My guess is that some defaults changed somewhere... but I can't think of anything relevant to these implementations. Alejandro do you have the ability to run a quick profiling of both, and point out where the new bottleneck is? then we would have better ideas. Also I suggest you use the latest code in Subversion.
On Thu, Dec 15, 2011 at 9:58 AM, Alejandro Bellogin Kouki < [email protected]> wrote: > Thanks Sebastian. > > This is the code I used for Mahout-0.3 and Mahout-0.5: > > int N = 1000; > long totalTime = 0L; > int n = 0; > Recommender rec = null; > final DataModel train = new FileDataModel(new File(trainFile)); > ItemSimilarity sim = new PearsonCorrelationSimilarity(**train); > sim = new CachingItemSimilarity(sim, train); > rec = new GenericItemBasedRecommender(**train, sim); > > LongPrimitiveIterator users = train.getUserIDs(); > while (users.hasNext()) { > long u = users.nextLong(); > n++; > long time = System.currentTimeMillis(); > rec.recommend(u, N); > time = System.currentTimeMillis() - time; > totalTime += time; > } > System.out.println("Average time - using cache " + strategy + " > (ms): " + (1.0 * totalTime / n)); > > In Mahout-0.3, the average time per user was 310.99 ms, and for 0.5 it was > 649.55 ms. > > As I said in my previous mail, here I was only concerned on measuring the > time performance of recommenders. > > Thanks, > Alejandro > > Sebastian Schelter escribió: > > Hi Alejandro, >> >> you have to provide a detailed description of your benchmark. >> >> There is no such thing is "the efficiency" of a recommender. Mahout >> offers a wide variety of implementations and components that can be >> glued together to form a recommender. There are a lot of knobs to adjust >> that offer trade-offs between execution time, scalability, quality and >> recency. >> >> --sebastian >> >> >> On 15.12.2011 09:30, Alejandro Bellogin Kouki wrote: >> >> >>> Hi all, >>> >>> some months ago I performed some efficiency comparisons between the >>> execution times of one implementation of mine and user- and item-based >>> CF recommenders in Mahout. By that time, I was using Mahout-0.3 and I >>> obtained some decent values, taking into account that I was measuring >>> the average recommendation time per user (that is, how long it took to >>> execute the method 'recommend(u, N)'). >>> >>> Yesterday, I decided to make the same tests with the latest stable >>> version (Mahout-0.5), and, to my suprise, the execution times in the >>> latest implementation have been multiplied by a factor of 2. >>> >>> Do you have any idea of why is that happening? Is it documented >>> anywhere? I have specific numbers and code in case you want to check >>> them out. >>> >>> I want to emphasize that I am measuring how much time the recommender >>> spends on generating a ranking, and, probably, if you have changed how >>> the plausible items to be recommended for a user are obtained, then this >>> change may have caused this situation. >>> >>> Thank you in advance. >>> >>> Best regards, >>> Alejandro >>> >>> >>> >> >> >> >> > > -- > Alejandro Bellogin Kouki > > http://rincon.uam.es/dir?cw=**435275268554687<http://rincon.uam.es/dir?cw=435275268554687> > >
