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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