add Normalizer classes

3 files changed, 94 insertions, 0 deletions

diff --git a/container-search/src/main/java/com/yahoo/search/ranking/LinearNormalizer.java b/container-search/src/main/java/com/yahoo/search/ranking/LinearNormalizer.java
new file mode 100644
index 00000000000..0f87d0f0b52
--- /dev/null
+++ b/container-search/src/main/java/com/yahoo/search/ranking/LinearNormalizer.java
@@ -0,0 +1,31 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.search.ranking;
+
+class LinearNormalizer extends Normalizer {
+
+    LinearNormalizer(String name, String input, int maxSize) {
+        super(name, input, maxSize);
+    }
+
+    void normalize() {
+        double min = data[0];
+        double max = data[0];
+        for (int i = 1; i < size; i++) {
+            min = Math.min(min, data[i]);
+            max = Math.max(max, data[i]);
+        }
+        min = Math.max(min, -Float.MAX_VALUE);
+        max = Math.min(max, Float.MAX_VALUE);
+        double scale = 0.0;
+        double midpoint = (min + max) * 0.5;
+        if (max > min) {
+            scale = 1.0 / (max - min);
+        }
+        for (int i = 0; i < size; i++) {
+            double old = data[i];
+            data[i] = 0.5 + scale * (old - midpoint);
+        }
+    }
+
+    String normalizing() { return "linear"; }
+}
diff --git a/container-search/src/main/java/com/yahoo/search/ranking/Normalizer.java b/container-search/src/main/java/com/yahoo/search/ranking/Normalizer.java
new file mode 100644
index 00000000000..987065b29f2
--- /dev/null
+++ b/container-search/src/main/java/com/yahoo/search/ranking/Normalizer.java
@@ -0,0 +1,31 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.search.ranking;
+
+abstract class Normalizer {
+
+    private final String name;
+    private final String needInput;
+    protected final double[] data;
+    protected int size = 0;
+
+    Normalizer(String name, String needInput, int maxSize) {
+        this.name = name;
+        this.needInput = needInput;
+        this.data = new double[maxSize];
+    }
+
+    int addInput(double value) {
+        data[size] = value;
+        return size++;
+    }
+
+    double getOutput(int index) { return data[index]; }
+
+    String name() { return name; }
+
+    String input() { return needInput; }
+
+    abstract void normalize();
+
+    abstract String normalizing();
+}
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..7862e54c32e
--- /dev/null
+++ b/container-search/src/main/java/com/yahoo/search/ranking/ReciprocalRankNormalizer.java
@@ -0,0 +1,32 @@
+// Copyright Yahoo. 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(String name, String input, int maxSize, double k) {
+        super(name, input, 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++) {
+            temp[i] = new IdxScore(i, data[i]);
+        }
+        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 + "}"; }
+}