Link & code is an indexing method that combines HNSW indexing with compression and exploits the neighborhood structure of the similarity graph to improve the reconstruction. It is described in
@inproceedings{link_and_code,
author = {Matthijs Douze and Alexandre Sablayrolles and Herv\'e J\'egou},
title = {Link and code: Fast indexing with graphs and compact regression codes},
booktitle = {CVPR},
year = {2018}
}
ArXiV here
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