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https://issues.apache.org/jira/browse/MAHOUT-1428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13989284#comment-13989284
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Sebastian Schelter commented on MAHOUT-1428:
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Dodi,
I had a first look at your patch. There is one big issue with it: you modify
the signature of recommend to add a parameter. Please add a new recommend
method with the parameter instead, keep the old method around and make a
default implementation that delegates to the new method with a default value of
false for your new parameter. At the moment, you break all existing code that
uses the Recommender interface, that's also why you have to edit some many
files.
Furthermore, please rename the new parameter to 'includeKnownItems', I think
that is easier to understand than 'isUserItemInclude'.
> Recommending already consumed items
> -----------------------------------
>
> Key: MAHOUT-1428
> URL: https://issues.apache.org/jira/browse/MAHOUT-1428
> Project: Mahout
> Issue Type: Bug
> Components: Collaborative Filtering
> Affects Versions: 1.0
> Reporter: Mario Levitin
> Labels: easyfix
> Fix For: 1.0
>
> Attachments: MAHOUT-1428.patch
>
>
> Mahout does not recommend items which are already consumed by the user.
> For example,
> In the getAllOtherItems method of GenericUserBasedRecommender class there is
> the following line
> possibleItemIDs.removeAll(dataModel.getItemIDsFromUser(theUserID));
> which removes user's items from the possibleItemIDs to prevent these items
> from being recommended to the user. This is ok for many recommendation cases
> but for many other cases it is not.
> The Recommender classes (I mean all of them, NN-based and SVD-based as well
> as hadoop and non-hadoop versions) might have a parameter for this for
> excluding or not excluding user items in the returned recommendations.
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