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Posted to github@arrow.apache.org by "westonpace (via GitHub)" <gi...@apache.org> on 2023/07/11 23:07:49 UTC
[GitHub] [arrow] westonpace opened a new pull request, #36622: GH-36621: [C++] Added documentation for ACERO_ALIGNMENT_HANDLING
westonpace opened a new pull request, #36622:
URL: https://github.com/apache/arrow/pull/36622
### Rationale for this change
To document an existing environment variable that was not documented.
### What changes are included in this PR?
Adds a documentation section for this environment variable.
### Are these changes tested?
No, there are only docs.
### Are there any user-facing changes?
New documentation
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[GitHub] [arrow] github-actions[bot] commented on pull request #36622: GH-36621: [C++] Added documentation for ACERO_ALIGNMENT_HANDLING
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #36622:
URL: https://github.com/apache/arrow/pull/36622#issuecomment-1631619142
:warning: GitHub issue #36621 **has been automatically assigned in GitHub** to PR creator.
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[GitHub] [arrow] kou merged pull request #36622: GH-36621: [C++] Add documentation for ACERO_ALIGNMENT_HANDLING
Posted by "kou (via GitHub)" <gi...@apache.org>.
kou merged PR #36622:
URL: https://github.com/apache/arrow/pull/36622
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[GitHub] [arrow] kou commented on pull request #36622: GH-36621: [C++] Add documentation for ACERO_ALIGNMENT_HANDLING
Posted by "kou (via GitHub)" <gi...@apache.org>.
kou commented on PR #36622:
URL: https://github.com/apache/arrow/pull/36622#issuecomment-1635300791
http://crossbow.voltrondata.com/pr_docs/36622/cpp/env_vars.html
I'll merge this.
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[GitHub] [arrow] pitrou commented on a diff in pull request #36622: GH-36621: [C++] Add documentation for ACERO_ALIGNMENT_HANDLING
Posted by "pitrou (via GitHub)" <gi...@apache.org>.
pitrou commented on code in PR #36622:
URL: https://github.com/apache/arrow/pull/36622#discussion_r1262505508
##########
docs/source/cpp/env_vars.rst:
##########
@@ -26,6 +26,28 @@ Arrow C++ at runtime. Many of these variables are inspected only once per
process (for example, when the Arrow C++ DLL is loaded), so you cannot assume
that changing their value later will have an effect.
+.. envvar:: ACERO_ALIGNMENT_HANDLING
+
+ Arrow C++'s Acero module performs computation on streams of data. This
+ computation may involve a form of "type punning" that is technically
+ undefined behavior if the underlying array is not properly aligned. On
+ most modern CPUs this is not an issue, but some older CPUs may crash or
+ suffer poor performance. For this reason it is recommended that all
+ incoming array buffers are properly aligned.
+
+ The value of this environment variable controls what will happen when
+ Acero detects an unaligned buffer.
Review Comment:
```suggestion
Acero detects an unaligned buffer:
```
##########
docs/source/cpp/env_vars.rst:
##########
@@ -26,6 +26,28 @@ Arrow C++ at runtime. Many of these variables are inspected only once per
process (for example, when the Arrow C++ DLL is loaded), so you cannot assume
that changing their value later will have an effect.
+.. envvar:: ACERO_ALIGNMENT_HANDLING
+
+ Arrow C++'s Acero module performs computation on streams of data. This
+ computation may involve a form of "type punning" that is technically
+ undefined behavior if the underlying array is not properly aligned. On
+ most modern CPUs this is not an issue, but some older CPUs may crash or
+ suffer poor performance. For this reason it is recommended that all
+ incoming array buffers are properly aligned.
+
+ The value of this environment variable controls what will happen when
+ Acero detects an unaligned buffer.
+
+ - ``warn`` a warning is emitted
+ - ``ignore`` nothing, alignment checking is disabled
+ - ``reallocate`` the buffer is reallocated to a properly aligned address
+ - ``error`` the operation will fail with an error
Review Comment:
```suggestion
- ``warn``: a warning is emitted
- ``ignore``: nothing, alignment checking is disabled
- ``reallocate``: the buffer is reallocated to a properly aligned address
- ``error``: the operation fails with an error
```
##########
docs/source/cpp/env_vars.rst:
##########
@@ -26,6 +26,28 @@ Arrow C++ at runtime. Many of these variables are inspected only once per
process (for example, when the Arrow C++ DLL is loaded), so you cannot assume
that changing their value later will have an effect.
+.. envvar:: ACERO_ALIGNMENT_HANDLING
+
+ Arrow C++'s Acero module performs computation on streams of data. This
+ computation may involve a form of "type punning" that is technically
+ undefined behavior if the underlying array is not properly aligned. On
+ most modern CPUs this is not an issue, but some older CPUs may crash or
+ suffer poor performance. For this reason it is recommended that all
+ incoming array buffers are properly aligned.
Review Comment:
```suggestion
suffer poor performance. For this reason it is recommended that all
incoming array buffers are properly aligned, but some data sources
such as :ref:`Flight <flight-rpc>` may produce unaligned buffers.
```
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[GitHub] [arrow] github-actions[bot] commented on pull request #36622: GH-36621: [C++] Add documentation for ACERO_ALIGNMENT_HANDLING
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #36622:
URL: https://github.com/apache/arrow/pull/36622#issuecomment-1635190043
Revision: df536f33dd5fd02119b482f1a534543d21ec1e7f
Submitted crossbow builds: [ursacomputing/crossbow @ actions-ea9fff6db8](https://github.com/ursacomputing/crossbow/branches/all?query=actions-ea9fff6db8)
|Task|Status|
|----|------|
|preview-docs|[](https://github.com/ursacomputing/crossbow/actions/runs/5549953357/jobs/10134572104)|
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[GitHub] [arrow] kou commented on pull request #36622: GH-36621: [C++] Add documentation for ACERO_ALIGNMENT_HANDLING
Posted by "kou (via GitHub)" <gi...@apache.org>.
kou commented on PR #36622:
URL: https://github.com/apache/arrow/pull/36622#issuecomment-1635188287
@github-actions crossbow submit preview-docs
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[GitHub] [arrow] RichardHaythorn commented on pull request #36622: GH-36621: [C++] Add documentation for ACERO_ALIGNMENT_HANDLING
Posted by "RichardHaythorn (via GitHub)" <gi...@apache.org>.
RichardHaythorn commented on PR #36622:
URL: https://github.com/apache/arrow/pull/36622#issuecomment-1635499734
@westonpace I see it's already merged but it LGTM
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[GitHub] [arrow] conbench-apache-arrow[bot] commented on pull request #36622: GH-36621: [C++] Add documentation for ACERO_ALIGNMENT_HANDLING
Posted by "conbench-apache-arrow[bot] (via GitHub)" <gi...@apache.org>.
conbench-apache-arrow[bot] commented on PR #36622:
URL: https://github.com/apache/arrow/pull/36622#issuecomment-1647834700
After merging your PR, Conbench analyzed the 6 benchmarking runs that have been run so far on merge-commit 5037ab14f2a7686c38f6653b5f39ebe7feaf200f.
There were no benchmark performance regressions. 🎉
The [full Conbench report](https://github.com/apache/arrow/runs/15289655210) has more details. It also includes information about possible false positives for unstable benchmarks that are known to sometimes produce them.
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[GitHub] [arrow] westonpace commented on pull request #36622: GH-36621: [C++] Added documentation for ACERO_ALIGNMENT_HANDLING
Posted by "westonpace (via GitHub)" <gi...@apache.org>.
westonpace commented on PR #36622:
URL: https://github.com/apache/arrow/pull/36622#issuecomment-1631618892
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