AI engineering glossary · RAG vector search
What is ANN (approximate nearest neighbour search)?
Approximate nearest neighbour search (also called ANN): Search that returns vectors that are very likely, but not guaranteed, to be the closest ones, using an index to skip most comparisons. It makes searching hundreds of millions of vectors feasible in milliseconds, at the cost of occasionally missing a true neighbour.
Approximate nearest neighbour search: an example
An ANN index returns 9 of the true top 10 neighbours in 3 ms, while brute force needs 900 ms.
Related terms
More RAG vector search terms
Where you learn it
Approximate nearest neighbour search is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.