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20 lines
847 B
C++
20 lines
847 B
C++
#pragma once
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#include <cstdint>
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#include <cstddef>
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/*
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* Author: Konstantin Oblakov
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*
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* Maps random ui64 x (in fact hash of some string) to n baskets/shards.
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* Output value is id of a basket. 0 <= ConsistentHashing(x, n) < n.
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* Probability of all baskets must be equal. Also, it should be consistent
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* in terms, that with different n_1 < n_2 probability of
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* ConsistentHashing(x, n_1) != ConsistentHashing(x, n_2) must be equal to
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* (n_2 - n_1) / n_2 - the least possible with previous conditions.
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* It requires O(1) memory and cpu to calculate. So, it is faster than classic
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* consistent hashing algos with points on circle.
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*/
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std::size_t ConsistentHashing(std::uint64_t x, std::size_t n); // Works good for n < 65536
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std::size_t ConsistentHashing(std::uint64_t lo, std::uint64_t hi, std::size_t n); // Works good for n < 4294967296
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