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https://issues.apache.org/jira/browse/HAMA-904?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Illecker updated HAMA-904:
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Assignee: (was: Martin Illecker)
> Fix Collaborative Filtering Example
> -----------------------------------
>
> Key: HAMA-904
> URL: https://issues.apache.org/jira/browse/HAMA-904
> Project: Hama
> Issue Type: Bug
> Components: examples, machine learning
> Affects Versions: 0.6.4
> Reporter: Martin Illecker
> Priority: Minor
> Labels: collaborative-filtering, examples, machine_learning
> Fix For: 0.7.0
>
>
> *Fix Collaborative Filtering Example and revise test case.*
> I had a deep look into the collaborative filtering example of Ikhtiyor
> Ahmedov \[1] and found the following questions / problems:
> - Why are user and item features broadcasted \[2] by each peer and not
> shared by a global input file on HDFS? (possible performance increase?)
> - Use o.a.h.c.u.KeyValuePair instead of commons.math3.util.Pair in
> UserSimilarity \[3] and ItemSimilarity \[4]
> - No need for normalizeWithBroadcastingValues \[5] when taskNum = 1
> - Why are values sent to itself and received later? \[6] (possible
> performance increase?)
> - Why is every task saving all items? \[7] (duplicate saves?)
> - Why is the default ALPHA value 0.01 and not 0.001? \[8] (if (matrixRank >
> 250) -> Infinite / NaN)
> I hope Ikhtiyor Ahmedov will finally become a committer and helps us to solve
> these questions.
> Thanks!
> \[1] https://issues.apache.org/jira/browse/HAMA-612
> \[2]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/recommendation/cf/OnlineTrainBSP.java#L116-128
> \[3]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/recommendation/UserSimilarity.java#L22
> \[4]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/recommendation/ItemSimilarity.java#L22
> \[5]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/recommendation/cf/OnlineTrainBSP.java#L138
> \[6]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/recommendation/cf/OnlineTrainBSP.java#L323
> \[7]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/recommendation/cf/OnlineTrainBSP.java#L387-422
> \[8]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/recommendation/cf/function/MeanAbsError.java#L62
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