I’m using ALS with spark 1.0.0, the code should be:
https://github.com/apache/spark/blob/branch-1.0/mllib/src/main/scala/org/apache/spark/mllib/recommendation/ALS.scala

I think the following two method should produce the same (or near) result:

MatrixFactorizationModel model = ALS.train(ratings.rdd(), 30, 30, 0.01, -1,
1);
MatrixFactorizationModel model = ALS.trainImplicit(ratings.rdd(), 30, 30,
0.01, -1, 0, 1);


the data I used is display log, the format of log is as following:

user  item  if-click


I use 1.0 as score for click pair, and 0 as score for non-click pair.

 in the second method, the alpha is set to zero, so the confidence for
positive and negative are both 1.0 (right?)

I think the two method should produce similar result, but the result is : 
the second method’s result is very bad (the AUC of the first result is 0.7,
but the AUC of the second result is only 0.61)


I could not understand why, could you help me?


Thank you very much!




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