buildKnnRankMap(Knn knn) {
return wrapper;
}
+ /**
+ * Expands RRF into arithmetic rank expressions that the server understands.
+ * The server has no native {@code $rrf} operator — RRF is a client-side formula:
+ * {@code -(sum(weight_i / (k + rank_i)))}
+ *
+ * When {@code normalize} is enabled, each weight is first divided by the sum of all
+ * weights before expansion (i.e., {@code w_i' = w_i / sum(w)}).
+ *
+ * Each term becomes: {@code $div { left: $val(weight), right: $sum[$val(k), $knn(...)] }}
+ * All terms are summed (single term: {@code $div} directly, no {@code $sum} wrapper),
+ * then negated (RRF: higher is better → Chroma: lower is better).
+ */
static Map buildRrfRankMap(Rrf rrf) {
- Map rrfMap = new LinkedHashMap();
- List> ranksList = new ArrayList>();
- for (Rrf.RankWithWeight rw : rrf.getRanks()) {
- Map entry = new LinkedHashMap();
- entry.put("rank", buildKnnRankMap(rw.getKnn()));
- entry.put("weight", rw.getWeight());
- ranksList.add(entry);
- }
- rrfMap.put("ranks", ranksList);
- rrfMap.put("k", rrf.getK());
- if (rrf.isNormalize()) rrfMap.put("normalize", true);
- Map wrapper = new LinkedHashMap();
- wrapper.put(WIRE_RRF, rrfMap);
- return wrapper;
+ List ranks = rrf.getRanks();
+ double[] weights = new double[ranks.size()];
+ for (int i = 0; i < ranks.size(); i++) {
+ weights[i] = ranks.get(i).getWeight();
+ }
+ // Normalize weights if requested (divide each by the sum of all weights).
+ // Rrf.build() guarantees weightSum >= 1e-9, so sum should always be positive here.
+ if (rrf.isNormalize()) {
+ double sum = 0;
+ for (double w : weights) sum += w;
+ if (sum <= 1e-9) {
+ throw new IllegalStateException(
+ "RRF weight sum is effectively zero (" + sum + "); this should have been rejected by Rrf.build()");
+ }
+ for (int i = 0; i < weights.length; i++) weights[i] /= sum;
+ }
+ // Build terms: weight_i / (k + rank_i)
+ List> terms = new ArrayList>();
+ for (int i = 0; i < ranks.size(); i++) {
+ Map valWeight = new LinkedHashMap();
+ valWeight.put("$val", weights[i]);
+
+ Map valK = new LinkedHashMap();
+ valK.put("$val", (double) rrf.getK());
+
+ Map knnMap = buildKnnRankMap(ranks.get(i).getKnn());
+
+ // denominator = $sum[$val(k), $knn]
+ List