[GitHub] [lucene] agorlenko commented on a diff in pull request #11946: add similarity threshold for hnsw

[GitBox <gi...@apache.org>]

agorlenko commented on code in PR #11946:
URL: https://github.com/apache/lucene/pull/11946#discussion_r1025027735


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lucene/core/src/test/org/apache/lucene/index/TestExitableDirectoryReader.java:
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@@ -494,13 +498,12 @@ public void testVectorValues() throws IOException {
           ExitingReaderException.class,
           () ->
               leaf.searchNearestVectors(
-                  "vector", new float[dimension], 5, leaf.getLiveDocs(), Integer.MAX_VALUE));
+                  "vector", target, 5, leaf.getLiveDocs(), Integer.MAX_VALUE));

Review Comment:
   There is a problem, because cosine similarity is not specified for zero vectors. As a result we have NaN score. I thought that it would be better not to handle that special case and get rid of docs with score equals NaN. We had the same behavior earlier, except the case with start point: https://github.com/apache/lucene/blob/a18b62ded49f1b091de7029716d6f63c06a36fc0/lucene/core/src/java/org/apache/lucene/util/hnsw/HnswGraphSearcher.java#L223-L225 We check acceptOrds.get here and raise an exception.  But actually we don't need to check acceptOrds in the case of zero vector and the cosine similarity. So I think it would be better just not to consider that case if we want to test ExitingReaderException and just define the target as a random float vector.



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