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Date: Mon, 7 Sep 2009 07:46:57 -0700 (PDT)
From: "Hudson (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-288) Redundant computation in hashCode()
 implemenation
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    [ https://issues.apache.org/jira/browse/HDFS-288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12752152#action_12752152 ] 

Hudson commented on HDFS-288:
-----------------------------

Integrated in Hadoop-Hdfs-trunk #75 (See [http://hudson.zones.apache.org/hudson/job/Hadoop-Hdfs-trunk/75/])
    . Redundant computation in hashCode() implementation. Contributed by Tsz Wo (Nicholas), SZE.


> Redundant computation in hashCode() implemenation
> -------------------------------------------------
>
>                 Key: HDFS-288
>                 URL: https://issues.apache.org/jira/browse/HDFS-288
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>             Fix For: 0.21.0
>
>         Attachments: h288_20090820.patch
>
>
> In some hashCode() implementation (e.g. Block.hashCode()), the formula has the form
> {noformat}
> 37 * 17 + f(x),
> {noformat}
> where f( x ) is some function.  Adding 37*17 to f( x ) shifts the value of f( x ).  It is not effective to do shifting in hash functions.  The computation is redundant.

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