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Posted to dev@mahout.apache.org by "Sebastian Schelter (JIRA)" <ji...@apache.org> on 2010/08/13 08:13:17 UTC
[jira] Commented: (MAHOUT-475) Replace Mapper with
MultithreadedMapper to implement
org.apache.mahout.math.hadoop.similarity.RowSimilarityJob.CooccurrencesMapper
[ https://issues.apache.org/jira/browse/MAHOUT-475?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898100#action_12898100 ]
Sebastian Schelter commented on MAHOUT-475:
-------------------------------------------
Hui,
Just like in the other issue can you follow these steps:
# Modify your local copy of mahout to include the changes you propose
# build Mahout and run your job again with your modified version
# upload a patch containing your changes and give us some details on the performance increase you encountered
Have a look at this website: https://cwiki.apache.org/confluence/display/MAHOUT/How+To+Contribute
> Replace Mapper with MultithreadedMapper to implement org.apache.mahout.math.hadoop.similarity.RowSimilarityJob.CooccurrencesMapper
> ------------------------------------------------------------------------------------------------------------------------------------
>
> Key: MAHOUT-475
> URL: https://issues.apache.org/jira/browse/MAHOUT-475
> Project: Mahout
> Issue Type: Improvement
> Components: Collaborative Filtering
> Affects Versions: 0.4
> Reporter: Han Hui Wen
> Fix For: 0.4
>
>
> Because CooccurrencesMapper has huge computing,
> Maybe we can replace Mapper with MultithreadedMapper.
> Original:
> {code}
> public static class CooccurrencesMapper
> extends Mapper<VarIntWritable,WeightedOccurrenceArray,WeightedRowPair,Cooccurrence>
> {code}
> new:
> {code}
> public static class CooccurrencesMapper
> extends MultithreadedMapper<VarIntWritable,WeightedOccurrenceArray,WeightedRowPair,Cooccurrence>
> {code}
> And call the mapper
> original:
> {code}
> if (shouldRunNextPhase(parsedArgs, currentPhase)) {
> Job pairwiseSimilarity = prepareJob(weightsPath,
> pairwiseSimilarityPath,
> SequenceFileInputFormat.class,
> CooccurrencesMapper.class,
> WeightedRowPair.class,
> Cooccurrence.class,
> SimilarityReducer.class,
> SimilarityMatrixEntryKey.class,
> MatrixEntryWritable.class,
> SequenceFileOutputFormat.class);
> Configuration pairwiseConf = pairwiseSimilarity.getConfiguration();
> pairwiseConf.set(DISTRIBUTED_SIMILARITY_CLASSNAME, distributedSimilarityClassname);
> pairwiseConf.setInt(NUMBER_OF_COLUMNS, numberOfColumns);
> pairwiseSimilarity.waitForCompletion(true);
> }
> {code}
> new:
> {code}
> if (shouldRunNextPhase(parsedArgs, currentPhase)) {
> Job pairwiseSimilarity = prepareJob(weightsPath,
> pairwiseSimilarityPath,
> SequenceFileInputFormat.class,
> CooccurrencesMapper.class,
> WeightedRowPair.class,
> Cooccurrence.class,
> SimilarityReducer.class,
> SimilarityMatrixEntryKey.class,
> MatrixEntryWritable.class,
> SequenceFileOutputFormat.class);
> Configuration pairwiseConf = pairwiseSimilarity.getConfiguration();
> pairwiseConf.set(DISTRIBUTED_SIMILARITY_CLASSNAME, distributedSimilarityClassname);
> pairwiseConf.setInt(NUMBER_OF_COLUMNS, numberOfColumns);
> CooccurrencesMapper.setNumberOfThreads(n); //n should about be less the core counts of the machine.
> pairwiseSimilarity.waitForCompletion(true);
>
> }
> {code}
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