Add a HNSW collector that exits early when nearest neighbor queue saturates #14094
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lucene/core/src/java/org/apache/lucene/search/HnswQueueSaturationCollector.java
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lucene/core/src/java/org/apache/lucene/search/HnswQueueSaturationCollector.java
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lucene/core/src/java/org/apache/lucene/search/HnswQueueSaturationCollector.java
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lucene/core/src/test/org/apache/lucene/search/HnswQueueSaturationCollectorTest.java
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| public interface HnswKnnCollector extends KnnCollector { | ||
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| /** Indicates exploration of the next HNSW candidate graph node. */ | ||
| void nextCandidate(); | ||
| } |
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I think this kind of collector is OK. But it makes most sense to me to be a delegate collector. An abstract collector to KnnCollector.Delegate.
Then, I also think that the OrdinalTranslatingKnnCollector should inherit directly from HnswKnnCollector always assuming that the passed in collector is a HnswKnnCollector.
Note, the default behavior for HnswKnnCollector#nextCandidate can simply be nothing, allowing for overriding.
This might require a new HnswGraphSearcher#search interface to keep the old collector actions, but it can be simple to add a new one that accepts a HnswKnnCollector and delegate to it with new HnswKnnCollector(KnnCollector delegate).
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I adjusted my refactoring for the seeded queries similarly. It seems nicer IMO: #14170
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thanks Ben. I'll incorporate your suggestions once #14170 is in.
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made HnswKnnCollector a KnnCollector.Decorator in c6dbf7e
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updated results (Cohere-768, 200k docs, merge disabled) baseline candidate |
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reference paper |
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I've updated this and moved the early termination logic not to kick in by default but to be based on a (wrapping) |
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updated maxconn=32baseline candidate@default candidate@sat=0.995,patience=maxconn(32) candidate@sat=0.95,patience=fanout(50) candidate@sat=0.995,patience=fanout(50) maxconn=64baseline candidate@default candidate@sat=0.995,patience=maxconn(64) candidate@sat=0.95,patience=fanout(50) candidate@sat=0.995,patience=fanout(50) |
| super(collector); | ||
| } | ||
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| /** Indicates exploration of the next HNSW candidate graph node. */ |
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nit: suggest "triggers" instead of "indicates"
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| @Override | ||
| public String toString(String field) { | ||
| return null; |
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Perhaps add some name here, maybe in the future it will be easier to debug?
This introduces a
HnswKnnCollectorinterface, extendingKnnCollectorfor HNSW, to make it possible to hook into HNSW execution for optimizations.It then adds a new collector which uses a saturation-based threshold to dynamically halt HNSW graph exploration, in order to early exit when the exploration of new candidates is unlikely to lead to addition of new neighbors.
The new collector records the number of added neighbors upon exploration of a new candidate (a HNSW node) and it compares it with the number of neighbors added while exploring the previous candidate, when the rate of added neighbors plateaus for a number of consecutive iterations, it stops graph exploration (
earlyTerminatereturnstrue).