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https://issues.apache.org/jira/browse/LUCENE-9918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17391245#comment-17391245
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Gautam Worah edited comment on LUCENE-9918 at 8/1/21, 10:12 PM:
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Hey [~gsmiller] , I noticed that in the micro benchmark code in your
lucene-pfor-benchmark [repo |#L15],] the main loop runs 10 times I think?
Some
[sources|http://daniel-strecker.com/blog/2020-01-14_auto_vectorization_in_java/#Output%20Interpretation]
suggest that usually the JIT compiler compiles and optimizes statements as and
when it sees that a particular operation is repeated multiple times. So it
first optimizes them a little and them some more iff it sees them again. So
maybe we just need to repeat the experiment with say 100k iterations?
was (Author: gworah):
Hey @gmiller, I noticed that in the micro benchmark code in your
lucene-pfor-benchmark [repo
|[https://github.com/gsmiller/lucene-pfor-benchmark/blob/main/src/main/java/gsmiller/DecodeBenchmark.java#L15],]
the main loop runs 10 times I think?
Some
[sources|http://daniel-strecker.com/blog/2020-01-14_auto_vectorization_in_java/#Output%20Interpretation]
suggest that usually the JIT compiler compiles and optimizes statements as and
when it sees that a particular operation is repeated multiple times. So it
first optimizes them a little and them some more iff it sees them again. So
maybe we just need to repeat the experiment with say 100k iterations?
> Can PForUtil be further auto-vectorized?
> ----------------------------------------
>
> Key: LUCENE-9918
> URL: https://issues.apache.org/jira/browse/LUCENE-9918
> Project: Lucene - Core
> Issue Type: Task
> Components: core/codecs
> Affects Versions: main (9.0)
> Reporter: Greg Miller
> Priority: Minor
>
> While working on LUCENE-9850, we discovered the loop in PForUtil::prefixSumOf
> is not getting auto-vectorized by the HotSpot compiler. We tried a few
> different tweaks to see if we could change this, but came up empty. There are
> some additional suggestions in the related
> [PR|https://github.com/apache/lucene/pull/69#discussion_r608412309] that
> could still be experimented with, and it may be worth doing so to see if
> further improvements could be squeezed out.
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