Summary:
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/2132
This diff adds the class IndexFlatCodes that becomes the parent of all "flat" encodings.
IndexPQ
IndexFlat
IndexAdditiveQuantizer
IndexScalarQuantizer
IndexLSH
Index2Layer
The other changes are:
- for IndexFlat, there is no vector<float> with the data anymore. It is replaced with a `get_xb()` function. This broke quite a few external codes, that this diff also attempts to fix.
- I/O functions needed to be adapted. This is done without changing the I/O format for any index.
- added a small contrib function to get the data from the IndexFlat
- the functionality has been made uniform, for example remove_ids and add are now in the parent class.
Eventually, we may support generic storage for flat indexes, similar to `InvertedLists`, eg to memmap the data, but this will again require a big change.
Reviewed By: wickedfoo
Differential Revision: D32646769
fbshipit-source-id: 04a1659173fd51b130ae45d345176b72183cae40
c0052c1533