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https://issues.apache.org/jira/browse/MAHOUT-593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12994470#comment-12994470
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Ted Dunning commented on MAHOUT-593:
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{quote}
Sorry, not to start a discussion on this or anything, but just for my
information, is this is project-wide consensus or it is your opinion? I don't
think i am with you on this, nor do i think i see consensus in the project. I
did not scan all the Mahout tree for this but just scanning one package up, all
the DRM jobs seem to be happily use inner classes. At least it seems there
wasn't such consensus until pretty recently. Hadoop literature that i scanned
seems to use inner classes too.
{quote}
I typically prefer inner classes for mappers and reducers as long as they are
static. I have no problem finding them since IntelliJ hunts them down
instantly. It is a bit of a pain from vi. From emails etags will find inner
classes as easily as anything.
> Backport of Stochastic SVD patch (Mahout-376) to hadoop 0.20 to ensure
> compatibility with current Mahout dependencies.
> ----------------------------------------------------------------------------------------------------------------------
>
> Key: MAHOUT-593
> URL: https://issues.apache.org/jira/browse/MAHOUT-593
> Project: Mahout
> Issue Type: New Feature
> Components: Math
> Affects Versions: 0.4
> Reporter: Dmitriy Lyubimov
> Fix For: 0.5
>
> Attachments: MAHOUT-593.patch.gz
>
>
> Current Mahout-376 patch requries 'new' hadoop API. Certain elements of that
> API (namely, multiple outputs) are not available in standard hadoop 0.20.2
> release. As such, that may work only with either CDH or 0.21 distributions.
> In order to bring it into sync with current Mahout dependencies, a backport
> of the patch to 'old' API is needed.
> Also, some work is needed to resolve math dependencies. Existing patch relies
> on apache commons-math 2.1 for eigen decomposition of small matrices. This
> dependency is not currently set up in the mahout core. So, certain snippets
> of code are either required to go to mahout-math or use Colt eigen
> decompositon (last time i tried, my results were mixed with that one. It
> seems to produce results inconsistent with those from mahout-math
> eigensolver, at the very least, it doesn't produce singular values in sorted
> order).
> So this patch is mainly moing some Mahout-376 code around.
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