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  1. Mahout
  2. MAHOUT-905

CachingUserSimilarity and CachingItemSimilarity have wrong (far to small) default maxSizes

    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Minor
    • Resolution: Not A Problem
    • Affects Version/s: 0.5
    • Fix Version/s: None
    • Environment:

      Description

      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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            • Assignee:
              srowen Sean Owen
              Reporter:
              manuel_b Manuel Blechschmidt
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