Recall@k
Of the documents that should answer a query, the fraction that appear in the top k retrieved.
By Lattice editorial · Entry last reviewed · method
What it implies
The single diagnostic that separates a retrieval problem from a generation problem: if the answer is not in the top k, no prompt change will help. Check it on twenty real queries before changing anything. It costs an hour and determines everything that follows.
Related terms
- RerankingRe-scoring retrieved candidates with a slower, more accurate model before the generator sees them.
- Vector indexAn approximate structure — usually HNSW or an IVF variant — that finds nearest neighbours without scanning every vector.
- Hybrid searchCombining lexical retrieval (BM25) with vector retrieval, so exact matches and semantic matches are both found.