Summary:
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/2255
The `DistanceComputer` object is derived from an Index (obtained with `get_distance_computer()`). It maintains a current query and quickly computes distances from that query to any item in the database. This is useful, eg. for the IndexHNSW and IndexNSG that rely on query-to-point comparisons in the datasets.
This diff introduces the `FlatCodesDistanceComputer`, that inherits from `DistanceComputer` for Flat indexes. In addition to the distance-to-item function, it adds a `distance_to_code` that computes the distance from any code to the current query, even if it is not stored in the index.
This is implemented for all FlatCode indexes (IndexFlat, IndexPQ, IndexScalarQuantizer and IndexAdditiveQuantizer).
In the process, the two classes were extracted to their own header file `impl/DistanceComputer.h`
Reviewed By: beauby
Differential Revision: D34863609
fbshipit-source-id: 39d8c66475e55c3223c4a6a210827aa48bca292d
* Pass compilation in current state
* Fix formatting and add missing parts
* Define DistanceComputer
* Add documentation to name changed on DistanceComputer::operator()()
* Apply suggestions from code review
Changes in docs
Co-Authored-By: Eduardo Pinho <enet4mikeenet@gmail.com>
* Updated MetricType
Matthijs Douze
Lucas Hosseini
Prabhat Roy
Jose Truyol