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[Zerocoin][Validation] Cache checksum heights
Validating zerocoin spends requires determining the height of an accumulator hash, which is done by searching through all the blocks in the chain starting from genesis, for every txin. Since the height of a particular hash-denomination pair is not going to change, we can cache it. This is most useful for in-wallet block template generation, since each mining thread performs these validations separately (while holding cs_main). Adds a SimpleLRUCache template based on 7c9e97a and uses it to store checksum heights. I chose a particular size for it that should be large enough for significant spends. This results in a roughly 30+x speedup of zerocoin spend validation (26-30ms/txin -> 0.4-0.9ms/txin). Vastly improves #862 alongside #915.
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| // Copyright (c) 2021 Veil developers | ||
| // Distributed under the MIT software license, see the accompanying | ||
| // file COPYING or http://www.opensource.org/licenses/mit-license.php. | ||
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| #ifndef VEIL_LRU_CACHE_H | ||
| #define VEIL_LRU_CACHE_H | ||
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| #include "sync.h" | ||
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| #include <list> | ||
| #include <unordered_map> | ||
| #include <utility> | ||
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| namespace veil { | ||
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| /** | ||
| * The SimpleLRUCache is a fixed-size key-value map that automatically | ||
| * evicts the least-recently-used item when a new item is added while the cache is full. | ||
| * | ||
| * This is a naive, non-optimized implementation of an LRU cache that uses an | ||
| * internal mutex to prevent concurrent access. | ||
| * | ||
| * K must be a hashable type, but you can define your own Hash for it, or equivalently implement | ||
| * std::hash<K> for your type. It must be a default-constructible struct or class | ||
| * defining std::size_t operator()(const K&) const, e.g. | ||
| * | ||
| * namespace std { | ||
| * template<> struct hash<MyType> | ||
| * { | ||
| * std::size_t operator()(const MyType& m) const { | ||
| * return std::hash<std::string>()(m.ImportantString()) ^ m.ImportantInteger; | ||
| * } | ||
| * }; | ||
| * } | ||
| * SimpleLRUCache<MyType, MyValue> cache(100); | ||
| */ | ||
| template<typename K, typename V = K, class Hash = std::hash<K>> | ||
| class SimpleLRUCache | ||
| { | ||
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| private: | ||
| std::list<K> items; | ||
| std::unordered_map<K, std::pair<V, typename std::list<K>::iterator>, Hash> keyValuesMap; | ||
| int csize; | ||
| CCriticalSection cs_mycache; | ||
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| public: | ||
| SimpleLRUCache(int s) : csize(s < 1 ? 10 : s), keyValuesMap(csize) {} | ||
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| void set(const K key, const V value) { | ||
| LOCK(cs_mycache); | ||
| auto pos = keyValuesMap.find(key); | ||
| if (pos == keyValuesMap.end()) { | ||
| items.push_front(key); | ||
| keyValuesMap[key] = { value, items.begin() }; | ||
| if (keyValuesMap.size() > csize) { | ||
| keyValuesMap.erase(items.back()); | ||
| items.pop_back(); | ||
| } | ||
| } else { | ||
| items.erase(pos->second.second); | ||
| items.push_front(key); | ||
| keyValuesMap[key] = { value, items.begin() }; | ||
| } | ||
| } | ||
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| bool get(const K key, V &value) { | ||
| LOCK(cs_mycache); | ||
| auto pos = keyValuesMap.find(key); | ||
| if (pos == keyValuesMap.end()) | ||
| return false; | ||
| items.erase(pos->second.second); | ||
| items.push_front(key); | ||
| keyValuesMap[key] = { pos->second.first, items.begin() }; | ||
| value = pos->second.first; | ||
| return true; | ||
| } | ||
| }; | ||
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| } // namespace veil | ||
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| #endif // VEIL_LRU_CACHE_H |
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