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https://issues.apache.org/jira/browse/MAHOUT-593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13001215#comment-13001215
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Dmitriy Lyubimov edited comment on MAHOUT-593 at 3/2/11 12:50 AM:
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It's just housekeeping of the resources. It's not so much the case here, but in
other situations you might have a resource tree open. e.g. you may have
something representing a filesystem (on top), and bunch of files underneath it,
plus might potentially have compressors attached to files etc.
if you decide to collapse (commit) that system then you need to flush (close)
compressors first, then close the files, and then potentially close a
filesystem. Along those lines. Hence the order.
Reference release has to do with the fact that you might have flushed some or
all of the resources and closed them, so you want to release reference from
collection as well in order for GC to collect it. This helper does it
automatically.
Finally, you do want to receive "noise" to promote it up when you commit the
resource tree if one of the resources failed to commit (close). The only
exception when you probably don't care about noise if that's an error path
already.
Again, i see it is probably not so much the case in this case, but it is often
the case.
was (Author: dlyubimov2):
It's just housekeeping of the resources. It's not so much the case here,
but in other situations you might have a resource tree open. e.g. you may have
something representing a filesystem (on top), and bunch of files underneath it,
plus might potentially have compressors attached to files etc.
if you decide to collapse that system that you need to flush (close)
compressors first, then close the files, and then potentially close a
filesystem. Along those lines. Hence the order.
Reference release has to do with the fact that you might have flushed some or
all of the resources and closed them, so you want to release reference from
collection as well in order for GC to collect it. This helper does it
automatically.
Finally, you do want to receive "noise" to promote it up when you commit the
resource tree if one of the resources failed to commit (close).
Again, i see it is probably not so much the case in this case, but it is often
the case.
> 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, MAHOUT-593.patch.gz,
> MAHOUT-593.patch.gz, SSVD-givens-CLI.pdf, ssvdclassdiag.png
>
>
> 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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