[lucene] branch main updated: LUCENE-10146: Add note that dot product is preferred over cosine (#400)

[ju...@apache.org]

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julietibs pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/lucene.git


The following commit(s) were added to refs/heads/main by this push:
     new 6bb2bbc  LUCENE-10146: Add note that dot product is preferred over cosine (#400)
6bb2bbc is described below

commit 6bb2bbcd6ab2e07a646c17351437ea5210b08004
Author: Julie Tibshirani <ju...@elastic.co>
AuthorDate: Wed Oct 20 09:50:25 2021 -0700

    LUCENE-10146: Add note that dot product is preferred over cosine (#400)
    
    While VectorSimilarityFunction#COSINE is helpful when you need to preserve the
    original vectors, it is significantly slower than DOT_PRODUCT. This commit adds
    javadocs to COSINE explaining that dot product is the fastest option.
---
 .../src/java/org/apache/lucene/index/VectorSimilarityFunction.java | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lucene/core/src/java/org/apache/lucene/index/VectorSimilarityFunction.java b/lucene/core/src/java/org/apache/lucene/index/VectorSimilarityFunction.java
index a133bf2..a237e3d 100644
--- a/lucene/core/src/java/org/apache/lucene/index/VectorSimilarityFunction.java
+++ b/lucene/core/src/java/org/apache/lucene/index/VectorSimilarityFunction.java
@@ -56,7 +56,12 @@ public enum VectorSimilarityFunction {
     }
   },
 
-  /** Cosine similarity */
+  /**
+   * Cosine similarity. NOTE: the preferred way to perform cosine similarity is to normalize all
+   * vectors to unit length, and instead use {@link VectorSimilarityFunction#DOT_PRODUCT}. You
+   * should only use this function if you need to preserve the original vectors and cannot normalize
+   * them in advance.
+   */
   COSINE {
     @Override
     public float compare(float[] v1, float[] v2) {