benwtrent opened a new pull request, #12789: URL: https://github.com/apache/lucene/pull/12789
While doing some performance testing and digging into flamegraphs, I noticed for smaller vectors (96dim float32), we were losing a fair bit of time within the `SparseFixedBitSet#getAndSet` method. I am assuming we are using `SparseFixedBitSet` for performance reasons to reduce memory usage? I ran some tests with topK=100 and fanOut=1000. To check memory usage, in a separate run, I printed out `bitSet.ramBytesUsed()` after every search. I tested using FixedBitSet instead with GLOVE and saw almost a 10% improvement in search speed: ``` completed 1000 searches in 803 ms: 1245 QPS CPU time=801ms checking results 0.695 0.80 100000 1000 16 100 1100 0 1.00 post-filter ``` Vs. baseline ``` completed 1000 searches in 873 ms: 1145 QPS CPU time=873ms checking results 0.695 0.87 100000 1000 16 100 1100 0 1.00 post-filter ``` The total ramBytesUsed (allocated and then gc'd collected) for 1000 searches over glove was `21288656` bytes. For fixed bit set, every search only allocates `12544`, which pans out to `12544000` bytes (actually less than sparse). To confirm this was still true for larger vectors and a larger graph, I tested against 400k cohere vectors (same params). There is a bit more noise in the measurements, so I averaged the latency over 4 runs: candidate: `6.115` with a min: `5.96` baseline: `6.23` with a min: `6.15`. Total memory usage for sparse: `103982464` vs for total memory usage for Fixed `50040000` Do we know the goal for using a SparseFixedBitSet and under what conditions it would actually perform better than a regular FixedBitSet? I will happily test some more. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
