63 lines
1.3 KiB
C++
63 lines
1.3 KiB
C++
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#pragma once
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#include "base/logging.hpp"
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#include <cstddef>
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#include <string>
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#include <unordered_map>
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#include <utility>
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namespace search
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{
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template <class Key, class Value>
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class Cache
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{
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std::unordered_map<Key, Value> m_map;
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/// query statistics
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size_t m_accesses;
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size_t m_misses;
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size_t m_emptyQueriesCount; /// empty queries count at a row
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std::string m_name; /// cache name for print functions
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public:
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explicit Cache(std::string const & name) : m_accesses(0), m_misses(0), m_emptyQueriesCount(0), m_name(name) {}
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std::pair<Value &, bool> Get(Key const & key)
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{
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auto r = m_map.insert(std::make_pair(key, Value()));
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++m_accesses;
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if (r.second)
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++m_misses;
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return std::pair<Value &, bool>(r.first->second, r.second);
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}
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void Clear()
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{
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m_map.clear();
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m_accesses = m_misses = 0;
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m_emptyQueriesCount = 0;
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}
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/// Called at the end of every search query.
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void ClearIfNeeded()
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{
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if (m_accesses != 0)
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{
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LOG(LDEBUG,
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("Cache", m_name, "Queries =", m_accesses, "From cache =", m_accesses - m_misses, "Added =", m_misses));
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m_accesses = m_misses = 0;
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m_emptyQueriesCount = 0;
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}
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else if (++m_emptyQueriesCount > 5)
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{
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LOG(LDEBUG, ("Clearing cache", m_name));
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Clear();
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}
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}
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};
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} // namespace search
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