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AI & Machine Learning · Intermediate

Approximate Nearest Neighbor (ANN)

Similarity search that returns near-closest vectors quickly by accepting a small loss in accuracy.

Definition

Exact k-NN over millions of vectors is slow, so ANN algorithms such as HNSW, IVF and ScaNN trade a little recall for orders-of-magnitude speedups. Recall@k measures how often true neighbors are returned.

Exam tip

ANN trades exactness for speed; tune index parameters to balance recall and latency.

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