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https://issues.apache.org/jira/browse/MAHOUT-353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12851581#action_12851581
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Rajat Tibrewal commented on MAHOUT-353:
---------------------------------------
columnVector is initialized in the CooccurrenceCache constructor which in turn
in invoked in the configure() of RecommenderMapper at line 90 and used later as
"retriever" in cooccurrencecache (which is of type Cache).
So assuming that configure() IS invoked (without which columnVector wont be
initialized), your observation of "not able to load a column vector that was
previously generated" can be possibly inspected at the invocation of:
cooccurrenceColumnCache = new Cache<IntWritable,Vector>(new
CooccurrenceCache(cooccurrenceColumnMap), 100);
Maybe decoupling this statement as below might help:
cocache = new CooccurrenceCache(cooccurrenceColumnMap);
cooccurrenceColumnCache = new Cache<IntWritable,Vector>(cooccurencecache, 100);
where cocache be a class variable of RecommenderMapper of type
CooccurrenceCache.
Again, this is just a hunch! Sorry to disturb if it doesnt work :)
> java.lang.NullPointerException in RecommenderMapper
> ---------------------------------------------------
>
> Key: MAHOUT-353
> URL: https://issues.apache.org/jira/browse/MAHOUT-353
> Project: Mahout
> Issue Type: Bug
> Components: Collaborative Filtering
> Affects Versions: 0.4
> Reporter: Hui Wen Han
> Fix For: 0.4
>
>
> java.lang.NullPointerException
> at
> org.apache.mahout.cf.taste.hadoop.item.RecommenderMapper$CooccurrenceCache.get(RecommenderMapper.java:169)
> at
> org.apache.mahout.cf.taste.hadoop.item.RecommenderMapper$CooccurrenceCache.get(RecommenderMapper.java:154)
> at
> org.apache.mahout.cf.taste.impl.common.Cache.getAndCacheValue(Cache.java:125)
> at org.apache.mahout.cf.taste.impl.common.Cache.get(Cache.java:94)
> at
> org.apache.mahout.cf.taste.hadoop.item.RecommenderMapper.map(RecommenderMapper.java:111)
> at
> org.apache.mahout.cf.taste.hadoop.item.RecommenderMapper.map(RecommenderMapper.java:52)
> at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
> at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:358)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:307)
> at org.apache.hadoop.mapred.Child.main(Child.java:170)
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