Summary:
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/2682
IndexShards normally sees the indexes as opaque, so there is no way to factrorize the coarse quantizer.
This diff introduces IndexIVFShards that handles IVF indexes with a common quantizer so that the quantization is computed only once.
Reviewed By: alexanderguzhva
Differential Revision: D42781513
fbshipit-source-id: 441316eff4c1ba0468501c456af9194ea5f042d6