HashEnsemble
HashEnsemble is just an ensemble of a few good hash functions (e.g. xxhash).
Dependencies
Install:
chmod +x ./scripts/before_install.<OS>.sh
cd ./scripts && ./install_dependencies.<OS>.shwhere <OS> can be linux (for Ubuntu) or osx (for MacOs)
!!ONLY REQUIRED if you want to use benchmarks!!
Build
mkdir build && cd build
cmake ..
makeBenchmarks
On a workstation with Intel(R) Core(TM) i7-9800X CPU @ 3.80GHz running Ubuntu 18.04, we obtained the following results
| name | key type | speed (million keys per second) | raw_speed (million keys per second) | degradation (%) | collision_1 (%) | collision_2 (%) | collision_5 (%) | collision_10 (%) |
|---|---|---|---|---|---|---|---|---|
| xxhash | 64-bit integer | 601.86 | 1065.02 | 43.49 | 36.79 | 10.66 | 1.87 | 0.48 |
| wyhash | 64-bit integer | 944.51 | 1518.76 | 37.81 | 36.78 | 10.65 | 1.87 | 0.48 |
| MurmurHash3 | 64-bit integer | 201.88 | 147.03 | -37.30 | 36.79 | 10.66 | 1.88 | 0.49 |
| Spooky | 64-bit integer | 147.88 | 163.45 | 9.53 | 36.78 | 10.65 | 1.87 | 0.48 |
| xxhash_ct | 64-bit integer | 1075.82 | 1063.99 | -1.11 | 36.79 | 10.66 | 1.87 | 0.48 |
| wyhash_ct | 64-bit integer | 1026.66 | 1590.61 | 35.46 | 36.78 | 10.65 | 1.87 | 0.48 |
_rt means the hash function was selected during the runtime whereas _ct means selection was done during compile time. collision_x is the collision ratio when using the numnber of bins as x times as that of keys.
Overall Performance:
wyhash > xxhash > MurmurHash3 > Spooky
Significant performance degradation was obversed for wyhash (**Reasons to be figured out). So if you
decide to use wyhash and speed matters much in your program, then you are not suggested to use HashEnsemble.
For more professional benchmarks on more hash functions, please refer to aappleby/smhasher and rurban/smhasher.
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