[GitHub] [lucene] msokolov commented on pull request #12311: Integrate the Incubating Panama Vector API

["msokolov (via GitHub)" <gi...@apache.org>]

msokolov commented on PR #12311:
URL: https://github.com/apache/lucene/pull/12311#issuecomment-1557119416

   When I had tried this before I did something like:
   
   ```
   +    ShortVector acc = ShortVector.zero(SHORT_SPECIES);
   +    int l = 0;
   +    for (; l < BYTE_SPECIES.loopBound(len); l += BYTE_SPECIES.length()) {
   +      ByteVector va = ByteVector.fromArray(BYTE_SPECIES, a.bytes, aOffset + l);
   +      ByteVector vb = ByteVector.fromArray(BYTE_SPECIES, b.bytes, bOffset + l);
   +
   +      Vector<Short> vas = va.castShape(SHORT_SPECIES, 0);
   +      Vector<Short> vbs = vb.castShape(SHORT_SPECIES, 0);
   +      acc = acc.add(vas.mul(vbs));
   +
   +      vas = va.castShape(SHORT_SPECIES, 1);
   +      vbs = vb.castShape(SHORT_SPECIES, 1);
   +      acc = acc.add(vas.mul(vbs));
   +    }
   +    long total = acc.reduceLanesToLong(VectorOperators.ADD);
   ```
   
   I don't have perf numbers any more - no idea whether this is better than what you have already - probably not, but it might be worth trying castShape?


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