Inverted File Index (IVF) is a space-partitioning (Voronoi Partitioning) coarse-clustering ANN retrieval framework; during indexing, K-Means partitions the vector space into
Nlist Voronoi cells, each managing an Inverted List of vectors within that centroid; during query, it identifies the
Nprobe nearest centroids and restricts search strictly to these lists; in residual variants (IVF-PQ/IVF-SQ), the residual vector
r=x−c relative to its centroid is quantized.