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Date: Mon, 20 Jun 2011 20:12:48 +0000 (UTC)
From: "monica beckwith (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
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Subject: [jira] [Updated] (HADOOP-7401) Unit test TestPureJavaCRC32 warmup
 code warms up the not-so-important loop in PureJavaCRC32.update()
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     [ https://issues.apache.org/jira/browse/HADOOP-7401?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

monica beckwith updated HADOOP-7401:
------------------------------------

    Status: Patch Available  (was: Open)

> Unit test TestPureJavaCRC32 warmup code warms up the not-so-important loop in PureJavaCRC32.update()
> ----------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-7401
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7401
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: test
>    Affects Versions: 0.21.0
>         Environment: Solaris-Sparcv9; Solaris-AMD64
>            Reporter: monica beckwith
>            Assignee: monica beckwith
>            Priority: Minor
>             Fix For: 0.21.0
>
>         Attachments: hadoop-7401.patch
>
>   Original Estimate: 1m
>  Remaining Estimate: 1m
>
> When the warmup code sequence in TestPureJavaCRC32.java is executed, it sends size=len=2 and due to the value of 'trials' in for loop in doBench(), the crc.update() gets run > the compile threshold, thus providing the information that 'while 0<len<7' is a hot loop and 'while len>7' is a cold loop. This brings the MB/s number for len > 7 in PureJavaCRC32.update() way down (e.g. ~28.5% for size=len=65536).
> The workaround would be to use size=len=>7 (so just having size=len=2101 ahead of size=len=2 will do the trick) in the warmup section. 

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