[jira] [Updated] (MAHOUT-905) CachingUserSimilarity and CachingItemSimilarity have wrong (far to small) default maxSizes

["Manuel Blechschmidt (Updated) (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAHOUT-905?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Manuel Blechschmidt updated MAHOUT-905:
---------------------------------------

    Attachment: CachingSimilariyAdjustedDefaultSize.patch

The attached patch fixes this issue.
                
> CachingUserSimilarity and CachingItemSimilarity have wrong (far to small) default maxSizes
> ------------------------------------------------------------------------------------------
>
>                 Key: MAHOUT-905
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-905
>             Project: Mahout
>          Issue Type: Bug
>          Components: Collaborative Filtering
>    Affects Versions: 0.5
>         Environment: Mac OS X 10.6.8
> java version "1.6.0_29"
> Java(TM) SE Runtime Environment (build 1.6.0_29-b11-402-10M3527)
> Java HotSpot(TM) 64-Bit Server VM (build 20.4-b02-402, mixed mode)
> This does not matter should be reproducible on every system.
>            Reporter: Manuel Blechschmidt
>            Assignee: Sean Owen
>              Labels: caching, max, similarity
>         Attachments: CachingSimilariyAdjustedDefaultSize.patch
>
>   Original Estimate: 0.5h
>  Remaining Estimate: 0.5h
>
> I am currently tuning my recommender discussed here: http://thread.gmane.org/gmane.comp.apache.mahout.user/10433.
> As a first step I wrapped my LogLikelihoodSimilarity with an CachingUserSimilarity. I used Java Visual VM to profile the calls. I recognized that I didn't get any performance benefits. So I had a look into the code.
> Actually line 47 this(similarity, dataModel.getNumItems()); in CachingUserSimilarity.java is wrong. If we want to cache all item similarities we need a cache with (dataModel.getNumItems()*(dataModel.getNumItems()-1))/2 possible entries.
> I am now doing this in the constructor. I attached a patch to adjust this in the trunk build.

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