[ 
https://issues.apache.org/jira/browse/ARROW-1942?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16369669#comment-16369669
 ] 

ASF GitHub Bot commented on ARROW-1942:
---------------------------------------

wesm commented on issue #1551: ARROW-1942: [C++] Hash table specializations for 
small integers
URL: https://github.com/apache/arrow/pull/1551#issuecomment-366853886
 
 
   @xuepanchen I added a template for the 8 bit hash function to avoid 
arithmetic in the uint8 case
   
   before this change:
   
   ```
   $ ./release/compute-benchmark --benchmark_filter=UInt8
   Run on (8 X 4399.69 MHz CPU s)
   2018-02-19 21:57:13
   Benchmark                                                         Time       
    CPU Iterations
   
-----------------------------------------------------------------------------------------------
   BM_UniqueUInt8NoNulls/16M/200/min_time:1.000/real_time         8339 us       
8339 us        166   1.87372GB/s
   BM_UniqueUInt8WithNulls/16M/200/min_time:1.000/real_time      28536 us      
28537 us         49     560.7MB/s
   ```
   
   after this change:
   
   ```
   $ ./release/compute-benchmark --benchmark_filter=UInt8
   Run on (8 X 4400 MHz CPU s)
   2018-02-19 21:55:51
   Benchmark                                                         Time       
    CPU Iterations
   
-----------------------------------------------------------------------------------------------
   BM_UniqueUInt8NoNulls/16M/200/min_time:1.000/real_time         7749 us       
7749 us        180   2.01641GB/s
   BM_UniqueUInt8WithNulls/16M/200/min_time:1.000/real_time      28042 us      
28042 us         50   570.571MB/s
   ```

----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org


> [C++] Hash table specializations for small integers
> ---------------------------------------------------
>
>                 Key: ARROW-1942
>                 URL: https://issues.apache.org/jira/browse/ARROW-1942
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Wes McKinney
>            Assignee: Panchen Xue
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 0.9.0
>
>
> There is no need to use a dynamically-sized hash table with uint8, int8, 
> since a fixed-size lookup table can be used and avoid hashing altogether



--
This message was sent by Atlassian JIRA
(v7.6.3#76005)

Reply via email to