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From Nico Higgs <elha...@gmail.com>
Subject Taste and MySQL with GroupLens dataset
Date Wed, 29 Jul 2009 20:56:20 GMT
Hi Sean and everybody!

I've download Mahout from SVN and followed the FAQ for trying Taste with the
1M ratings from GroupLens dataset test. First I tried With the
GroupLensRecommender(that uses a FileDataModel) and everythings went ok.

Then I decide to give a try with the data loaded on MySQL with the Slopone
Recommender. After inserting the ratings.dat in taste_preferences table
(1000029 rows), and the first run (3 hours and a half to generate the
4922072 rows for the slopeone diffs), I tried to get a recommend but a I'm
getting this error in
the getDiffs method of AbstractJDBCDiffStorage (with the userID=1 and
howMany=5)

Caused by: java.lang.ArrayIndexOutOfBoundsException: 53
    at
org.apache.mahout.cf.taste.impl.recommender.slopeone.jdbc.AbstractJDBCDiffStorage.getDiffs(AbstractJDBCDiffStorage.java:175)
    at
org.apache.mahout.cf.taste.impl.recommender.slopeone.SlopeOneRecommender.doEstimatePreference(SlopeOneRecommender.java:136)
    at
org.apache.mahout.cf.taste.impl.recommender.slopeone.SlopeOneRecommender.access$100(SlopeOneRecommender.java:50)
    at
org.apache.mahout.cf.taste.impl.recommender.slopeone.SlopeOneRecommender$Estimator.estimate(SlopeOneRecommender.java:219)
    at
org.apache.mahout.cf.taste.impl.recommender.slopeone.SlopeOneRecommender$Estimator.estimate(SlopeOneRecommender.java:209)


Looking at the code it seems, that the set containg the results of the
diffSQL contains distinct or more data than the preferences of the user. Is
this possible?

Thanks and regards!

PD: I'm currently starting with taste so I don't know If i could give any
more help. Nevetherless I will continue to investigate further the problem
and tell you If I found something.

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