[ninja3925]

Interestingly, FAISS does exactly that before doing Product Quantization and it works very well (errors are much lower compared to no rotation). They call it “optimal PQ”. During training time, they iterate to find a good candidate and save the best one.

Perhaps not entirely coincidentally, FAISS is also maintained by FB.

https://faiss.ai/cpp_api/struct/structfaiss_1_1OPQMatrix.htm...