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https://issues.apache.org/jira/browse/HAMA-458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13135602#comment-13135602
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Edward J. Yoon commented on HAMA-458:
-------------------------------------
{code}
11/10/26 09:52:42 FATAL bsp.BSPPeerImpl: Caught exception during superstep 0!
java.lang.RuntimeException: java.lang.InstantiationException
at
org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
at org.apache.hama.bsp.BSPPeerImpl.sync(BSPPeerImpl.java:195)
at
org.apache.hama.examples.PiEstimator$MyEstimator.bsp(PiEstimator.java:70)
at org.apache.hama.bsp.BSPTask.run(BSPTask.java:62)
at
org.apache.hama.bsp.GroomServer$BSPPeerChild.main(GroomServer.java:946)
Caused by: java.lang.InstantiationException
at
sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:30)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at
org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:113)
... 4 more
{code}
Found a bug. I'm fixing directly.
> Add Combiners
> -------------
>
> Key: HAMA-458
> URL: https://issues.apache.org/jira/browse/HAMA-458
> Project: Hama
> Issue Type: New Feature
> Components: bsp
> Affects Versions: 0.3.0
> Reporter: Thomas Jungblut
> Assignee: Edward J. Yoon
> Fix For: 0.4.0
>
> Attachments: combiner_v01.patch, combiner_v02.patch,
> combiner_v03.patch
>
>
> We have spoken about it on the mailing list:
> http://www.mail-archive.com/[email protected]/msg05540.html
> Small extract:
> {quote}
> When should the combiner be called and in which form. In MapReduce they
> are plain reducers, so we can have the same model but not grouped by a key
> rather than the class name of the message.
> {quote}
> Especially if we could collect all task data on the same host and combine
> them. This would yield into better performance.
> We need a smart idea.
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