AI engineering glossary · RAG vector search
What is nprobe?
nprobe: In IVF indexes, the number of clusters searched for each query. Raising it examines more vectors, which improves the chance of finding true neighbours but slows the search, so it is tuned to balance recall against latency for the product.
nprobe: an example
Moving nprobe from 5 to 40 raised recall@10 from 80% to 96% but made queries about 6 times slower.
Related terms
More RAG vector search terms
- Parent-document retrieval
- pgvector
- Post-filtering
- Pre-filtering
- Product quantisation
- Proposition indexing
- Query decomposition
- Query expansion
Where you learn it
nprobe is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.