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https://issues.apache.org/jira/browse/MAHOUT-1058?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sebastian Schelter updated MAHOUT-1058:
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Comment: was deleted
(was: The change is only meant to increase performance. It is true that the
items will already be filtered after the estimation phase, but this will make
the recommender do lots of unnecessary work, it does need to compute
estimations if the item will be filtered out afterwards.
I guess that this change could (for some usecases) increase the number of
requests a single box can answer by an order of magnitude.)
> IDRescorers should also be able to filter candidate items
> ---------------------------------------------------------
>
> Key: MAHOUT-1058
> URL: https://issues.apache.org/jira/browse/MAHOUT-1058
> Project: Mahout
> Issue Type: New Feature
> Components: Collaborative Filtering
> Affects Versions: 0.8
> Reporter: Sebastian Schelter
> Assignee: Sebastian Schelter
> Attachments: MAHOUT-1058.patch
>
>
> Currently when a recommendation for a particular user is computed, at first
> the candidate items are determined via a CandidateItemsStrategy, then
> predicitions for all these items are computed and afterwards the IDRescorer
> can filter the items that might be recommended.
> For performance reasons, it should also be possible to apply custom filtering
> before the estimation is done. This cannot be done in the
> CandidateItemsStrategy, as the filtering logic might depend on some
> request/or user-specific criteria that are not known in the recommender
> application.
> It would be possible to implement such a logic in IDRescorer.isFiltered(),
> this is however bad for performance reasons, as the very costly estimation
> has already happen then.
> I propose to add a method to IDRescorer that can filter the candidate items
> right before estimation starts.
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