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From "Maciej Grzenda (JIRA)" <>
Subject [jira] [Created] (SAMOA-73) Exception in VHT method terminates stream processing
Date Fri, 29 Sep 2017 14:37:02 GMT
Maciej Grzenda created SAMOA-73:

             Summary: Exception in VHT method terminates stream processing
                 Key: SAMOA-73
             Project: SAMOA
          Issue Type: Bug
          Components: SAMOA-API
            Reporter: Maciej Grzenda
            Priority: Minor
         Attachments: vht_error_stderr.txt

VHT method when executed on some data streams throws java.lang.NullPointerException. This
happens after processing some instances, which seems to be related to problems with creating
a split.  The problem can be observed on airlines.arff from MOA.

Sample command to replicate the problem:
java -cp target/SAMOA-Local-0.5.0-incubating-SNAPSHOT.jar org.apache.samoa.LocalDoTask "org.apache.samoa.tasks.PrequentialEvaluation
-l org.apache.samoa.learners.classifiers.trees.VerticalHoeffdingTree -s (ArffFileStream -f
airlines.arff) -f 10" 

Under such settings ca. 400 instances are processed correctly. The last output of evaluator
classified instances = 390
classifications correct (percent) = 77,436
Kappa Statistic (percent) = 13,07
Kappa Temporal Statistic (percent) = 29,6

Next the exception is thrown, which terminates the processing (see attached stack trace)

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