Allow non-power-of-2 signature cache sizes
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02e5308c1b
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7482781347
1 changed files with 11 additions and 18 deletions
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@ -154,7 +154,7 @@ public:
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* @tparam Element should be a movable and copyable type
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* @tparam Hash should be a function/callable which takes a template parameter
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* hash_select and an Element and extracts a hash from it. Should return
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* high-entropy hashes for `Hash h; h<0>(e) ... h<7>(e)`.
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* high-entropy uint32_t hashes for `Hash h; h<0>(e) ... h<7>(e)`.
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*/
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template <typename Element, typename Hash>
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class cache
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@ -193,12 +193,6 @@ private:
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*/
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uint32_t epoch_size;
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/** hash_mask should be set to appropriately mask out a hash such that every
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* masked hash is [0,size), eg, if floor(log2(size)) == 20, then hash_mask
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* should be (1<<20)-1
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*/
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uint32_t hash_mask;
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/** depth_limit determines how many elements insert should try to replace.
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* Should be set to log2(n)*/
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uint8_t depth_limit;
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@ -217,14 +211,14 @@ private:
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*/
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inline std::array<uint32_t, 8> compute_hashes(const Element& e) const
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{
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return {{hash_function.template operator()<0>(e) & hash_mask,
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hash_function.template operator()<1>(e) & hash_mask,
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hash_function.template operator()<2>(e) & hash_mask,
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hash_function.template operator()<3>(e) & hash_mask,
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hash_function.template operator()<4>(e) & hash_mask,
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hash_function.template operator()<5>(e) & hash_mask,
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hash_function.template operator()<6>(e) & hash_mask,
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hash_function.template operator()<7>(e) & hash_mask}};
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return {{(uint32_t)((hash_function.template operator()<0>(e) * (uint64_t)size) >> 32),
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(uint32_t)((hash_function.template operator()<1>(e) * (uint64_t)size) >> 32),
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(uint32_t)((hash_function.template operator()<2>(e) * (uint64_t)size) >> 32),
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(uint32_t)((hash_function.template operator()<3>(e) * (uint64_t)size) >> 32),
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(uint32_t)((hash_function.template operator()<4>(e) * (uint64_t)size) >> 32),
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(uint32_t)((hash_function.template operator()<5>(e) * (uint64_t)size) >> 32),
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(uint32_t)((hash_function.template operator()<6>(e) * (uint64_t)size) >> 32),
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(uint32_t)((hash_function.template operator()<7>(e) * (uint64_t)size) >> 32)}};
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}
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/* end
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@ -305,7 +299,7 @@ public:
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}
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/** setup initializes the container to store no more than new_size
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* elements. setup rounds down to a power of two size.
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* elements.
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*
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* setup should only be called once.
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*
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@ -316,8 +310,7 @@ public:
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{
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// depth_limit must be at least one otherwise errors can occur.
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depth_limit = static_cast<uint8_t>(std::log2(static_cast<float>(std::max((uint32_t)2, new_size))));
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size = 1 << depth_limit;
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hash_mask = size-1;
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size = std::max<uint32_t>(2, new_size);
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table.resize(size);
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collection_flags.setup(size);
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epoch_flags.resize(size);
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