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From Sean Owen <>
Subject Re: problems evaluating item based recommender
Date Wed, 02 Sep 2009 09:21:28 GMT
Claudia I believe I've replied to you several times on this mailing
list with possible reasons you are observing this behavior. I am not
clear that you followed up on them, so would point you back to those

You're using a port, of an old version of the code, and we don't have
access to your data, or your code, and you are unable to debug. I am
not sure it is really possible to offer more support then. I strongly
suggest you learn how to run a debugger; it will be extremely useful
here and should point out the cause immediately. It is definitely
possible to debug C#.

It might be useful to compare the port to the current version of these
classes in Java to see if any meaningful changes have occurred that
you might want to re-port.

Mahout 0.2 is probably coming in a month or so. I think this part of
the code is reasonably stable. I don't have any changes planned, and
it's had some time to work out bugs. But I would first encourage you
to get a debugger going rather than update. I don't think it will
'fix' this problem, I think it's a function of your data.

2009/9/2 Claudia Grieco <>:
> I'm using an old version of mahout (before the big branch of mahout-150) and
> the evaluation of my item based recommender done with
> GenericRecommenderIRStatsEvaluator doesn't work very well: it always returns
> precision 0 and recall 0. I'm using a port of mahout in C# so I can't debug
> it properly, but I've seen that the program seems to recommend almost the
> same items to everyone and in numerical order (es. 612,613,614.).
> What do you think could be the problem?
> (anyway, how much do you think it would take to adjust a program to pass
> from the old version of mahout to the new one? Is there going to be a stable
> new release in the near future?)

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