Support for 16 bit quantization

[patelprateek]

Are there any plans for supporting 16 bit floats (fp16 and Bfloat16) quantization for embeddings. I would assume it would be an easier choice that doesn't separately need to train any codebooks and gives some headroom for scaling indexes without compromising on recall quality

[numb3r3]

That's a good idea. Actually, we are investigating whether bf16 would benefits (and how much) the HNSW search.

[patelprateek]

AFAIk FP16C allows to convert between fp16 and fp32 should be available on most AVX CPUs. AVX512-fp16 provides the ability to perform maths on fp16 directly, but is only supported by a very small number of the latest CPUs.
For BF16 I am not aware if any architecture supports vectorized math yet . So i would assume we would have to convert back and forth , might be increased search latency (if not bottlenecked on memory bandwidth) but saves quite a bit on embedding space with little degradation on recall if any