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