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From Pavan K Narayanan <pavan.naraya...@gmail.com>
Subject Re: Mahout Collaborative Filtering using a parallel matrix factorization
Date Sat, 26 Oct 2013 06:38:07 GMT
can you kindly post sample of your input data. i am interested to see the
format of your csv file
On Oct 26, 2013 1:59 AM, "Brian Arnold" <barnold4238@gmail.com> wrote:

> Hey Everyone,
>
> I was hoping that someone could help me out with the
> ParallelALSFactoirzationJob that I am trying to run.  I have been trying to
> run this over a 27GB dataset of customer transaction data, and the job
> keeps failing with a null pointer exception. I am running with Mahout 0.8
> and the following parameters --lambda 0.05 --implicitFeedback true
> --numFeatures 20 --numIterations 1 --tempDir temp/mahout_als
> --numThreadsPerSolver 1.
> ParallelALSFactorizationJob-ItemRatingVectorsMapper-Reducer completes fine,
> ParallelALSFactorizationJob-TransposeMapper-Reducer completes fine,
> ParallelALSFactorizationJob-AverageRatingMapper-Reducer completes fine, but
> it fails on Recompute U, iteration (2/1), (1 threads, 5 features, implicit
> feedback).
>
>
> Here is the stacktrace I am receiving:
>
> java.lang.RuntimeException: java.lang.NullPointerException
>         at
> org.apache.hadoop.mapreduce.lib.map.MultithreadedMapper.run(MultithreadedMapper.java:149)
>         at
> org.apache.mahout.cf.taste.hadoop.als.MultithreadedSharingMapper.run(MultithreadedSharingMapper.java:53)
>         at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:763)
>         at org.apache.hadoop.mapred.MapTask.run(MapTask.java:363)
>         at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at javax.security.auth.Subject.doAs(Subject.java:396)
>         at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1232)
>         at org.apache.hadoop.mapred.Child.main(Child.java:249)
> Caused by: java.lang.NullPointerException
>         at
> org.apache.mahout.math.als.ImplicitFeedbackAlternatingLeastSquaresSolver.getYtransponseCuMinusIYPlusLambdaI(ImplicitFeedbackAlternatingLeastSquaresSolver.java:95)
>         at
> org.apache.mahout.math.als.ImplicitFeedbackAlternatingLeastSquaresSolver.solve(ImplicitFeedbackAlternatingLeastSquaresSolver.java:51)
>         at
> org.apache.mahout.cf.taste.hadoop.als.SolveImplicitFeedbackMapper.map(SolveImplicitFeedbackMapper.java:54)
>         at
> org.apache.mahout.cf.taste.hadoop.als.SolveImplicitFeedbackMapper.map(SolveImplicitFeedbackMapper.java:29)
>         at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
>         at
> org.apache.hadoop.mapreduce.lib.map.MultithreadedMapper$MapRunner.run(MultithreadedMapper.java:268)
>
>
> Thanks so much!
>
> Brian
>

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