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https://issues.apache.org/jira/browse/MAHOUT-577?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12979528#action_12979528
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Maya Hristakeva commented on MAHOUT-577:
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The size of the original matrix is 150k x 200x, and is very sparse (it finally
managed to complete after a few days). However, the compressed LDA matrix
although having a size of only 150k x 5 is a dense matrix. I left the job
running over the weekend with some stdout, and it is still mapping
co-occurrence pairs (~11 billion or so). I have now identified that the problem
is the density of the matrix. The same problem occurs if you compress the
original matrix with SVD (aka LSA) which generates a similar to LDA tall dense
matrix, and then try to compute the row-similarity.
@Sean: We do have a decent size cluster, and since there are 5 columns in the
matrix the job ended up with only 5 working mappers. I'll try optimizing the
sort parameters. I believe we already use a sort factor of 100 but would
double-check just in case.
I won't get a chance to re-run the job until later in the week, but I'll let
you know if optimizing the sort factors helps. If not, I'll need to implement
something that deals with tall dense matrices, especially since 150k rows is
only a small fraction of your dataset.
Thanks everyone,
Maya
> RowSimilarityJob hangs during CooccurrencesMapper
> -------------------------------------------------
>
> Key: MAHOUT-577
> URL: https://issues.apache.org/jira/browse/MAHOUT-577
> Project: Mahout
> Issue Type: Bug
> Components: Collaborative Filtering
> Affects Versions: 0.4
> Environment: Linux Debian 5.0.5, 12GB Ram, Hadoop 20.3 installation
> Reporter: Maya Hristakeva
> Fix For: 0.5
>
>
> Hello,
> When trying to run a RowSimilarityJob on a matrix ( 146682 x 138351 ), the
> job gets through the RowWeightMapper and WeightedOccurrencesPerColumnReducer,
> and hangs during the CooccurrencesMapper although it shows that the map tasks
> are 100% complete.
> The command I use to run the job is:
> hadoop jar mahout-core-0.4-job.jar
> org.apache.mahout.math.hadoop.similarity.RowSimilarityJob
> -Dmapred.input.dir=/user/maya.hristakeva/mahout/core4/tf/1/0.001/title/12_07_10/lda/5/lda-sim/ldaCompressedDocumentsMatrix
>
> -Dmapred.output.dir=/user/maya.hristakeva/mahout/core4/tf/1/0.001/title/12_07_10/lda/5/lda-sim/ldaDocumentSimilarityMatrix
> -Dmapred.reduce.tasks=8 -Dmapred.map.tasks=200
> -Dmapred.job.name=LDA_ROW_SIMILARITY_TEST --tempDir
> /user/maya.hristakeva/temp/lda/5 --numberOfColumns 138351
> --similarityClassname
> org.apache.mahout.math.hadoop.similarity.vector.DistributedEuclideanDistanceVectorSimilarity
> --maxSimilaritiesPerRow 10
> And the output of the mappers which are 100% complete, but hanging is:
> syslog logs
> 01-05 18:30:00,835 INFO org.apache.hadoop.mapred.MapTask: bufstart =
> 29085149; bufend = 39038598; bufvoid = 99614720
> 2011-01-05 18:30:00,835 INFO org.apache.hadoop.mapred.MapTask: kvstart =
> 65461; kvend = 327605; length = 327680
> 2011-01-05 18:30:06,241 INFO org.apache.hadoop.mapred.MapTask: Finished spill
> 94
> 2011-01-05 18:30:09,208 INFO org.apache.hadoop.mapred.MapTask: Spilling map
> output: record full = true
> 2011-01-05 18:30:09,208 INFO org.apache.hadoop.mapred.MapTask: bufstart =
> 39038598; bufend = 48983989; bufvoid = 99614720
> 2011-01-05 18:30:09,208 INFO org.apache.hadoop.mapred.MapTask: kvstart =
> 327605; kvend = 262068; length = 327680
> 2011-01-05 18:30:14,528 INFO org.apache.hadoop.mapred.MapTask: Finished spill
> 95
> 2011-01-05 18:30:17,328 INFO org.apache.hadoop.mapred.MapTask: Spilling map
> output: record full = true
> 2011-01-05 18:30:17,328 INFO org.apache.hadoop.mapred.MapTask: bufstart =
> 48983989; bufend = 58929384; bufvoid = 99614720
> 2011-01-05 18:30:17,328 INFO org.apache.hadoop.mapred.MapTask: kvstart =
> 262068; kvend = 196531; length = 327680
> 2011-01-05 18:30:22,615 INFO org.apache.hadoop.mapred.MapTask: Finished spill
> 96
> .
> .
> .
> This problem does not occur when I use a toy matrix of 100 x 100, but once I
> give it the original matrix of ..... the problem is always reproducible.
> Any ideas on what could be causing this?
> Thanks,
> Maya Hristakeva
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