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fourth attempt

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joaquintides
2022-11-28 17:58:15 +01:00
parent 3a34b8dae9
commit 1e57c08686
1 changed files with 8 additions and 19 deletions
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27
include/boost/unordered/detail/foa.hpp
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@ -689,46 +689,35 @@ struct pow2_size_policy
// of performance // of performance
std::size_t used_bits_=n<=2?1:((std::size_t)(boost::core::bit_width(n-1))); std::size_t used_bits_=n<=2?1:((std::size_t)(boost::core::bit_width(n-1)));
std::size_t used_hi_=used_bits_>=10?(5-(used_bits_%6))*2:0; std::size_t shift_right_=total_bits-used_bits_;
std::size_t used_hi_mask_=(std::size_t(1)<<used_hi_)-1; std::size_t shift_left_=shift_right_%2?0:shift_right_-8;
std::size_t unused_bits_=total_bits-used_bits_;
return (used_hi_mask_<<16)|(used_hi_<<8)|unused_bits_; return (shift_left_<<16)|shift_right_;
} }
static inline std::size_t size(std::size_t size_index_) static inline std::size_t size(std::size_t size_index_)
{ {
return std::size_t(1)<<(total_bits-unused_bits(size_index_)); return std::size_t(1)<<(total_bits-shift_right(size_index_));
} }
static constexpr std::size_t min_size(){return 2;} static constexpr std::size_t min_size(){return 2;}
static inline std::size_t position(std::size_t hash,std::size_t size_index_) static inline std::size_t position(std::size_t hash,std::size_t size_index_)
{ {
std::size_t used_hi_mask_=used_hi_mask(size_index_); return (hash<<shift_left(size_index_))>>shift_right(size_index_);
std::size_t used_hi_=used_hi(size_index_);
std::size_t unused_bits_=unused_bits(size_index_);
hash=boost::core::rotl(hash,(int)used_hi_);
return ((hash>>unused_bits_)&~used_hi_mask_)|(hash&used_hi_mask_);
} }
private: private:
static constexpr std::size_t total_bits=sizeof(std::size_t)*CHAR_BIT; static constexpr std::size_t total_bits=sizeof(std::size_t)*CHAR_BIT;
static inline std::size_t used_hi_mask(std::size_t size_index_) static inline std::size_t shift_left(std::size_t size_index_)
{ {
return size_index_>>16; return size_index_>>16;
} }
static inline std::size_t used_hi(std::size_t size_index_) static inline std::size_t shift_right(std::size_t size_index_)
{ {
return (size_index_>>8)&0xffu; return size_index_&0xffffu;
}
static inline std::size_t unused_bits(std::size_t size_index_)
{
return size_index_&0xffu;
} }
}; };
#endif #endif