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https://issues.apache.org/jira/browse/MAHOUT-1055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13434026#comment-13434026
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Markus Paaso commented on MAHOUT-1055:
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How about using the first 32 bits of long value as index of array and the last
32 bits as index of element in array?
Then you have an array of arrays that can be meta-indexed with a long. :)
> Change id fields to use LongWritable instead of IntWritable
> -----------------------------------------------------------
>
> Key: MAHOUT-1055
> URL: https://issues.apache.org/jira/browse/MAHOUT-1055
> Project: Mahout
> Issue Type: Bug
> Components: Clustering
> Affects Versions: 0.7
> Reporter: Markus Paaso
>
> Why is IntWritable used as id field type in Mahout CVB?
> (org.apache.mahout.clustering.lda.cvb.CachingCVB0Mapper)
> Does Long have that significant impact on performance?
> Long is much more usable as id type and int causes compatibility issues like
> the one below.
> In method org.apache.mahout.utils.vectors.lucene.Driver.getSeqFileWriter()
> LongWritable is used correctly as id field type.
> I suggest that every IntWritable id should be changed to LongWritable.
> Sequencefile produced by command 'mahout lucene.vector' cannot be handled by
> command 'mahout cvb' due to this id type incompatibility issue.
> see http://mahout.markmail.org/thread/r3m6ojkpbzlxxizy
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