[jira] [Commented] (ARROW-10321) [C++] Building AVX512 code when we should not

["Sanchit Jain (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-10321?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17251314#comment-17251314 ] 

Sanchit Jain commented on ARROW-10321:
--------------------------------------

Unrelated to this issue, but why does the current build process use AVX2 as the default SIMD level, even if AVX-512 is supported on a machine?

> [C++] Building AVX512 code when we should not
> ---------------------------------------------
>
>                 Key: ARROW-10321
>                 URL: https://issues.apache.org/jira/browse/ARROW-10321
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++
>            Reporter: Neal Richardson
>            Assignee: Frank Du
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 3.0.0
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> On https://github.com/autobrew/homebrew-core/pull/31, where we are packaging Arrow for an old macOS SDK version, we found what I believe are 2 different problems:
> 1. The check for AVX512 support was returning true when in fact the compiler did not support it
> 2. Even when we manually set the runtime SIMD level to less-than-AVX512, it was still trying to compile one of the AVX512 files, which failed. I added a patch that made that file conditional, but there's probably a proper cmake way to tell it not to compile that file at all
> cc [~yibo] [~apitrou]



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