[jira] [Resolved] (ARROW-8129) [C++][Compute] Refine compare sorting kernel

["Antoine Pitrou (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-8129?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Antoine Pitrou resolved ARROW-8129.
-----------------------------------
    Fix Version/s: 0.17.0
       Resolution: Fixed

Issue resolved by pull request 6640
[https://github.com/apache/arrow/pull/6640]

> [C++][Compute] Refine compare sorting kernel
> --------------------------------------------
>
>                 Key: ARROW-8129
>                 URL: https://issues.apache.org/jira/browse/ARROW-8129
>             Project: Apache Arrow
>          Issue Type: Improvement
>            Reporter: Yibo Cai
>            Assignee: Yibo Cai
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 0.17.0
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> Sorting kernel implements two comparison functions, [CompareValues|https://github.com/apache/arrow/blob/ab21f0ee429c2a2c82e4dbc5d216ab1da74221a2/cpp/src/arrow/compute/kernels/sort_to_indices.cc#L67] use array.Value() for numeric data and [CompareViews|https://github.com/apache/arrow/blob/ab21f0ee429c2a2c82e4dbc5d216ab1da74221a2/cpp/src/arrow/compute/kernels/sort_to_indices.cc#L72] uses array.GetView() for non-numeric ones. It can be simplified by using GetView() only as all data types support GetView().
> To my surprise, benchmark shows about 40% performance improvement after the change.
> After some digging, I find in current code, the [comparison callback|https://github.com/apache/arrow/blob/ab21f0ee429c2a2c82e4dbc5d216ab1da74221a2/cpp/src/arrow/compute/kernels/sort_to_indices.cc#L94] is not inlined (check disassembled code), it leads to a function call. It's very bad for this hot loop. Using only GetView() fixes this issue, code inlined okay.



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