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From "Razon, Oren" <oren.ra...@intel.com>
Subject Using ALS job to extract the decomposed matrices
Date Tue, 26 Feb 2013 20:05:04 GMT
Hi there,
I'm using Hadoop-core 0.20.3 and I want to use mahout ALS algorithm.
My purpose is to run the ALS model and extract the decomposed matrices for further usage in
my application (I want to create 2 different csv files: [UserId, latentFeatureId, Value] and
[ItemId, latentFeatureId, Value]).
I found that in Mahout0.6\7 I have the ALSUtils class who can help me extract this info.
However when I just try to execute a simple movielens example by executing the "ParallelALS..."
job I get the error below. I found it strange cause when executing the exact same job on mahout
0.5 it works fine. Any thoughts? What differences exist between the version (and relevant
to ALS) which can cause it?

In addition, if I will use Mahout 0.5 eventually, can u advise me how can I extract the decomposed
matrices data so I could build my csv's?

Thanks,
Oren

13/02/26 04:31:27 INFO als.ParallelALSFactorizationJob: Recomputing U (iteration 0/1)
13/02/26 04:31:34 INFO input.FileInputFormat: Total input paths to process : 1
13/02/26 04:31:34 INFO mapred.JobClient: Running job: job_201302081356_0543
13/02/26 04:31:35 INFO mapred.JobClient:  map 0% reduce 0%
13/02/26 04:31:50 INFO mapred.JobClient:  map 1% reduce 0%
13/02/26 04:31:53 INFO mapred.JobClient: Task Id : attempt_201302081356_0543_m_000000_0, Status
: FAILED
java.lang.NullPointerException
      at org.apache.mahout.math.als.AlternatingLeastSquaresSolver.createMiIi(AlternatingLeastSquaresSolver.java:73)
      at org.apache.mahout.math.als.AlternatingLeastSquaresSolver.solve(AlternatingLeastSquaresSolver.java:45)
      at org.apache.mahout.cf.taste.hadoop.als.ParallelALSFactorizationJob$SolveExplicitFeedbackMapper.map(ParallelALSFacto
      at org.apache.mahout.cf.taste.hadoop.als.ParallelALSFactorizationJob$SolveExplicitFeedbackMapper.map(ParallelALSFacto
      at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
      at org.apache.hadoop.mapred.MapTask.runNewMapper_aroundBody4(MapTask.java:813)
      at org.apache.hadoop.mapred.MapTask$AjcClosure5.run(MapTask.java:1)
      at org.aspectj.runtime.reflect.JoinPointImpl.proceed(JoinPointImpl.java:149)
      at com.intel.bigdata.management.agent.HadoopTaskAspect.doPhaseCall(HadoopTaskAspect.java:166)
      at com.intel.bigdata.management.agent.HadoopTaskAspect.ajc$inlineAccessMethod$com_intel_bigdata_management_agent_


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