[jira] [Updated] (ARROW-10058) [C++] Investigate performance of LevelsToBitmap without BMI2

["Yibo Cai (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-10058?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yibo Cai updated ARROW-10058:
-----------------------------
    Attachment: opt-level-conv.diff

> [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
>            Priority: Major
>         Attachments: opt-level-conv.diff
>
>
> 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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