nx_rrf.nx

nx_rrf.nx -- Reciprocal Rank Fusion (bits-up, Q16.16). module: nishi-core.search.rrf depends: fx.nx, syscalls.nx capability: CORE_COMPUTE wired_status: FULLY_WIRED genealogy_id: cormack_clarke_buettcher_2009_rrf WHY: the leaderboard needs to combine multiple ranking signals -- the source- tier PRIOR and the BM25 content score (nx_bm25), later novelty (nx_simhash) and provenance -- without tuning weights or breaking determinism. RRF fuses rankings by rank position alone: score(item) = sum over rankers of 1/(k + rank). It is parameter-free (k=60), monotone, and integer-exact in Q16.16. Crucially it neutralizes SEO: an item must rank well in BOTH the tier and the content ranker to top the fused list, so thin junk cannot ride domain authority and a unique low-tier page with strong content relevance still rises.