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Better 64-bit hash_combine

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This commit is contained in:
Nikita Lisitsa 2021-04-25 22:08:42 +03:00
parent bcc908d064
commit f9894647e3
1 changed files with 6 additions and 2 deletions
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8
libs/util/include/psemek/util/hash.hpp
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@ -6,10 +6,14 @@
namespace psemek::util namespace psemek::util
{ {
// based on boost::hash_combine
inline void hash_combine(std::size_t & seed, std::size_t value) inline void hash_combine(std::size_t & seed, std::size_t value)
{ {
seed ^= value + 0x9e3779b9 + (seed<<6) + (seed>>2); static const std::size_t k = 0x9ddfea08eb382d69ULL;
std::size_t a = (value ^ seed) * k;
a ^= (a >> 47);
std::size_t b = (seed ^ a) * k;
b ^= (b >> 47);
seed = b * k;
} }
} }