org.apache.mahout.cf.taste.hadoop.pseudo.RecommenderJob breaks when no
usersFile is supplied
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Key: MAHOUT-386
URL: https://issues.apache.org/jira/browse/MAHOUT-386
Project: Mahout
Issue Type: Bug
Components: Collaborative Filtering
Reporter: Sebastian Schelter
When one tries to run org.apache.mahout.cf.taste.hadoop.pseudo.RecommenderJob
without a usersFile (the file containing the userIDs to generate
recommendations for) it throws an Exception in the Reducer.
I took a look at the code and it seems that there are some needless things done:
org.apache.mahout.cf.taste.hadoop.pseudo.RecommenderReducer tries to create a
set of userIDs to generate recommendations for and fails to do this if no
usersFile is supplied, when it tries to parse the preferences file. As far as I
understand the code the Mapper already maps out only the userIDs to generate
recommendations for, so there the check in the reducer is not even necessary,
right? Correct me if I'm wrong.
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How to reproduce the error:
1) Create a file containing some sample preferences and call it
mahout-testing.txt, mine looks like this
1,2,1
1,3,2
2,1,1
2,3,1
2) Run the Job without a usersFile, e.g.:
hadoop jar core/target/mahout-core-0.4-SNAPSHOT.job
org.apache.mahout.cf.taste.hadoop.pseudo.RecommenderJob
-Dmapred.input.dir=./mahout-testing.txt -Dmapred.output.dir=/tmp/mahout/out
--tempDir /tmp/mahout/tmp --recommenderClassName
org.apache.mahout.cf.taste.impl.recommender.GenericItemBasedRecommender
java.lang.RuntimeException: Error in configuring object
at
org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:93)
at
org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:64)
at
org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:117)
at
org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:426)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:411)
at
org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:215)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at
org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:88)
... 5 more
Caused by: java.lang.NumberFormatException: For input string: "1,2,1"
at
java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Long.parseLong(Long.java:419)
at java.lang.Long.parseLong(Long.java:468)
at
org.apache.mahout.cf.taste.hadoop.pseudo.RecommenderReducer.configure(RecommenderReducer.java:88)
... 10 more
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