1 files changed, 34 insertions, 0 deletions
diff --git a/container-search/src/main/java/com/yahoo/search/ranking/ReciprocalRankNormalizer.java b/container-search/src/main/java/com/yahoo/search/ranking/ReciprocalRankNormalizer.java
new file mode 100644
index 00000000000..fca920a7a65
--- /dev/null
+++ b/container-search/src/main/java/com/yahoo/search/ranking/ReciprocalRankNormalizer.java
@@ -0,0 +1,34 @@
+// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.search.ranking;
+
+import java.util.Arrays;
+
+class ReciprocalRankNormalizer extends Normalizer {
+
+    private final double k;
+
+    ReciprocalRankNormalizer(int maxSize, double k) {
+        super(maxSize);
+        this.k = k;
+    }
+
+    static record IdxScore(int index, double score) {}
+
+    void normalize() {
+        if (size < 1) return;
+        IdxScore[] temp = new IdxScore[size];
+        for (int i = 0; i < size; i++) {
+            double val = data[i];
+            if (Double.isNaN(val)) val = Double.NEGATIVE_INFINITY;
+            temp[i] = new IdxScore(i, val);
+        }
+        Arrays.sort(temp, (a, b) -> Double.compare(b.score, a.score));
+        for (int i = 0; i < size; i++) {
+            int idx = temp[i].index;
+            double old = data[idx];
+            data[idx] = 1.0 / (k + 1.0 + i);
+        }
+    }
+
+    String normalizing() { return "reciprocal-rank{k:" + k + "}"; }
+}