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https://issues.apache.org/jira/browse/MAHOUT-340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12849679#action_12849679
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Sean Owen commented on MAHOUT-340:
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That is a good question -- the two implement the same algorithm, but
'cooccurrence' tries to distribute the matrix - user vector multiplication,
while 'item' does not. It's not yet clear what's better. You could adapt either
one's approach to completing this multiplication.
The 'item' handles long IDs as inputs. To do this, you need to create a long
<-> int mapping between the original long IDs, and the dimensions in the vector
or matrix they map to -- which must be ints. It collects this information and
reverses the transformation later. For this reason, if you need long IDs, you
may find it more natural to adapt 'item' since it handles this issue.
> org.apache.mahout.cf.taste.hadoop.cooccurence can not support long as user_id
> and item_id
> -----------------------------------------------------------------------------------------
>
> Key: MAHOUT-340
> URL: https://issues.apache.org/jira/browse/MAHOUT-340
> Project: Mahout
> Issue Type: Improvement
> Components: Collaborative Filtering
> Affects Versions: 0.3
> Reporter: Hui Wen Han
> Fix For: 0.4
>
>
> I have preferences data using long as user_id and item_id,
> hadoop cooccurence arithmetic can not support it
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