Thanks guys for the help Claudia -----Messaggio originale----- Da: Manuel Blechschmidt [mailto:[email protected]] Inviato: giovedì 8 marzo 2012 16.15 A: [email protected] Oggetto: Re: R: R: Using recommenders with String identifiers
Hi Claudia, actually a kind of. With the IDMigrator it depends how you store them. You can store them in memory, in a database or in a file. Further if you would use strings these strings would get copied multiple times and therefore would use multiple times the amount of there memory. So you could supply a recommender implementation which is doing the String Long mapping transparently for the user and put in on github. Currently there is a lack of easy to understand examples. I tried to help a little bit with my facebook-recommender-demo. /Manuel On 08.03.2012, at 15:52, Claudia Grieco wrote: > I understand, but with IDMigrator I still need the memory to store the > long-string mappings, isn't it? > > -----Messaggio originale----- > Da: Sebastian Schelter [mailto:[email protected]] > Inviato: giovedì 8 marzo 2012 15.27 > A: [email protected] > Oggetto: Re: R: Using recommenders with String identifiers > > Here's some details on the memory usage of Strings in Java: > > http://www.javamex.com/tutorials/memory/string_memory_usage.shtml > > On 08.03.2012 14:53, Manuel Blechschmidt wrote: >> Hallo Claudia, >> the reason why longs are use is pure efficiency. When you have a lot of > things and a lot of users and you are using Strings as identifiers you will > need a lot of memory just for saving them. Further processes like equals or > hash codes will take longer. >> >> So a long has 4 bytes (64 bits) a UUID string (e.g. > 936DA01F-9ABD-4D9D-80C7-02AF85C822A8) encoded as utf-16 has 72 bytes that > means that UUID would consume more then18x the memory that longs are taking. >> >> /Manuel >> >> >> On 08.03.2012, at 14:27, Claudia Grieco wrote: >> >>> Do you think it's worth the work to change the internal code of Mahout in >>> order to use string identifiers? >>> Thanks >>> Claudia >>> >>> -----Messaggio originale----- >>> Da: Manuel Blechschmidt [mailto:[email protected]] >>> Inviato: lunedì 5 marzo 2012 11.28 >>> A: [email protected] >>> Oggetto: Re: Using recommenders with String identifiers >>> >>> Hi Claudia, >>> you have to use an IDMigrator. >>> >>> The following projects shows you an example: >>> https://github.com/ManuelB/facebook-recommender-demo >>> >>> > https://github.com/ManuelB/facebook-recommender-demo/blob/master/src/main/ja >>> va/de/apaxo/bedcon/FacebookRecommender.java >>> >>> Good luck >>> Manuel >>> >>> On 05.03.2012, at 09:53, Claudia Grieco wrote: >>> >>>> Hi guys, >>>> >>>> I'd like to use mahout to implement a recommender but I'm encountering a >>>> problem: >>>> >>>> Ids of items and users are represented in Mahout as long integers, while >>> my >>>> data comes from an external database that uses strings to identify items >>> and >>>> users. >>>> >>>> Any suggestion as to how I can fix this problem? >>>> >>>> Thanks a lot >>>> >>>> Claudia >>>> >>> >>> -- >>> Manuel Blechschmidt >>> Dortustr. 57 >>> 14467 Potsdam >>> Mobil: 0173/6322621 >>> Twitter: http://twitter.com/Manuel_B >>> >>> >> > -- Manuel Blechschmidt Dortustr. 57 14467 Potsdam Mobil: 0173/6322621 Twitter: http://twitter.com/Manuel_B
