the choice of faiss index

[jcyk]

hi, thanks for open-sourcing the project. great work!

I have questions on the choice of faiss index, i'd really appreciate if you find time to clarify:

0. Could you please share the detailed procedure of how you index wikipedia?

1. Is IVF1048576_HNSW32_SQ8 and search with nprobe=64a precise summary of your choice?

2. I find in open/build_index.py, there is a function named merge_indexes. Did you build multiple sub-indexes then merge? or did not? because I feel the choice may have some effect on the performance.

3. just more specific Q1, the process of building index seems quite complicated in your code as follows. by default, it goes through
   https://github.com/uwnlp/denspi/blob/f540b6a547f012823fc6c2bb10077df6bccc13a6/open/run_index.py#L121
   https://github.com/uwnlp/denspi/blob/f540b6a547f012823fc6c2bb10077df6bccc13a6/open/run_index.py#L126-L131
   https://github.com/uwnlp/denspi/blob/f540b6a547f012823fc6c2bb10077df6bccc13a6/open/run_index.py#L134-L137
   then
   https://github.com/uwnlp/denspi/blob/f540b6a547f012823fc6c2bb10077df6bccc13a6/open/run_index.py#L148
   https://github.com/uwnlp/denspi/blob/f540b6a547f012823fc6c2bb10077df6bccc13a6/open/run_index.py#L164

Can the following two lines encode the same idea?

index = faiss.index_factory(d, "IVF1048576_HNSW32,SQ8")
index.train(data)

thanks!