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Simplify hash_value for floating point

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This commit is contained in:
Peter Dimov
2022-09-20 15:01:45 +03:00
parent a426a1939f
commit 8bb7d43646
1 changed files with 11 additions and 64 deletions
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75
include/boost/container_hash/hash.hpp
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@@ -176,12 +176,11 @@ namespace boost
{ {
template<class T, template<class T,
std::size_t Bits = sizeof(T) * CHAR_BIT, std::size_t Bits = sizeof(T) * CHAR_BIT,
int Digits = std::numeric_limits<T>::digits, int Digits = std::numeric_limits<T>::digits>
std::size_t size_t_bits = sizeof(std::size_t) * CHAR_BIT>
struct hash_float_impl; struct hash_float_impl;
// float // float
template<class T, int Digits, std::size_t size_t_bits> struct hash_float_impl<T, 32, Digits, size_t_bits> template<class T, int Digits> struct hash_float_impl<T, 32, Digits>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
@@ -193,35 +192,19 @@ namespace boost
}; };
// double // double
template<class T, int Digits> struct hash_float_impl<T, 64, Digits, 64> template<class T, int Digits> struct hash_float_impl<T, 64, Digits>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
boost::uint64_t w; boost::uint64_t w;
std::memcpy( &w, &v, sizeof( v ) ); std::memcpy( &w, &v, sizeof( v ) );
return w; return hash_value( w );
}
};
template<class T, int Digits> struct hash_float_impl<T, 64, Digits, 32>
{
static std::size_t fn( T v )
{
boost::uint32_t w[ 2 ];
std::memcpy( &w, &v, sizeof( v ) );
std::size_t seed = 0;
seed = static_cast<std::size_t>( w[0] ) + hash_detail::hash_mix( seed );
seed = static_cast<std::size_t>( w[1] ) + hash_detail::hash_mix( seed );
return seed;
} }
}; };
// 80 bit long double in 12 bytes // 80 bit long double in 12 bytes
template<class T> struct hash_float_impl<T, 96, 64, 64> template<class T> struct hash_float_impl<T, 96, 64>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
@@ -230,32 +213,15 @@ namespace boost
std::size_t seed = 0; std::size_t seed = 0;
seed = static_cast<std::size_t>( w[0] ) + hash_detail::hash_mix( seed ); seed = hash_value( w[0] ) + hash_detail::hash_mix( seed );
seed = static_cast<std::size_t>( w[1] ) + hash_detail::hash_mix( seed ); seed = hash_value( w[1] ) + hash_detail::hash_mix( seed );
return seed;
}
};
template<class T> struct hash_float_impl<T, 96, 64, 32>
{
static std::size_t fn( T v )
{
boost::uint32_t w[ 3 ] = {};
std::memcpy( &w, &v, 80 / CHAR_BIT );
std::size_t seed = 0;
seed = static_cast<std::size_t>( w[0] ) + hash_detail::hash_mix( seed );
seed = static_cast<std::size_t>( w[1] ) + hash_detail::hash_mix( seed );
seed = static_cast<std::size_t>( w[2] ) + hash_detail::hash_mix( seed );
return seed; return seed;
} }
}; };
// 80 bit long double in 16 bytes // 80 bit long double in 16 bytes
template<class T> struct hash_float_impl<T, 128, 64, 64> template<class T> struct hash_float_impl<T, 128, 64>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
@@ -264,32 +230,15 @@ namespace boost
std::size_t seed = 0; std::size_t seed = 0;
seed = static_cast<std::size_t>( w[0] ) + hash_detail::hash_mix( seed ); seed = hash_value( w[0] ) + hash_detail::hash_mix( seed );
seed = static_cast<std::size_t>( w[1] ) + hash_detail::hash_mix( seed ); seed = hash_value( w[1] ) + hash_detail::hash_mix( seed );
return seed;
}
};
template<class T> struct hash_float_impl<T, 128, 64, 32>
{
static std::size_t fn( T v )
{
boost::uint32_t w[ 3 ] = {};
std::memcpy( &w, &v, 80 / CHAR_BIT );
std::size_t seed = 0;
seed = static_cast<std::size_t>( w[0] ) + hash_detail::hash_mix( seed );
seed = static_cast<std::size_t>( w[1] ) + hash_detail::hash_mix( seed );
seed = static_cast<std::size_t>( w[2] ) + hash_detail::hash_mix( seed );
return seed; return seed;
} }
}; };
// 128 bit long double // 128 bit long double
template<class T, int Digits, std::size_t size_t_bits> struct hash_float_impl<T, 128, Digits, size_t_bits> template<class T, int Digits> struct hash_float_impl<T, 128, Digits>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
@@ -630,6 +579,4 @@ namespace boost
#endif #endif
} }
#undef BOOST_FUNCTIONAL_HASH_ROTL32
#endif // #ifndef BOOST_FUNCTIONAL_HASH_HASH_HPP #endif // #ifndef BOOST_FUNCTIONAL_HASH_HASH_HPP