use double math internally when computing similarities (continue to r…

…eturn float at the end)

lucene/core/src/java/org/apache/lucene/util/VectorUtilDefaultProvider.java

@@ -26,7 +26,7 @@ final class VectorUtilDefaultProvider implements VectorUtilProvider {
 
   @Override
   public float dotProduct(float[] a, float[] b) {
-    float res = 0f;
+    double res = 0.0;
     /*
      * If length of vector is larger than 8, we use unrolled dot product to accelerate the
      * calculation.
@@ -36,7 +36,7 @@ public float dotProduct(float[] a, float[] b) {
       res += b[i] * a[i];
     }
     if (a.length < 8) {
-      return res;
+      return (float) res;
     }
     for (; i + 31 < a.length; i += 32) {
       res +=
@@ -87,43 +87,45 @@ public float dotProduct(float[] a, float[] b) {
               + b[i + 6] * a[i + 6]
               + b[i + 7] * a[i + 7];
     }
-    checkFinite(res, a, b, "dot product");
-    return res;
+    float resF = (float) res;
+    checkFinite(resF, a, b, "dot product");
+    return resF;
   }
 
   @Override
   public float cosine(float[] a, float[] b) {
-    float sum = 0.0f;
-    float norm1 = 0.0f;
-    float norm2 = 0.0f;
+    double sum = 0.0;
+    double norm1 = 0.0;
+    double norm2 = 0.0;
     int dim = a.length;
 
     for (int i = 0; i < dim; i++) {
-      float elem1 = a[i];
-      float elem2 = b[i];
+      double elem1 = a[i];
+      double elem2 = b[i];
       sum += elem1 * elem2;
       norm1 += elem1 * elem1;
       norm2 += elem2 * elem2;
     }
-    var r = (float) (sum / Math.sqrt(norm1 * norm2));
+    float r = (float) (sum / Math.sqrt(norm1 * norm2));
     checkFinite(r, a, b, "cosine");
     return r;
   }
 
   @Override
   public float squareDistance(float[] a, float[] b) {
-    float squareSum = 0.0f;
+    double squareSum = 0.0;
     int dim = a.length;
     int i;
     for (i = 0; i + 8 <= dim; i += 8) {
       squareSum += squareDistanceUnrolled(a, b, i);
     }
     for (; i < dim; i++) {
-      float diff = a[i] - b[i];
+      double diff = a[i] - b[i];
       squareSum += diff * diff;
     }
-    checkFinite(squareSum, a, b, "square distance");
-    return squareSum;
+    float r = (float) squareSum;
+    checkFinite(r, a, b, "square distance");
+    return r;
   }
 
   private static void checkFinite(float r, float[] a, float[] b, String optype) {
@@ -148,15 +150,15 @@ private static void checkFinite(float r, float[] a, float[] b, String optype) {
     }
   }
 
-  private static float squareDistanceUnrolled(float[] v1, float[] v2, int index) {
-    float diff0 = v1[index + 0] - v2[index + 0];
-    float diff1 = v1[index + 1] - v2[index + 1];
-    float diff2 = v1[index + 2] - v2[index + 2];
-    float diff3 = v1[index + 3] - v2[index + 3];
-    float diff4 = v1[index + 4] - v2[index + 4];
-    float diff5 = v1[index + 5] - v2[index + 5];
-    float diff6 = v1[index + 6] - v2[index + 6];
-    float diff7 = v1[index + 7] - v2[index + 7];
+  private static double squareDistanceUnrolled(float[] v1, float[] v2, int index) {
+    double diff0 = v1[index + 0] - v2[index + 0];
+    double diff1 = v1[index + 1] - v2[index + 1];
+    double diff2 = v1[index + 2] - v2[index + 2];
+    double diff3 = v1[index + 3] - v2[index + 3];
+    double diff4 = v1[index + 4] - v2[index + 4];
+    double diff5 = v1[index + 5] - v2[index + 5];
+    double diff6 = v1[index + 6] - v2[index + 6];
+    double diff7 = v1[index + 7] - v2[index + 7];
     return diff0 * diff0
         + diff1 * diff1
         + diff2 * diff2