1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___RANDOM_GENERATE_CANONICAL_H 10 #define _LIBCPP___RANDOM_GENERATE_CANONICAL_H 11 12 #include <__config> 13 #include <__random/log2.h> 14 #include <cstdint> 15 #include <initializer_list> 16 #include <limits> 17 18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 19 # pragma GCC system_header 20 #endif 21 22 _LIBCPP_PUSH_MACROS 23 #include <__undef_macros> 24 25 _LIBCPP_BEGIN_NAMESPACE_STD 26 27 // generate_canonical 28 29 template<class _RealType, size_t __bits, class _URNG> 30 _LIBCPP_HIDE_FROM_ABI _RealType 31 generate_canonical(_URNG& __g) 32 { 33 const size_t _Dt = numeric_limits<_RealType>::digits; 34 const size_t __b = _Dt < __bits ? _Dt : __bits; 35 #ifdef _LIBCPP_CXX03_LANG 36 const size_t __logR = __log2<uint64_t, _URNG::_Max - _URNG::_Min + uint64_t(1)>::value; 37 #else 38 const size_t __logR = __log2<uint64_t, _URNG::max() - _URNG::min() + uint64_t(1)>::value; 39 #endif 40 const size_t __k = __b / __logR + (__b % __logR != 0) + (__b == 0); 41 const _RealType _Rp = static_cast<_RealType>(_URNG::max() - _URNG::min()) + _RealType(1); 42 _RealType __base = _Rp; 43 _RealType _Sp = __g() - _URNG::min(); 44 for (size_t __i = 1; __i < __k; ++__i, __base *= _Rp) 45 _Sp += (__g() - _URNG::min()) * __base; 46 return _Sp / __base; 47 } 48 49 _LIBCPP_END_NAMESPACE_STD 50 51 _LIBCPP_POP_MACROS 52 53 #endif // _LIBCPP___RANDOM_GENERATE_CANONICAL_H 54