[jira] Created: (MAHOUT-407) Limit the number of similar items per item in the ItemSimilarityJob

["Sebastian Schelter (JIRA)" <ji...@apache.org>]

Limit the number of similar items per item in the ItemSimilarityJob
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                 Key: MAHOUT-407
                 URL: https://issues.apache.org/jira/browse/MAHOUT-407
             Project: Mahout
          Issue Type: New Feature
          Components: Collaborative Filtering
            Reporter: Sebastian Schelter


In order to keep the item-similarity-matrix sparse, it would be a useful improvement to add an option like "maxSimilaritiesPerItem" to o.a.m.cf.taste.hadoop.similarity.item.ItemSimilarityJob, which would make it try to cap the number of similar items per item.

However as we store each similarity pair only once it could happen that there are more than "maxSimilaritiesPerItem" similar items for a single item as we can't drop some of the pairs because the other item in the pair might have too little similarities otherwise.

A default value of 100 co-occurrences (similarities) will be used because this is already the default in the distributed recommender.

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