The license was changed from BSD+Patents to MIT.
Changelog:
- propagates exceptions raised in sub-indexes of IndexShards and IndexReplicas;
- support for searching several inverted lists in parallel (parallel_mode != 0);
- better support for PQ codes where nbit != 8 or 16;
- IVFSpectralHash implementation: spectral hash codes inside an IVF;
- 6-bit per component scalar quantizer (4 and 8 bit were already supported);
- combinations of inverted lists: HStackInvertedLists and VStackInvertedLists;
- configurable number of threads for OnDiskInvertedLists prefetching (including 0=no prefetch);
- more test and demo code compatible with Python 3 (print with parentheses);
- refactored benchmark code: data loading is now in a single file.