243 lines
6.6 KiB
C++
Executable File
243 lines
6.6 KiB
C++
Executable File
/////////////////////////////////////////////////////////////////////////////
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//
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// (C) Copyright Ion Gaztanaga 2014-2014
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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// See http://www.boost.org/libs/intrusive for documentation.
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//
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/////////////////////////////////////////////////////////////////////////////
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#ifndef BOOST_INTRUSIVE_DETAIL_MATH_HPP
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#define BOOST_INTRUSIVE_DETAIL_MATH_HPP
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#ifndef BOOST_CONFIG_HPP
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# include <boost/config.hpp>
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#endif
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#if defined(BOOST_HAS_PRAGMA_ONCE)
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# pragma once
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#endif
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#include <cstddef>
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#include <climits>
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#include <boost/intrusive/detail/mpl.hpp>
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#include <cstring>
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namespace boost {
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namespace intrusive {
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namespace detail {
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///////////////////////////
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// floor_log2 Dispatcher
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////////////////////////////
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#if defined(_MSC_VER) && (_MSC_VER >= 1300)
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}}} //namespace boost::intrusive::detail
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//Use _BitScanReverseXX intrinsics
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#if defined(_M_X64) || defined(_M_AMD64) || defined(_M_IA64) //64 bit target
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#define BOOST_INTRUSIVE_BSR_INTRINSIC_64_BIT
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#endif
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#ifndef __INTRIN_H_ // Avoid including any windows system header
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#ifdef __cplusplus
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extern "C" {
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#endif // __cplusplus
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#if defined(BOOST_INTRUSIVE_BSR_INTRINSIC_64_BIT) //64 bit target
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unsigned char _BitScanReverse64(unsigned long *index, unsigned __int64 mask);
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#pragma intrinsic(_BitScanReverse64)
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#else //32 bit target
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unsigned char _BitScanReverse(unsigned long *index, unsigned long mask);
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#pragma intrinsic(_BitScanReverse)
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#endif
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#ifdef __cplusplus
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}
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#endif // __cplusplus
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#endif // __INTRIN_H_
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#ifdef BOOST_INTRUSIVE_BSR_INTRINSIC_64_BIT
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#define BOOST_INTRUSIVE_BSR_INTRINSIC _BitScanReverse64
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#undef BOOST_INTRUSIVE_BSR_INTRINSIC_64_BIT
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#else
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#define BOOST_INTRUSIVE_BSR_INTRINSIC _BitScanReverse
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#endif
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namespace boost {
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namespace intrusive {
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namespace detail {
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inline std::size_t floor_log2 (std::size_t x)
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{
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unsigned long log2;
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BOOST_INTRUSIVE_BSR_INTRINSIC( &log2, x );
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return static_cast<std::size_t>(log2);
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}
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#undef BOOST_INTRUSIVE_BSR_INTRINSIC
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#elif defined(__GNUC__) && ((__GNUC__ >= 4) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)) //GCC >=3.4
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//Compile-time error in case of missing specialization
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template<class Uint>
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struct builtin_clz_dispatch;
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#if defined(BOOST_HAS_LONG_LONG)
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template<>
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struct builtin_clz_dispatch< ::boost::ulong_long_type >
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{
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static ::boost::ulong_long_type call(::boost::ulong_long_type n)
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{ return (::boost::ulong_long_type)__builtin_clzll(n); }
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};
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#endif
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template<>
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struct builtin_clz_dispatch<unsigned long>
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{
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static unsigned long call(unsigned long n)
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{ return (unsigned long)__builtin_clzl(n); }
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};
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template<>
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struct builtin_clz_dispatch<unsigned int>
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{
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static unsigned int call(unsigned int n)
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{ return (unsigned int)__builtin_clz(n); }
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};
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inline std::size_t floor_log2(std::size_t n)
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{
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return sizeof(std::size_t)*CHAR_BIT - std::size_t(1) - builtin_clz_dispatch<std::size_t>::call(n);
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}
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#else //Portable methods
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////////////////////////////
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// Generic method
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////////////////////////////
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inline std::size_t floor_log2_get_shift(std::size_t n, true_ )//power of two size_t
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{ return n >> 1; }
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inline std::size_t floor_log2_get_shift(std::size_t n, false_ )//non-power of two size_t
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{ return (n >> 1) + ((n & 1u) & (n != 1)); }
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template<std::size_t N>
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inline std::size_t floor_log2 (std::size_t x, integral_constant<std::size_t, N>)
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{
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const std::size_t Bits = N;
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const bool Size_t_Bits_Power_2= !(Bits & (Bits-1));
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std::size_t n = x;
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std::size_t log2 = 0;
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std::size_t remaining_bits = Bits;
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std::size_t shift = floor_log2_get_shift(remaining_bits, bool_<Size_t_Bits_Power_2>());
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while(shift){
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std::size_t tmp = n >> shift;
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if (tmp){
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log2 += shift, n = tmp;
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}
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shift = floor_log2_get_shift(shift, bool_<Size_t_Bits_Power_2>());
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}
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return log2;
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}
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inline std::size_t floor_log2 (std::size_t x)
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{
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const std::size_t Bits = sizeof(std::size_t)*CHAR_BIT;
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return floor_log2(x, integral_constant<std::size_t, Bits>());
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}
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#endif
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//Thanks to Laurent de Soras in
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//http://www.flipcode.com/archives/Fast_log_Function.shtml
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inline float fast_log2 (float val)
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{
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unsigned x;
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std::memcpy(&x, &val, sizeof(float));
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const int log_2 = int((x >> 23) & 255) - 128;
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x &= ~(unsigned(255u) << 23u);
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x += unsigned(127) << 23u;
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std::memcpy(&val, &x, sizeof(float));
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//1+log2(m), m ranging from 1 to 2
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//3rd degree polynomial keeping first derivate continuity.
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//For less precision the line can be commented out
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val = ((-1.f/3.f) * val + 2.f) * val - (2.f/3.f);
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return val + static_cast<float>(log_2);
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}
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inline bool is_pow2(std::size_t x)
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{ return (x & (x-1)) == 0; }
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template<std::size_t N>
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struct static_is_pow2
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{
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static const bool value = (N & (N-1)) == 0;
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};
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inline std::size_t ceil_log2 (std::size_t x)
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{
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return static_cast<std::size_t>(!(is_pow2)(x)) + floor_log2(x);
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}
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inline std::size_t ceil_pow2 (std::size_t x)
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{
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return std::size_t(1u) << (ceil_log2)(x);
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}
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inline std::size_t previous_or_equal_pow2(std::size_t x)
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{
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return std::size_t(1u) << floor_log2(x);
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}
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template<class SizeType, std::size_t N>
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struct numbits_eq
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{
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static const bool value = sizeof(SizeType)*CHAR_BIT == N;
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};
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template<class SizeType, class Enabler = void >
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struct sqrt2_pow_max;
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template <class SizeType>
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struct sqrt2_pow_max<SizeType, typename voider<typename enable_if< numbits_eq<SizeType, 32> >::type>::type>
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{
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static const SizeType value = 0xb504f334;
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static const std::size_t pow = 31;
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};
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#ifndef BOOST_NO_INT64_T
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template <class SizeType>
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struct sqrt2_pow_max<SizeType, typename voider<typename enable_if< numbits_eq<SizeType, 64> >::type>::type>
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{
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static const SizeType value = 0xb504f333f9de6484ull;
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static const std::size_t pow = 63;
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};
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#endif //BOOST_NO_INT64_T
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// Returns floor(pow(sqrt(2), x * 2 + 1)).
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// Defined for X from 0 up to the number of bits in size_t minus 1.
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inline std::size_t sqrt2_pow_2xplus1 (std::size_t x)
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{
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const std::size_t value = (std::size_t)sqrt2_pow_max<std::size_t>::value;
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const std::size_t pow = (std::size_t)sqrt2_pow_max<std::size_t>::pow;
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return (value >> (pow - x)) + 1;
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}
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} //namespace detail
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} //namespace intrusive
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} //namespace boost
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#endif //BOOST_INTRUSIVE_DETAIL_MATH_HPP
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