Add robin_hood hash set/map containers to 3rdparty
Jonathan G Rennison
1 year ago
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add_files(
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robin_hood.h
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)
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MIT License
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Copyright (c) 2018-2021 Martin Ankerl
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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➵ robin_hood unordered map & set [](https://github.com/martinus/robin-hood-hashing/releases) [](https://raw.githubusercontent.com/martinus/robin-hood-hashing/master/LICENSE)
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============
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------
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> **_NOTE:_** Unfortunately I do not have time to continue development for this hashmap. I have a worthy successor though, please head over to: [`ankerl::unordered_dense::{map, set}`](https://github.com/martinus/unordered_dense)
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> I have spent a lot of time developing and improving it `robin_hood`, and it works quite well for most use cases. I won't make any updates to this code any more, unless they are PRs for critical bug fixes.
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------
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[](https://travis-ci.com/martinus/robin-hood-hashing)
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[](https://ci.appveyor.com/project/martinus/robin-hood-hashing)
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[](https://www.codacy.com/app/martinus/robin-hood-hashing?utm_source=github.com&utm_medium=referral&utm_content=martinus/robin-hood-hashing&utm_campaign=Badge_Grade)
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[](https://lgtm.com/projects/g/martinus/robin-hood-hashing/alerts/)
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[](https://lgtm.com/projects/g/martinus/robin-hood-hashing/context:cpp)
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[](https://coveralls.io/github/martinus/robin-hood-hashing)
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`robin_hood::unordered_map` and `robin_hood::unordered_set` is a platform independent replacement for `std::unordered_map` / `std::unordered_set` which is both faster and more memory efficient for real-world use cases.
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## Installation & Usage
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### Direct Inclusion
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1. Add [`robin_hood.h`](https://github.com/martinus/robin-hood-hashing/releases) to your C++ project.
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1. Use `robin_hood::unordered_map` instead of `std::unordered_map`
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1. Use `robin_hood::unordered_set` instead of `std::unordered_set`
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### [Conan](https://conan.io/), the C/C++ Package Manager
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1. Setup your `CMakeLists.txt` (see [Conan documentation](https://docs.conan.io/en/latest/integrations/build_system.html) on how to use MSBuild, Meson and others) like this:
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```CMake
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project(myproject CXX)
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add_executable(${PROJECT_NAME} main.cpp)
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include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake) # Include Conan-generated file
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conan_basic_setup(TARGETS) # Introduce Conan-generated targets
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target_link_libraries(${PROJECT_NAME} CONAN_PKG::robin-hood-hashing)
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```
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1. Create `conanfile.txt` in your source dir (don't forget to update the version)
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```ini
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[requires]
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robin-hood-hashing/3.11.5
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[generators]
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cmake
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```
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1. Install and run Conan, then build your project as always:
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```Bash
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pip install conan
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mkdir build
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cd build
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conan install ../ --build=missing
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cmake ../
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cmake --build .
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```
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The `robin-hood-hashing` package in Conan is kept up to date by Conan contributors. If the version is out of date, please [create an issue or pull request](https://github.com/conan-io/conan-center-index) on the `conan-center-index` repository.
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## Benchmarks
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Please see extensive benchmarks at [Hashmaps Benchmarks](https://martin.ankerl.com/2019/04/01/hashmap-benchmarks-01-overview/). In short: `robin_hood` is always among the fastest maps and uses far less memory than `std::unordered_map`.
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## Design Choices
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- **Two memory layouts**. Data is either stored in a flat array, or with node indirection. Access for `unordered_flat_map` is extremely fast due to no indirection, but references to elements are not stable. It also causes allocation spikes when the map resizes, and will need plenty of memory for large objects. Node based map has stable references & pointers (NOT iterators! Similar to [std::unordered_map](https://en.cppreference.com/w/cpp/container/unordered_map)) and uses `const Key` in the pair. It is a bit slower due to indirection. The choice is yours; you can either use `robin_hood::unordered_flat_map` or `robin_hood::unordered_node_map` directly. If you use `robin_hood::unordered_map` It tries to choose the layout that seems appropriate for your data.
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- **Custom allocator**. Node based representation has a custom bulk allocator that tries to make few memory allocations. All allocated memory is reused, so there won't be any allocation spikes. It's very fast as well.
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- **Optimized hash**. `robin_hood::hash` has custom implementations for integer types and for `std::string` that are very fast and falls back to `std::hash` for everything else.
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- **Depends on good Hashing**. For a really bad hash the performance will not only degrade like in `std::unordered_map`, the map will simply fail with an `std::overflow_error`. In practice, when using the standard `robin_hood::hash`, I have never seen this happening.
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## License
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Licensed under the MIT License. See the [LICENSE](https://github.com/martinus/robin-hood-hashing/blob/master/LICENSE) file for details.
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by martinus
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