{
  "id": "reciprocal-rank-fusion",
  "title": "Reciprocal rank fusion",
  "kind": "implement",
  "summary": "Merge several ranked lists of document ids into one ranking with reciprocal rank fusion, optional list weights and a fixed tie rule.",
  "difficulty": "easy",
  "tags": ["rank-fusion", "hybrid-retrieval", "ranking", "retrieval"],
  "lesson": "phases/19-capstone-projects/65-hybrid-retrieval-bm25-dense",
  "cheatsheet": "rag",
  "minutes": 12,
  "entry": ["rrf_scores", "fuse"],
  "collections": ["rag-building-blocks"],
  "time_limit_s": 10,
  "mutants": {
    "first_appearance_ties": "Sorts by score only, so equal scores keep the order of first appearance and not the lower doc id first.",
    "ignore_weights": "Adds 1 / (k + rank) for every list and ignores the list weights.",
    "no_length_check": "Does not raise ValueError when the number of weights differs from the number of lists.",
    "rank_from_zero": "Counts ranks from 0, so the first document of a list adds 1 / k and not 1 / (k + 1)."
  }
}