e4eccd6a3c
Instead of just calling the single element `erase` on every element of the range, we can combine some of the operations in a custom implementation. Specifically, we don't need to search for the previous node or re-link the list every iteration. Removing this unnecessary work results in some nice performance improvements: ``` ----------------------------------------------------------------------------------------------------------------------- Benchmark old new ----------------------------------------------------------------------------------------------------------------------- std::unordered_set<int>::erase(iterator, iterator) (erase half the container)/0 457 ns 459 ns std::unordered_set<int>::erase(iterator, iterator) (erase half the container)/32 995 ns 626 ns std::unordered_set<int>::erase(iterator, iterator) (erase half the container)/1024 18196 ns 7995 ns std::unordered_set<int>::erase(iterator, iterator) (erase half the container)/8192 124722 ns 70125 ns std::unordered_set<std::string>::erase(iterator, iterator) (erase half the container)/0 456 ns 461 ns std::unordered_set<std::string>::erase(iterator, iterator) (erase half the container)/32 1183 ns 769 ns std::unordered_set<std::string>::erase(iterator, iterator) (erase half the container)/1024 27827 ns 18614 ns std::unordered_set<std::string>::erase(iterator, iterator) (erase half the container)/8192 266681 ns 226107 ns std::unordered_map<int, int>::erase(iterator, iterator) (erase half the container)/0 455 ns 462 ns std::unordered_map<int, int>::erase(iterator, iterator) (erase half the container)/32 996 ns 659 ns std::unordered_map<int, int>::erase(iterator, iterator) (erase half the container)/1024 15963 ns 8108 ns std::unordered_map<int, int>::erase(iterator, iterator) (erase half the container)/8192 136493 ns 71848 ns std::unordered_multiset<int>::erase(iterator, iterator) (erase half the container)/0 454 ns 455 ns std::unordered_multiset<int>::erase(iterator, iterator) (erase half the container)/32 985 ns 703 ns std::unordered_multiset<int>::erase(iterator, iterator) (erase half the container)/1024 16277 ns 9085 ns std::unordered_multiset<int>::erase(iterator, iterator) (erase half the container)/8192 125736 ns 82710 ns std::unordered_multimap<int, int>::erase(iterator, iterator) (erase half the container)/0 457 ns 454 ns std::unordered_multimap<int, int>::erase(iterator, iterator) (erase half the container)/32 1091 ns 646 ns std::unordered_multimap<int, int>::erase(iterator, iterator) (erase half the container)/1024 17784 ns 7664 ns std::unordered_multimap<int, int>::erase(iterator, iterator) (erase half the container)/8192 127098 ns 72806 ns ```
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