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Posted to issues@arrow.apache.org by "Wes McKinney (JIRA)" <ji...@apache.org> on 2018/12/01 15:13:00 UTC

[jira] [Commented] (ARROW-3922) [C++] improve the performance of bitmap operations

    [ https://issues.apache.org/jira/browse/ARROW-3922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16705865#comment-16705865 ] 

Wes McKinney commented on ARROW-3922:
-------------------------------------

This seems to produce smaller code on MSVC as well as gcc/clang

https://godbolt.org/z/sFcSP6

> [C++] improve the performance of bitmap operations
> --------------------------------------------------
>
>                 Key: ARROW-3922
>                 URL: https://issues.apache.org/jira/browse/ARROW-3922
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Animesh Trivedi
>            Assignee: Animesh Trivedi
>            Priority: Major
>
> C++ bitmap code can be optimized further by using the unsigned integers than "int64_t" for bitmap checks, and eliminating the kBitmap. See here [https://godbolt.org/z/deq0_q] - compare the size of the assembly code. And the performance measurements in the blog show up to 50% performance gains. 
> Alternatively if signed to unsigned upgrade is not possible (perhaps in every language), then in the C++ code, we should use the bitmap operations directory ( `<<3` for division by 8, and ` & 0x7` for modulo by 8 operation), instead of `/` and `%`. 



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