kaivalnp commented on code in PR #15736:
URL: https://github.com/apache/lucene/pull/15736#discussion_r2835049070
##########
lucene/core/src/java25/org/apache/lucene/internal/vectorization/PanamaVectorUtilSupport.java:
##########
@@ -610,11 +610,10 @@ private static int int4DotProductSinglePackedBody(
prod8a.convertShape(ZERO_EXTEND_B2S, Int4Constants.SHORT_SPECIES,
0);
acc1 = acc1.add(prod16a);
}
- Vector<Integer> intAcc0 = acc0.convert(S2I, 0);
- Vector<Integer> intAcc1 = acc0.convert(S2I, 1);
- Vector<Integer> intAcc2 = acc1.convert(S2I, 0);
- Vector<Integer> intAcc3 = acc1.convert(S2I, 1);
- sum +=
intAcc0.add(intAcc1).add(intAcc2).add(intAcc3).reinterpretAsInts().reduceLanes(ADD);
+ ShortVector accShort = acc0.add(acc1);
+ Vector<Integer> intAcc0 = accShort.convert(ZERO_EXTEND_S2I, 0);
+ Vector<Integer> intAcc1 = accShort.convert(ZERO_EXTEND_S2I, 1);
+ sum += intAcc0.add(intAcc1).reinterpretAsInts().reduceLanes(ADD);
}
Review Comment:
@mccullocht In fact, I went one step ahead and removed all `convert`
operations, specially shape changing ones -- so we load and operate on the same
number of bytes (see [this
commit](https://github.com/apache/lucene/commit/9059dc570afb9440b0178faaf8baa90879decbf0)),
and I get much better performance on my machine (\~25% bump from this PR):
```
Benchmark (size)
Mode Cnt Score Error Units
VectorUtilBenchmark.binaryHalfByteDotProductSinglePackedScalar 1024
thrpt 15 2.450 ± 0.006 ops/us
VectorUtilBenchmark.binaryHalfByteDotProductSinglePackedVector 1024
thrpt 15 19.166 ± 0.028 ops/us
```
Edit: I only made changes for `int4DotProductSinglePackedBody` + when the
preferred bit width is 256 -- you may need equivalent changes for other
functions + bit widths to reproduce
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