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 generate_canonical(_URNG& __g) { 31 const size_t __dt = numeric_limits<_RealType>::digits; 32 const size_t __b = __dt < __bits ? __dt : __bits; 33 #ifdef _LIBCPP_CXX03_LANG 34 const size_t __log_r = __log2<uint64_t, _URNG::_Max - _URNG::_Min + uint64_t(1)>::value; 35 #else 36 const size_t __log_r = __log2<uint64_t, _URNG::max() - _URNG::min() + uint64_t(1)>::value; 37 #endif 38 const size_t __k = __b / __log_r + (__b % __log_r != 0) + (__b == 0); 39 const _RealType __rp = static_cast<_RealType>(_URNG::max() - _URNG::min()) + _RealType(1); 40 _RealType __base = __rp; 41 _RealType __sp = __g() - _URNG::min(); 42 for (size_t __i = 1; __i < __k; ++__i, __base *= __rp) 43 __sp += (__g() - _URNG::min()) * __base; 44 return __sp / __base; 45 } 46 47 _LIBCPP_END_NAMESPACE_STD 48 49 _LIBCPP_POP_MACROS 50 51 #endif // _LIBCPP___RANDOM_GENERATE_CANONICAL_H 52