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https://issues.apache.org/jira/browse/ARROW-10058?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Antoine Pitrou reassigned ARROW-10058:
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Assignee: Antoine Pitrou
> [C++] Investigate performance of LevelsToBitmap without BMI2
> ------------------------------------------------------------
>
> Key: ARROW-10058
> URL: https://issues.apache.org/jira/browse/ARROW-10058
> Project: Apache Arrow
> Issue Type: Sub-task
> Components: C++
> Reporter: Antoine Pitrou
> Assignee: Antoine Pitrou
> Priority: Major
> Labels: pull-request-available
> Attachments: opt-level-conv.diff
>
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> Currently, when some Parquet nested data involves some repetition levels,
> converting the levels to bitmap goes through a slow scalar path unless the
> BMI2 instruction set is available and efficient (the latter using the PEXT
> instruction to process 16 levels at once).
> It may be possible to emulate PEXT for 5- or 6-bit masks by using a lookup
> table, allowing to process 5-6 levels at once.
> (also, it would be good to add nested reading benchmarks for non-trivial
> nesting; currently we only benchmark one-level struct and one-level list)
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