[
https://issues.apache.org/jira/browse/MAHOUT-195?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Sean Owen resolved MAHOUT-195.
------------------------------
Resolution: Fixed
Fix Version/s: 0.3
Assignee: Sean Owen
OK committed my javadoc change, and getDiff() improvement. TYVM
> doubt about SlopeOneRecommender
> -------------------------------
>
> Key: MAHOUT-195
> URL: https://issues.apache.org/jira/browse/MAHOUT-195
> Project: Mahout
> Issue Type: Question
> Components: Collaborative Filtering
> Reporter: Jens Grivolla
> Assignee: Sean Owen
> Priority: Minor
> Fix For: 0.3
>
>
> Looking through the SlopeOne code in order to make some changes, I am having
> some doubts about how MemoryDiffStorage handles things.
> It looks to me like buildAverageDiffs(), or rather processOneUser() inserts
> the item pairs in the order they appear in userPreferences, as obtained from
> dataModel.getPreferencesFromUser(userID).
> So if user A has items (X,Y,Z) we obtain the pairs (X,Y),(X,Z),(Y,Z) and
> update their averages,
> if user B has items (Z,X,Y) we obtain (Z,X),(Z,Y),(X,Y).
> When using getDiff for (Y,Z) it will not look for the (Z,Y) average that user
> B contributes to, as the average for (Y,Z) is not null.
> Unless we know that preferences are always ordered, e.g. by itemID, this
> seems like a bug. I have not found any mention of it being ordered in the
> documentation of DataModel or PreferenceArray. If the items are ordered it
> would seem to be easier to check the order in getDiff(x,y) instead of trying
> one, then the other.
> P.s.: I tried to ask on mahout-users, but my message never appeared on the
> list. There might be some kind of filter rejecting the plus sign in my
> address or something like that, but it's the one where I receive the list
> messages.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
