[
https://issues.apache.org/jira/browse/MAHOUT-322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12841382#action_12841382
]
Jake Mannix commented on MAHOUT-322:
------------------------------------
Meaning what, Robin?
We can certainly come up with lots of ways to start with a
SequenceFile<Writable,VectorWritable> and end up with a
SequenceFile<IntWritable,VectorWritable> (I've currently do it by simply
iterating over the sequence file assigning increasing integers - it's not
scalable, but it's plenty fast enough for most purposes, and you only have to
do it once per matrix - you store the output IntWritable,VectorWritable matrix
and IntWritable,Writable dictionary files separately and they can be reused).
> DistributedRowMatrix should live in SequenceFile<Writable,VectorWritable>
> instead of SequenceFile<IntWritable,VectorWritable>
> -----------------------------------------------------------------------------------------------------------------------------
>
> Key: MAHOUT-322
> URL: https://issues.apache.org/jira/browse/MAHOUT-322
> Project: Mahout
> Issue Type: Improvement
> Components: Math
> Affects Versions: 0.3
> Reporter: Danny Leshem
> Priority: Minor
> Fix For: 0.3
>
>
> Class documentation for org.apache.mahout.math.hadoop.DistributedRowMatrix
> states that the matrix lives in SequenceFile<WritableComparable,
> VectorWritable>. Implementation, however, assumes SequenceFile<IntWritable,
> VectorWritable> is passed.
> Currently, usage of this class inside Mahout is limited to Jake Mannix's SVD
> package, mainly to perform PCA on a massive document corpus. Given such
> corpus, it makes sense to not limit the user by forcing the document "key" to
> be integer. Instead, users should be able to use Text keys (document name or
> id) or keys made of any other arbitrary class. One may even argue that
> forcing a WritableComparable key is too limiting, and a simple Writable key
> should be assumed.
> In fact, it would be best if DistributedRowMatrix did not read the
> SequenceFile key at all, to allow user-specific classes (unknown to Mahout)
> to be used as opaque keys even when their libraries are not available in
> runtime. Currently DistributedRowMatrix calls "reader.next(i, v)"... but
> reader has methods to query just the value, avoiding key deserialization
> altogether.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
