result_type __t1 = __r * (__x / __q);
__x = __t0 + (__t0 < __t1) * __m - __t1;
__x += __c - (__x >= __m - __c) * __m;
return __x;
}
};
template <unsigned long long __a, unsigned long long __m>
struct __lce_ta<__a, 0, __m, (unsigned long long)(~0), true>
{
typedef unsigned long long result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
// Schrage's algorithm
const result_type __q = __m / __a;
const result_type __r = __m % __a;
const result_type __t0 = __a * (__x % __q);
const result_type __t1 = __r * (__x / __q);
__x = __t0 + (__t0 < __t1) * __m - __t1;
return __x;
}
};
template <unsigned long long __a, unsigned long long __c, unsigned long long __m>
struct __lce_ta<__a, __c, __m, (unsigned long long)(~0), false>
{
typedef unsigned long long result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
return (__a * __x + __c) % __m;
}
};
template <unsigned long long __a, unsigned long long __c>
struct __lce_ta<__a, __c, 0, (unsigned long long)(~0), false>
{
typedef unsigned long long result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
return __a * __x + __c;
}
};
// 32
template <unsigned long long _Ap, unsigned long long _Cp, unsigned long long _Mp>
struct __lce_ta<_Ap, _Cp, _Mp, unsigned(~0), true>
{
typedef unsigned result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
const result_type __a = static_cast<result_type>(_Ap);
const result_type __c = static_cast<result_type>(_Cp);
const result_type __m = static_cast<result_type>(_Mp);
// Schrage's algorithm
const result_type __q = __m / __a;
const result_type __r = __m % __a;
const result_type __t0 = __a * (__x % __q);
const result_type __t1 = __r * (__x / __q);
__x = __t0 + (__t0 < __t1) * __m - __t1;
__x += __c - (__x >= __m - __c) * __m;
return __x;
}
};
template <unsigned long long _Ap, unsigned long long _Mp>
struct __lce_ta<_Ap, 0, _Mp, unsigned(~0), true>
{
typedef unsigned result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
const result_type __a = static_cast<result_type>(_Ap);
const result_type __m = static_cast<result_type>(_Mp);
// Schrage's algorithm
const result_type __q = __m / __a;
const result_type __r = __m % __a;
const result_type __t0 = __a * (__x % __q);
const result_type __t1 = __r * (__x / __q);
__x = __t0 + (__t0 < __t1) * __m - __t1;
return __x;
}
};
template <unsigned long long _Ap, unsigned long long _Cp, unsigned long long _Mp>
struct __lce_ta<_Ap, _Cp, _Mp, unsigned(~0), false>
{
typedef unsigned result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
const result_type __a = static_cast<result_type>(_Ap);
const result_type __c = static_cast<result_type>(_Cp);
const result_type __m = static_cast<result_type>(_Mp);
return (__a * __x + __c) % __m;
}
};
template <unsigned long long _Ap, unsigned long long _Cp>
struct __lce_ta<_Ap, _Cp, 0, unsigned(~0), false>
{
typedef unsigned result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
const result_type __a = static_cast<result_type>(_Ap);
const result_type __c = static_cast<result_type>(_Cp);
return __a * __x + __c;
}
};
// 16
template <unsigned long long __a, unsigned long long __c, unsigned long long __m, bool __b>
struct __lce_ta<__a, __c, __m, (unsigned short)(~0), __b>
{
typedef unsigned short result_type;
_LIBCPP_INLINE_VISIBILITY
static result_type next(result_type __x)
{
return static_cast<result_type>(__lce_ta<__a, __c, __m, unsigned(~0)>::next(__x));
}
};
template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
class _LIBCPP_TEMPLATE_VIS linear_congruential_engine;
template <class _CharT, class _Traits,
class _Up, _Up _Ap, _Up _Cp, _Up _Np>
_LIBCPP_INLINE_VISIBILITY
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const linear_congruential_engine<_Up, _Ap, _Cp, _Np>&);
template <class _CharT, class _Traits,
class _Up, _Up _Ap, _Up _Cp, _Up _Np>
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
linear_congruential_engine<_Up, _Ap, _Cp, _Np>& __x);
template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
class _LIBCPP_TEMPLATE_VIS linear_congruential_engine
{
public:
// types
typedef _UIntType result_type;
private:
result_type __x_;
static _LIBCPP_CONSTEXPR const result_type _Mp = result_type(~0);
static_assert(__m == 0 || __a < __m, "linear_congruential_engine invalid parameters");
static_assert(__m == 0 || __c < __m, "linear_congruential_engine invalid parameters");
static_assert(is_unsigned<_UIntType>::value, "_UIntType must be unsigned type");
public:
static _LIBCPP_CONSTEXPR const result_type _Min = __c == 0u ? 1u: 0u;
static _LIBCPP_CONSTEXPR const result_type _Max = __m - 1u;
static_assert(_Min < _Max, "linear_congruential_engine invalid parameters");
// engine characteristics
static _LIBCPP_CONSTEXPR const result_type multiplier = __a;
static _LIBCPP_CONSTEXPR const result_type increment = __c;
static _LIBCPP_CONSTEXPR const result_type modulus = __m;
_LIBCPP_INLINE_VISIBILITY
static _LIBCPP_CONSTEXPR result_type min() {return _Min;}
_LIBCPP_INLINE_VISIBILITY
static _LIBCPP_CONSTEXPR result_type max() {return _Max;}
static _LIBCPP_CONSTEXPR const result_type default_seed = 1u;
// constructors and seeding functions
#ifndef _LIBCPP_CXX03_LANG
_LIBCPP_INLINE_VISIBILITY
linear_congruential_engine() : linear_congruential_engine(default_seed) {}
_LIBCPP_INLINE_VISIBILITY
explicit linear_congruential_engine(result_type __s) { seed(__s); }
#else
_LIBCPP_INLINE_VISIBILITY
explicit linear_congruential_engine(result_type __s = default_seed) {
seed(__s);
}
#endif
template<class _Sseq>
_LIBCPP_INLINE_VISIBILITY
explicit linear_congruential_engine(_Sseq& __q,
typename enable_if<__is_seed_sequence<_Sseq, linear_congruential_engine>::value>::type* = 0)
{seed(__q);}
_LIBCPP_INLINE_VISIBILITY
void seed(result_type __s = default_seed)
{seed(integral_constant<bool, __m == 0>(),
integral_constant<bool, __c == 0>(), __s);}
template<class _Sseq>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
__is_seed_sequence<_Sseq, linear_congruential_engine>::value,
void
>::type
seed(_Sseq& __q)
{__seed(__q, integral_constant<unsigned,
1 + (__m == 0 ? (sizeof(result_type) * __CHAR_BIT__ - 1)/32
: (__m > 0x100000000ull))>());}
// generating functions
_LIBCPP_INLINE_VISIBILITY
result_type operator()()
{return __x_ = static_cast<result_type>(__lce_ta<__a, __c, __m, _Mp>::next(__x_));}
_LIBCPP_INLINE_VISIBILITY
void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
friend _LIBCPP_INLINE_VISIBILITY
bool operator==(const linear_congruential_engine& __x,
const linear_congruential_engine& __y)
{return __x.__x_ == __y.__x_;}
friend _LIBCPP_INLINE_VISIBILITY
bool operator!=(const linear_congruential_engine& __x,
const linear_congruential_engine& __y)
{return !(__x == __y);}
private:
_LIBCPP_INLINE_VISIBILITY
void seed(true_type, true_type, result_type __s) {__x_ = __s == 0 ? 1 : __s;}
_LIBCPP_INLINE_VISIBILITY
void seed(true_type, false_type, result_type __s) {__x_ = __s;}
_LIBCPP_INLINE_VISIBILITY
void seed(false_type, true_type, result_type __s) {__x_ = __s % __m == 0 ?
1 : __s % __m;}
_LIBCPP_INLINE_VISIBILITY
void seed(false_type, false_type, result_type __s) {__x_ = __s % __m;}
template<class _Sseq>
void __seed(_Sseq& __q, integral_constant<unsigned, 1>);
template<class _Sseq>
void __seed(_Sseq& __q, integral_constant<unsigned, 2>);
template <class _CharT, class _Traits,
class _Up, _Up _Ap, _Up _Cp, _Up _Np>
friend
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const linear_congruential_engine<_Up, _Ap, _Cp, _Np>&);
template <class _CharT, class _Traits,
class _Up, _Up _Ap, _Up _Cp, _Up _Np>
friend
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
linear_congruential_engine<_Up, _Ap, _Cp, _Np>& __x);
};
template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
_LIBCPP_CONSTEXPR const typename linear_congruential_engine<_UIntType, __a, __c, __m>::result_type
linear_congruential_engine<_UIntType, __a, __c, __m>::multiplier;
template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
_LIBCPP_CONSTEXPR const typename linear_congruential_engine<_UIntType, __a, __c, __m>::result_type
linear_congruential_engine<_UIntType, __a, __c, __m>::increment;
template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
_LIBCPP_CONSTEXPR const typename linear_congruential_engine<_UIntType, __a, __c, __m>::result_type
linear_congruential_engine<_UIntType, __a, __c, __m>::modulus;
template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
_LIBCPP_CONSTEXPR const typename linear_congruential_engine<_UIntType, __a, __c, __m>::result_type
linear_congruential_engine<_UIntType, __a, __c, __m>::default_seed;
template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
template<class _Sseq>
void
linear_congruential_engine<_UIntType, __a, __c, __m>::__seed(_Sseq& __q,
integral_constant<unsigned, 1>)
{
const unsigned __k = 1;
uint32_t __ar[__k+3];
__q.generate(__ar, __ar + __k + 3);
result_type __s = static_cast<result_type>(__ar[3] % __m);
__x_ = __c == 0 && __s == 0 ? result_type(1) : __s;
}
template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
template<class _Sseq>
void
linear_congruential_engine<_UIntType, __a, __c, __m>::__seed(_Sseq& __q,
integral_constant<unsigned, 2>)
{
const unsigned __k = 2;
uint32_t __ar[__k+3];
__q.generate(__ar, __ar + __k + 3);
result_type __s = static_cast<result_type>((__ar[3] +
((uint64_t)__ar[4] << 32)) % __m);
__x_ = __c == 0 && __s == 0 ? result_type(1) : __s;
}
template <class _CharT, class _Traits,
class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
inline _LIBCPP_INLINE_VISIBILITY
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const linear_congruential_engine<_UIntType, __a, __c, __m>& __x)
{
__save_flags<_CharT, _Traits> __lx(__os);
typedef basic_ostream<_CharT, _Traits> _Ostream;
__os.flags(_Ostream::dec | _Ostream::left);
__os.fill(__os.widen(' '));
return __os << __x.__x_;
}
template <class _CharT, class _Traits,
class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
linear_congruential_engine<_UIntType, __a, __c, __m>& __x)
{
__save_flags<_CharT, _Traits> __lx(__is);
typedef basic_istream<_CharT, _Traits> _Istream;
__is.flags(_Istream::dec | _Istream::skipws);
_UIntType __t;
__is >> __t;
if (!__is.fail())
__x.__x_ = __t;
return __is;
}
typedef linear_congruential_engine<uint_fast32_t, 16807, 0, 2147483647>
minstd_rand0;
typedef linear_congruential_engine<uint_fast32_t, 48271, 0, 2147483647>
minstd_rand;
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___RANDOM_LINEAR_CONGRUENTIAL_ENGINE_H
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