Julie Tibshirani created LUCENE-10404:
-----------------------------------------
Summary: Use hash set for visited nodes in HNSW search?
Key: LUCENE-10404
URL: https://issues.apache.org/jira/browse/LUCENE-10404
Project: Lucene - Core
Issue Type: Improvement
Reporter: Julie Tibshirani
While searching each layer, HNSW tracks the nodes it has already visited using
a BitSet. We could look into using something like IntHashSet instead. I tried
out the idea quickly by switching to IntIntHashMap (which has already been
copied from hppc) and saw an improvement in index performance.
**Baseline:** 760896 msec to write vectors
**Using IntIntHashMap:** 733017 msec to write vectors
I noticed search performance actually got a little bit worse with the change --
that is something to look into.
For background, it's good to be aware that HNSW can visit a lot of nodes. For
example, on the glove-100-angular dataset with ~1.2 million docs, HNSW search
visits ~1000 - 15,000 docs depending on the recall. This number can increase
when searching with deleted docs, especially if you hit a "pathological" case
where the deleted docs happen to be closest to the query vector.
--
This message was sent by Atlassian Jira
(v8.20.1#820001)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org
For additional commands, e-mail: issues-h...@lucene.apache.org
