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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2269) PerformanceEvaluation "--nomapred" may assign duplicate random seed over multiple testing threads
Date Fri, 05 Mar 2010 17:26:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12841938#action_12841938
] 

stack commented on HBASE-2269:
------------------------------

@Tatsuya For sure super.hashCode() gives a different answer per instance of Test?  Thanks.

> PerformanceEvaluation "--nomapred" may assign duplicate random seed over multiple testing
threads
> -------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-2269
>                 URL: https://issues.apache.org/jira/browse/HBASE-2269
>             Project: Hadoop HBase
>          Issue Type: Bug
>          Components: test
>    Affects Versions: 0.20.3
>         Environment: Any operating system
>            Reporter: Tatsuya Kawano
>            Priority: Minor
>
> When you use PerformanceEvaluation with "--nomapred" option, you will end up having the
same random seeds assigned over multiple testing threads. So you'll get inaccurate results
from "random~~" tests.
> {code:title=PerformanceEvaluation.java}
> 542:  abstract class Test {
> 543:     protected final Random rand = new Random(System.currentTimeMillis());
> {code}
> Milliseconds won't be sufficient; today's JVM is much faster to create multiple Test
objects in one millisecond. You might want to use something like "{{super.hashCode()}}" instead.


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