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https://issues.apache.org/jira/browse/MAHOUT-475?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Han Hui Wen  updated MAHOUT-475:
--------------------------------

    Attachment: patch_985097.txt

Patch :
1) using MultithreadedMapper
2) compress the  output
3) add --numMapThreads parameter
4) add -Dmapred.reduce.tasks

> Replace Mapper with  MultithreadedMapper  to run job pairwiseSimilarity 
> ------------------------------------------------------------------------
>
>                 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
>
>         Attachments: patch_985097.txt
>
>
> Because CooccurrencesMapper has huge computing,
> Maybe we can replace  Mapper with  MultithreadedMapper.
> 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);
>       MultithreadedMapper.setMapperClass(pairwiseSimilarity, 
> CooccurrencesMapper.class);
>       MultithreadedMapper.setNumberOfThreads(pairwiseSimilarity, 
> numMapThreads);
>       SequenceFileOutputFormat.setCompressOutput(pairwiseSimilarity, true);
>       SequenceFileOutputFormat.setOutputCompressorClass(pairwiseSimilarity, 
> GzipCodec.class);
>       SequenceFileOutputFormat.setOutputCompressionType(pairwiseSimilarity, 
> CompressionType.BLOCK);
>       pairwiseSimilarity.waitForCompletion(true);
>     }
> {code}

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