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#15024: Improve prefix sum in Lucene99HnswVectorsReader #15790

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Merged
kaivalnp merged 3 commits into from
Mar 9, 2026
Merged

#15024: Improve prefix sum in Lucene99HnswVectorsReader #15790

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0b322e4
Improve prefix sum in Lucene99HnswVectorsReader
leng25 Feb 28, 2026
94352d6
Merge branch 'apache:main' into improve-hnsw-prefix-sum
leng25 Feb 28, 2026
b63e8b9
Move CHANGES.txt entry from 11.0.0 to 10.5.0
leng25 Mar 9, 2026
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2 changes: 2 additions & 0 deletions lucene/CHANGES.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -239,6 +239,8 @@ Optimizations

* GITHUB#15742: Optimize int4 dotProduct and squareDistance computations by replacing vector conversions with reinterpret casting + bit manipulation. (Trevor McCulloch, Kaival Parikh)

* GITHUB#15024: Improve prefix sum computation in Lucene99HnswVectorsReader for faster neighbor decoding. (Luis Negrin)

Bug Fixes
---------------------
* GITHUB#15668: Fix UnsupportedOperationException in WeightedSpanTermExtractor by
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12 changes: 7 additions & 5 deletions lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsReader.java
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Expand Up @@ -561,15 +561,17 @@ public void seek(int level, int targetOrd) throws IOException {
arcCount = dataIn.readVInt();
assert arcCount <= currentNeighborsBuffer.length : "too many neighbors: " + arcCount;
if (arcCount > 0) {
int sum = 0;
if (version >= VERSION_GROUPVARINT) {
GroupVIntUtil.readGroupVInts(dataIn, currentNeighborsBuffer, arcCount);
for (int i = 1; i < arcCount; i++) {
currentNeighborsBuffer[i] = currentNeighborsBuffer[i - 1] + currentNeighborsBuffer[i];
for (int i = 0; i < arcCount; i++) {
sum += currentNeighborsBuffer[i];
currentNeighborsBuffer[i] = sum;
}
} else {
currentNeighborsBuffer[0] = dataIn.readVInt();
for (int i = 1; i < arcCount; i++) {
currentNeighborsBuffer[i] = currentNeighborsBuffer[i - 1] + dataIn.readVInt();
for (int i = 0; i < arcCount; i++) {
sum += dataIn.readVInt();
currentNeighborsBuffer[i] = sum;
}
}
}
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