NullPointerException while using MixedGradient with SGD algorithm
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Key: MAHOUT-678
URL: https://issues.apache.org/jira/browse/MAHOUT-678
Project: Mahout
Issue Type: Bug
Components: Classification
Affects Versions: 0.5
Reporter: Stanley Xu
I am trying to use the MixedGradient in OnlineLogisticRegression algorithm. But
I will get an NullPointerException randomly if I set the alpha larger than 0.
I checked the code and found that in the RankingGradient used by MixedGradient,
it assume that the target category should be only 2, rather than multiple. And
the rank gradient should only be used once the Gradient object knew both the
positive and negative targets. I created a simple patch to make it workable,
but I am not really understand the MixedGradient method deeply, please check
the patch carefully to see if it really works correctly.
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