[jira] [Commented] (MAPREDUCE-4827) Increase hash quality of HashPartitioner

["Hadoop QA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13510911#comment-13510911 ] 

Hadoop QA commented on MAPREDUCE-4827:
--------------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12555191/betterhash1.txt
  against trunk revision .

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:red}-1 tests included{color}.  The patch doesn't appear to include any new or modified tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    {color:red}-1 javac{color:red}.  The patch appears to cause the build to fail.

Console output: https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3097//console

This message is automatically generated.
                
> Increase hash quality of HashPartitioner
> ----------------------------------------
>
>                 Key: MAPREDUCE-4827
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4827
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>            Reporter: Radim Kolar
>         Attachments: betterhash1.txt
>
>
> hash partitioner is using object.hashCode() for splitting keys into partitions. This results in bad distributions because hashCode() quality is poor. 
> These hashCode() functions are sometimes written by hand (very poor quality) and sometimes generated from by commons lang code (poor quality). Applying some transformation on top of hashCode() provides better distribution.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira