[
https://issues.apache.org/jira/browse/ARROW-764?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16290264#comment-16290264
]
ASF GitHub Bot commented on ARROW-764:
--------------------------------------
seibs opened a new pull request #1422: WIP ARROW-764: [C++] Improves
performance of CopyBitmap and adds benchmarks
URL: https://github.com/apache/arrow/pull/1422
I took a swing at improving the CopyBitmap performance (benchmarks below).
I'm a C/C++ novice, so I thought I'd get some feedback before I went too much
further.
**Starting Point**
```
Run on (4 X 2208 MHz CPU s)
12/13/17 21:15:18
Benchmark Time CPU
Iterations
------------------------------------------------------------------------------
BM_CopyBitmap/97.6563k/0/min_time:1.000 4779 us 4758 us
289 20.0445MB/s
BM_CopyBitmap/976.563k/0/min_time:1.000 47740 us 47476 us
26 20.0875MB/s
BM_CopyBitmap/97.6563k/4/min_time:1.000 4858 us 4866 us
289 19.5991MB/s
BM_CopyBitmap/976.563k/4/min_time:1.000 48117 us 47953 us
29 19.8879MB/s
```
**Using stanford bithacks for SetBitTo**
```
Run on (4 X 2208 MHz CPU s)
12/13/17 21:22:05
Benchmark Time CPU
Iterations
------------------------------------------------------------------------------
BM_CopyBitmap/97.6563k/0/min_time:1.000 1647 us 1649 us
815 57.8415MB/s
BM_CopyBitmap/976.563k/0/min_time:1.000 16368 us 16397 us
81 58.1629MB/s
BM_CopyBitmap/97.6563k/4/min_time:1.000 1599 us 1610 us
815 59.2186MB/s
BM_CopyBitmap/976.563k/4/min_time:1.000 16026 us 16011 us
81 59.5644MB/s
```
**memcpy + shifting**
*This solution provides varying performance depending on whether or not the
bit offset is a multiple of 8*
```
Run on (4 X 2208 MHz CPU s)
12/13/17 21:23:44
Benchmark Time CPU
Iterations
------------------------------------------------------------------------------
BM_CopyBitmap/97.6563k/0/min_time:1.000 5 us 5 us
280000 18.9651GB/s
BM_CopyBitmap/976.563k/0/min_time:1.000 62 us 61 us
22400 15.1721GB/s
BM_CopyBitmap/97.6563k/4/min_time:1.000 171 us 170 us
6892 560.872MB/s
BM_CopyBitmap/976.563k/4/min_time:1.000 1639 us 1639 us
896 581.782MB/s
```
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> [C++] Improve performance of CopyBitmap, add benchmarks
> -------------------------------------------------------
>
> Key: ARROW-764
> URL: https://issues.apache.org/jira/browse/ARROW-764
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Wes McKinney
> Labels: pull-request-available
> Fix For: 0.9.0
>
>
> This is follow up work after a discussion in the patch for ARROW-657
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