368faacac7
This commit reverts 5aaefa51 (and also partly 7f285f48e77 and b6d75682f9, which were related to the original commit). As landed, 5aaefa51 had unintended consequences on some downstream bots and didn't have proper coverage upstream due to a few subtle things. Implementing this is something we should do in libc++, however we'll first need to address a few issues listed in https://reviews.llvm.org/D106124#3349710. Differential Revision: https://reviews.llvm.org/D120683
54 lines
1.6 KiB
C++
54 lines
1.6 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___RANDOM_GENERATE_CANONICAL_H
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#define _LIBCPP___RANDOM_GENERATE_CANONICAL_H
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#include <__config>
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#include <__random/log2.h>
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#include <cstdint>
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#include <initializer_list>
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#include <limits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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// generate_canonical
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template<class _RealType, size_t __bits, class _URNG>
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_RealType
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generate_canonical(_URNG& __g)
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{
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const size_t _Dt = numeric_limits<_RealType>::digits;
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const size_t __b = _Dt < __bits ? _Dt : __bits;
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#ifdef _LIBCPP_CXX03_LANG
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const size_t __logR = __log2<uint64_t, _URNG::_Max - _URNG::_Min + uint64_t(1)>::value;
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#else
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const size_t __logR = __log2<uint64_t, _URNG::max() - _URNG::min() + uint64_t(1)>::value;
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#endif
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const size_t __k = __b / __logR + (__b % __logR != 0) + (__b == 0);
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const _RealType _Rp = static_cast<_RealType>(_URNG::max() - _URNG::min()) + _RealType(1);
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_RealType __base = _Rp;
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_RealType _Sp = __g() - _URNG::min();
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for (size_t __i = 1; __i < __k; ++__i, __base *= _Rp)
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_Sp += (__g() - _URNG::min()) * __base;
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return _Sp / __base;
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}
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___RANDOM_GENERATE_CANONICAL_H
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