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https://issues.apache.org/jira/browse/MAHOUT-162?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12746724#action_12746724
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Ted Dunning commented on MAHOUT-162:
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Mahout uses java 1.6 where there is an advantage to do so. This requirement is
inherited from Hadoop.
This code that you mention is a good example of an additional small improvement
available with 1.6. The java 5 version of getBytes throws an
UnsupportedEncodingException which is a checked exception. Since there isn't
much that you can do about this, that is just pain for no gain.
> Added support for mapping String to long IDs in CF code
> -------------------------------------------------------
>
> Key: MAHOUT-162
> URL: https://issues.apache.org/jira/browse/MAHOUT-162
> Project: Mahout
> Issue Type: Improvement
> Components: Collaborative Filtering
> Affects Versions: 0.2
> Reporter: Sean Owen
> Assignee: Sean Owen
> Fix For: 0.2
>
> Attachments: MAHOUT-162.patch
>
>
> Since the framework now only allows long (64-bit integer) IDs, and no longer
> Strings, we need to provide some support for translating between the two. The
> basic proposal is this:
> - Define a one-way mapping from Strings to longs that is repeatable and easy
> to implement in many contexts. In particular I propose using the bottom 64
> bits of the MD5 hash of a string.
> - Define support for storing the reverse mapping (longs to Strings) in
> various ways, in an efficient way, that handles gracefully the very rare
> possibility of collision
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