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https://issues.apache.org/jira/browse/MAHOUT-1106?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13498767#comment-13498767
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Sean Owen commented on MAHOUT-1106:
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Yes I think this is true -- ignoring lambda. The SVD++ model is explaining the
user's latent factors as some combination of explicit and implicit factors. Why
does the model think you like Shrek? Is it because you rated Shrek 4 stars or
clicked it 6 times? Either, both or some of both could make sense. The
regularization parameter does constrain it to a 'simple' explanation involving
the two and lambda should be positive. So if the premise is no regularization
-- don't do that, I suppose. You don't necessarily have a unique solution even
with regularization but it is not of this form.
There's a more interesting general question about explicit vs implicit
feedback. I certainly don't think you can ignore implicit feedback. Most of the
data in the world is implicit. My question is really whether it's more
interesting to forget 'explicit' data entirely since it's rare and noisy. This
is why I personally like ALS-WR, as it is really just the same thing, much
simplified and faster since there is no mean or explicit term to worry about.
You could argue it's coarser, but if you believe it's a world of 99% implicit
data, it is negligibly different.
> SVD++
> -----
>
> Key: MAHOUT-1106
> URL: https://issues.apache.org/jira/browse/MAHOUT-1106
> Project: Mahout
> Issue Type: New Feature
> Components: Collaborative Filtering
> Reporter: Zeno Gantner
> Assignee: Sebastian Schelter
> Attachments: SVDPlusPlusFactorizer.java
>
>
> Initial shot at SVD++.
> Relies on the RatingsSGDFactorizer class introduced in MAHOUT-1089.
> One could also think about several enhancements, e.g. having separate
> regularization constants for user and item factors.
> I am also the author of the SVDPlusPlus class in MyMediaLite, so if there are
> any similarities, no need to worry -- I am okay with relicensing this to the
> Apache 2.0 license.
> https://github.com/zenogantner/MyMediaLite/blob/master/src/MyMediaLite/RatingPrediction/SVDPlusPlus.cs
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