Faster Population Counts Using AVX2 Instructions
Data Structures and Algorithms
2018-09-07 v9
Abstract
Counting the number of ones in a binary stream is a common operation in database, information-retrieval, cryptographic and machine-learning applications. Most processors have dedicated instructions to count the number of ones in a word (e.g., popcnt on x64 processors). Maybe surprisingly, we show that a vectorized approach using SIMD instructions can be twice as fast as using the dedicated instructions on recent Intel processors. The benefits can be even greater for applications such as similarity measures (e.g., the Jaccard index) that require additional Boolean operations. Our approach has been adopted by LLVM: it is used by its popular C compiler (clang).
Cite
@article{arxiv.1611.07612,
title = {Faster Population Counts Using AVX2 Instructions},
author = {Wojciech Muła and Nathan Kurz and Daniel Lemire},
journal= {arXiv preprint arXiv:1611.07612},
year = {2018}
}
Comments
Software is at https://github.com/CountOnes/hamming_weight