Hi Young, I don't know of a good way to precompute all candidate items for a user, I don't think this makes sense as the data might become to large. But the performance of getAllOtherItems(...) depends on the implementation of DataModel you use. If all your preference data fits into memory (a single preference needs 28 bytes according to Sean AFAIK) you could think about exporting the preferences to a file and use the FileDataModel implementation that loads all data into memory.
--sebastian Am 20.07.2010 17:38, schrieb Young: > Hi again, > When I do the itembased recommendation, I find there are some latency in > getAllOtherItems(long userID). Because it is calculating the items' neighbors > and merge these neighbors together. So I am thinking if I precompute each > item's neighbors and store in the database, then when I getAllOtherItems(), I > could merge these neighbors directly. Is this useful for reducing the > latency? > Or is there other way to make the online-recommendation much faster? > Thank you. > > > > > >> Yes you probably want a new, separate table. You have an extra step of >> computing some notion of similarity anyway, and you probably want to >> separate this table from your main data table anyhow for reasons of >> performance and business logic separation. >> >> 2010/7/19 Young <[email protected]>: >> >>> So my prpblem is that I want to build datamodel based on what user has >>> bought or added to their favorite or rated. >>> You mean I need a table describe all these user behavior. For example, if >>> user buys one item, I guess the user preference is 4 and add into this >>> table? >>> >>> >>> >>> >>> >>>> No, you need one table (or view if you like) containing all data. If >>>> you can't do this, you could write your own copy of a JDBCDataModel >>>> that can query multiple tables, or, that changes its SQL queries to >>>> use UNION statements. I imagine it will slow down a lot. >>>> >>>> If you mean, can you use a table with preferences with a model that >>>> ignores preferences, sure you can. The extra column is ignored. >>>> >>>> 2010/7/19 Young <[email protected]>: >>>> >>>>> Hi, >>>>> I have three tables, one is with preference and another two are without >>>>> preference. Does mahout have some algorithm to integret these tables into >>>>> one datamodel? >>>>> >>>>> Thank you >>>>> >>>
