[GitHub] [madlib] njayaram2 commented on a change in pull request #361: Minibatch Preprocessor DL: Add optional num_classes param.

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njayaram2 commented on a change in pull request #361: Minibatch Preprocessor DL: Add optional num_classes param.
URL: https://github.com/apache/madlib/pull/361#discussion_r271494568
 
 

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 File path: src/ports/postgres/modules/utilities/minibatch_preprocessing.py_in
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 @@ -363,21 +365,70 @@ class MiniBatchPreProcessorDL(MiniBatchPreProcessor):
 
         self._validate_args()
         self.num_of_buffers = self._get_num_buffers()
-        self.to_one_hot_encode = True
 
 Review comment:
   Our 1-hot encoding follows the standard one-hot encoding convention. In fact, it is different from `keras.to_categorical`. For example, if there are 3 distinct class values captured in a list `y=[10, 11, 12]`, then the 1-hot encoded vector created by`keras.to_categorical(y)` is of size 13 (largest class value + 1). If it is called with `keras.to_categorical(y, num_classes=4)`, it errors out.
   The 1-hot encoding done in MADlib would create a 1-hot encoded vector of size 4 in both cases.
   
   I would say keras' 1-hot encoding is actually not the standard way of doing it.

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