I have read some code about item-based recommendation in version-0.6, starting from "org.apache.mahout.cf.taste. hadoop.item.RecommenderJob". I found that there is a Long-to-Int mapping provided by the function "int TasteHadoopUtils.idToIndex(long)". Long-to-Int is performed both on userId and itemId. I wonder if it possible to have two long mapped into one int? If it is the case, then we would likely to merge vectors from different itemids/uids, right? This is quite confusing.
Is it better to provide a RandomAccessSparseVector implemented by OpenLongDoubleHashMap instead of OpenIntDoubleHashMap? Thanks in advance. ---------------------- Wei Feng
