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https://issues.apache.org/jira/browse/IMPALA-8726?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Becker updated IMPALA-8726:
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Attachment: no_vector.png
> Autovectorisation leads to worse performance in bit unpacking
> -------------------------------------------------------------
>
> Key: IMPALA-8726
> URL: https://issues.apache.org/jira/browse/IMPALA-8726
> Project: IMPALA
> Issue Type: Improvement
> Reporter: Daniel Becker
> Priority: Minor
>
> The compiler (GCC 4.9.2) autovectorises bit unpacking for bit widths 1, 2, 4
> and 8 (function BitPacking::UnpackValues), but this leads to actually worse
> performance (see the attached graph). We should consider whether it is worth
> disabling autovectorisation for bit unpacking, but future compiler versions
> may do a better job.
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