[MAHOUT-1958] CityBlockSimilarity.itemSimilarities can overflow

• Type: Bug
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.0.0
• Fix Version/s: classic-15.0
• Component/s: classic
• Assignee: Shashanka Balakuntala Srinivasa
• Reporter: Hao Zhong
• Created: 21/Mar/17 08:24
• Updated: 31/Jan/24 22:16

Description

The CityBlockSimilarity.itemSimilarities method has the following code:

CityBlockSimilarity.java

      int preferring2 = dataModel.getNumUsersWithPreferenceFor(itemID2s[i]);
      int intersection = dataModel.getNumUsersWithPreferenceFor(itemID1, itemID2s[i]);

Here, the two methods return long values, and can overflow. Indeed, LogLikelihoodSimilaritydoItemSimilarity once had the same problem. The fixed code is

LogLikelihoodSimilaritydoItemSimilarity.java

    long preferring1 = dataModel.getNumUsersWithPreferenceFor(itemID1);
    long numUsers = dataModel.getNumUsers();

Please refer to MAHOUT-738 for details.