IVF_PQ_FS is the optimized version of IVF_PQ that uses SIMD to speed up search in a low-dimensional space. Currently the constraint of nbits parameter is 4.

Building parameters:

nlistNumber of cluster units[1,65536]
mNumber of factors of product quantizationNeeds to be divisible by vector dimension
Table 15 Building Parameter of IVF_PQ_FS

Search parameters:

nprobeNumber of units to query[1, nlist]
Table 16 Search Parameter of IVF_PQ_FS