title: Vowpal Wabbit predictions for multi-label classification
body: <p>I am sorry, I do feel I am overlooking something really obvious.</p>
  
  <p>But how can the following happen:</p>
  
  <pre><code>$ cat myTrainFile.txt
  1:1 |f 1:12 2:13
  2:1 |f 3:23 4:234
  3:1 |f 5:12 6:34
  
  $ cat myTestFile.txt 
  14:1 |f 1:12 2:13
  14:1 |f 3:23 4:234
  14:1 |f 5:12 6:34
  
  $ vw --csoaa 3 -f myModel.model --compressed &lt; myTrainFile.txt 
  final_regressor = myModel.model
  ...
  ...
  
  $ vw -t -i myModel.model -p myPred.pred &lt; myTestFile.txt 
  only testing
  Num weight bits = 18
  ...
  ...
  
  $ cat myPred.pred 
  14.000000
  14.000000
  14.000000
  </code></pre>
  
  <p>So the test file is identical to the train file, but for the labels.
  Hence, I would expect vw to produce the original labels that it learned from the train file, as it ignores the labels in the test file completely.</p>
  
  <p>However, it seems to reproduce the labels form the test file?!?</p>
  
  <p>Clearly, I am doing something completely wrong here... but what?</p>