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From Nick Jordan <>
Subject Re: Decision Forest/Partial Implementation TestForest Error
Date Thu, 06 Sep 2012 11:00:36 GMT
Same problem with the sequential classifier.  My guess is that this
"corruption" is happening because of that particular setting as it is
the only thing that I'm changing, but I have no idea how to
investigate further.


On Thu, Sep 6, 2012 at 2:22 AM, Abdelhakim Deneche <> wrote:
> Hi Nick,
> This is not a memory problem, the classifier tries to load the trained forest but it's
getting some unexpected values. This problem never occured before! Could the forest files
be corrupted ?
> Try training the forest once again, and this time use the sequential classifier (don't
use the -mr parameter) and see if the problem still occurs.
> On 5 sept. 2012, at 23:00, Nick Jordan <> wrote:
>> Hello All,
>> I'm playing around with decision forests using the partial
>> implementation and my own data set.  I am getting an error with
>> TestForest, but only for certain forests that I'm building with
>> BuildForest.  Using the same descriptor and same build and test data
>> sets I get no error if I set mapred.max.split.size=1890528 which is
>> roughly 1/100th the size of the build data set.  I can build the
>> forest and test the remaining data and get the results with no
>> problem.  When I change the split size to 18905280, everything still
>> appears to work fine when building the forest, but when I then try to
>> test the remaining data I get the error below.
>> I've dug around the code a little, but nothing stood out as to why the
>> array would go out of bounds at that specific value.  One solution is
>> to obviously not create partitions that large, but if it was a problem
>> with me running out of memory I would have expected an out of memory
>> error and not an index past the size the bounds of an array.  I'd
>> obviously prefer larger partitions and thus less of them and can move
>> running this job to something like EMR which should allow me to have
>> more memory, but I want to understand the nature of the error.
>> For what it is worth I'm running this on hadoop-1.0.3 and mahout-0.8-SNAPSHOT
>> Thanks.
>> --
>> 12/09/05 17:52:09 INFO mapred.JobClient: Task Id :
>> attempt_201209031756_0008_m_000000_0, Status : FAILED
>> java.lang.ArrayIndexOutOfBoundsException: 946827879
>>        at
>>        at org.apache.mahout.classifier.df.DecisionForest.readFields(
>>        at
>>        at org.apache.mahout.classifier.df.DecisionForest.load(
>>        at org.apache.mahout.classifier.df.mapreduce.Classifier$CMapper.setup(
>>        at
>>        at org.apache.hadoop.mapred.MapTask.runNewMapper(
>>        at
>>        at org.apache.hadoop.mapred.Child$
>>        at Method)
>>        at
>>        at
>>        at org.apache.hadoop.mapred.Child.main(

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