Comprehensive C++ Hashmap Benchmarks (2022)

3 comments

• spacechild1 25 minutes ago
  Note that this benchmark does not include boost::unordered_flat_map. This is an open addressing variant of boost::unordered_map which has only been released in December 2022.

  I wanted to mention this because boost::unordered_flat_map and boost::unordered_flat_set are among the fastest open addressing hash containers in C++ land. Internally, they use lots of cool SIMD tricks. If anyone is interested in the details, here's a nice blog post by the developer: https://bannalia.blogspot.com/2022/11/inside-boostunorderedf...
• hermitcrab 50 minutes ago
  Would be interested to hear how the Qt QHash compares.

  https://doc.qt.io/qt-6/qhash.html

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  • rurban 30 minutes ago
    Still using linked lists as std::unordered_map. So it won't fly, but keeps ptr stability.
• rurban 32 minutes ago
  Not really comprehesive. Doesn't include my favorite https://github.com/greg7mdp/parallel-hashmap which adds thread-safety to performance.
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  • aw1621107 28 minutes ago
    For what it's worth, there's this bit from the parallel-hashmap readme:

    > We encourage phmap users to switch to gtl if possible. gtl provides the same functionality as this repository, but requires C++20 or above.

    And the benchmarks do include gtl.