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cosmopolitan/third_party/libcxx/__random/linear_congruential_engine.h
Justine Tunney 5660ec4741
Release Cosmopolitan v3.6.0 
This release is an atomic upgrade to GCC 14.1.0 with C23 and C++23
2024-07-23 03:28:19 -07:00

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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 <__type_traits/enable_if.h>
#include <__type_traits/integral_constant.h>
#include <__type_traits/is_unsigned.h>
#include <cstdint>
#include <iosfwd>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
enum __lce_alg_type {
_LCE_Full,
_LCE_Part,
_LCE_Schrage,
_LCE_Promote,
};
template <unsigned long long __a,
unsigned long long __c,
unsigned long long __m,
unsigned long long _Mp,
bool _HasOverflow = (__a != 0ull && (__m & (__m - 1ull)) != 0ull), // a != 0, m != 0, m != 2^n
bool _Full = (!_HasOverflow || __m - 1ull <= (_Mp - __c) / __a), // (a * x + c) % m works
bool _Part = (!_HasOverflow || __m - 1ull <= _Mp / __a), // (a * x) % m works
bool _Schrage = (_HasOverflow && __m % __a <= __m / __a)> // r <= q
struct __lce_alg_picker {
static _LIBCPP_CONSTEXPR const __lce_alg_type __mode =
_Full ? _LCE_Full
: _Part ? _LCE_Part
: _Schrage ? _LCE_Schrage
: _LCE_Promote;
#ifdef _LIBCPP_HAS_NO_INT128
static_assert(_Mp != (unsigned long long)(-1) || _Full || _Part || _Schrage,
"The current values for a, c, and m are not currently supported on platforms without __int128");
#endif
};
template <unsigned long long __a,
unsigned long long __c,
unsigned long long __m,
unsigned long long _Mp,
__lce_alg_type _Mode = __lce_alg_picker<__a, __c, __m, _Mp>::__mode>
struct __lce_ta;
// 64
#ifndef _LIBCPP_HAS_NO_INT128
template <unsigned long long _Ap, unsigned long long _Cp, unsigned long long _Mp>
struct __lce_ta<_Ap, _Cp, _Mp, (unsigned long long)(-1), _LCE_Promote> {
typedef unsigned long long result_type;
_LIBCPP_HIDE_FROM_ABI static result_type next(result_type __xp) {
__extension__ using __calc_type = unsigned __int128;
const __calc_type __a = static_cast<__calc_type>(_Ap);
const __calc_type __c = static_cast<__calc_type>(_Cp);
const __calc_type __m = static_cast<__calc_type>(_Mp);
const __calc_type __x = static_cast<__calc_type>(__xp);
return static_cast<result_type>((__a * __x + __c) % __m);
}
};
#endif
template <unsigned long long __a, unsigned long long __c, unsigned long long __m>
struct __lce_ta<__a, __c, __m, (unsigned long long)(-1), _LCE_Schrage> {
typedef unsigned long long result_type;
_LIBCPP_HIDE_FROM_ABI 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, 0ull, __m, (unsigned long long)(-1), _LCE_Schrage> {
typedef unsigned long long result_type;
_LIBCPP_HIDE_FROM_ABI 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)(-1), _LCE_Part> {
typedef unsigned long long result_type;
_LIBCPP_HIDE_FROM_ABI static result_type next(result_type __x) {
// Use (((a*x) % m) + c) % m
__x = (__a * __x) % __m;
__x += __c - (__x >= __m - __c) * __m;
return __x;
}
};
template <unsigned long long __a, unsigned long long __c, unsigned long long __m>
struct __lce_ta<__a, __c, __m, (unsigned long long)(-1), _LCE_Full> {
typedef unsigned long long result_type;
_LIBCPP_HIDE_FROM_ABI 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, 0ull, (unsigned long long)(-1), _LCE_Full> {
typedef unsigned long long result_type;
_LIBCPP_HIDE_FROM_ABI static result_type next(result_type __x) { return __a * __x + __c; }
};
// 32
template <unsigned long long __a, unsigned long long __c, unsigned long long __m>
struct __lce_ta<__a, __c, __m, unsigned(-1), _LCE_Promote> {
typedef unsigned result_type;
_LIBCPP_HIDE_FROM_ABI static result_type next(result_type __x) {
return static_cast<result_type>(__lce_ta<__a, __c, __m, (unsigned long long)(-1)>::next(__x));
}
};
template <unsigned long long _Ap, unsigned long long _Cp, unsigned long long _Mp>
struct __lce_ta<_Ap, _Cp, _Mp, unsigned(-1), _LCE_Schrage> {
typedef unsigned result_type;
_LIBCPP_HIDE_FROM_ABI 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, 0ull, _Mp, unsigned(-1), _LCE_Schrage> {
typedef unsigned result_type;
_LIBCPP_HIDE_FROM_ABI 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(-1), _LCE_Part> {
typedef unsigned result_type;
_LIBCPP_HIDE_FROM_ABI 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);
// Use (((a*x) % m) + c) % m
__x = (__a * __x) % __m;
__x += __c - (__x >= __m - __c) * __m;
return __x;
}
};
template <unsigned long long _Ap, unsigned long long _Cp, unsigned long long _Mp>
struct __lce_ta<_Ap, _Cp, _Mp, unsigned(-1), _LCE_Full> {
typedef unsigned result_type;
_LIBCPP_HIDE_FROM_ABI 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, 0ull, unsigned(-1), _LCE_Full> {
typedef unsigned result_type;
_LIBCPP_HIDE_FROM_ABI 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, __lce_alg_type __mode>
struct __lce_ta<__a, __c, __m, (unsigned short)(-1), __mode> {
typedef unsigned short result_type;
_LIBCPP_HIDE_FROM_ABI static result_type next(result_type __x) {
return static_cast<result_type>(__lce_ta<__a, __c, __m, unsigned(-1)>::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_HIDE_FROM_ABI 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>
_LIBCPP_HIDE_FROM_ABI 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(-1);
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 - _UIntType(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_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type min() { return _Min; }
_LIBCPP_HIDE_FROM_ABI 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_HIDE_FROM_ABI linear_congruential_engine() : linear_congruential_engine(default_seed) {}
_LIBCPP_HIDE_FROM_ABI explicit linear_congruential_engine(result_type __s) { seed(__s); }
#else
_LIBCPP_HIDE_FROM_ABI explicit linear_congruential_engine(result_type __s = default_seed) { seed(__s); }
#endif
template <class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, linear_congruential_engine>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI explicit linear_congruential_engine(_Sseq& __q) {
seed(__q);
}
_LIBCPP_HIDE_FROM_ABI void seed(result_type __s = default_seed) {
seed(integral_constant<bool, __m == 0>(), integral_constant<bool, __c == 0>(), __s);
}
template <class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, linear_congruential_engine>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI void seed(_Sseq& __q) {
__seed(
__q,
integral_constant<unsigned,
1 + (__m == 0 ? (sizeof(result_type) * __CHAR_BIT__ - 1) / 32 : (__m > 0x100000000ull))>());
}
// generating functions
_LIBCPP_HIDE_FROM_ABI result_type operator()() {
return __x_ = static_cast<result_type>(__lce_ta<__a, __c, __m, _Mp>::next(__x_));
}
_LIBCPP_HIDE_FROM_ABI void discard(unsigned long long __z) {
for (; __z; --__z)
operator()();
}
friend _LIBCPP_HIDE_FROM_ABI bool
operator==(const linear_congruential_engine& __x, const linear_congruential_engine& __y) {
return __x.__x_ == __y.__x_;
}
friend _LIBCPP_HIDE_FROM_ABI bool
operator!=(const linear_congruential_engine& __x, const linear_congruential_engine& __y) {
return !(__x == __y);
}
private:
_LIBCPP_HIDE_FROM_ABI void seed(true_type, true_type, result_type __s) { __x_ = __s == 0 ? 1 : __s; }
_LIBCPP_HIDE_FROM_ABI void seed(true_type, false_type, result_type __s) { __x_ = __s; }
_LIBCPP_HIDE_FROM_ABI void seed(false_type, true_type, result_type __s) { __x_ = __s % __m == 0 ? 1 : __s % __m; }
_LIBCPP_HIDE_FROM_ABI void seed(false_type, false_type, result_type __s) { __x_ = __s % __m; }
template <class _Sseq>
_LIBCPP_HIDE_FROM_ABI void __seed(_Sseq& __q, integral_constant<unsigned, 1>);
template <class _Sseq>
_LIBCPP_HIDE_FROM_ABI 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_HIDE_FROM_ABI 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>
_LIBCPP_HIDE_FROM_ABI 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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