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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: Computing userSimilarity in Taste AbstractSimilarity
Date Fri, 01 Oct 2010 01:38:14 GMT
Also, it is best to get the source from apache or a mirror.

See

SVN URL: http://svn.apache.org/repos/asf/mahout/trunk
Apache git mirror of same: git://git.apache.org/mahout.git
Github mirror of mahout: http://github.com/apache/mahout


On Thu, Sep 30, 2010 at 2:53 PM, Abigail Gertner <gertner@mitre.org> wrote:

>  I think I must be looking at an older version of the file. I have
> mahout-0.3 (the most recent one) downloaded from sourceforge. Maybe it
> is updated since then in SVN?
>
>
> On 9/30/2010 5:38 PM, Sean Owen wrote:
> > I think it does work, but this code is definitely hard to grok. In my
> > defense it is complex for a reason at least -- performance.
> >
> > When the end of one list of prefs is reached (the line "if (++xPrefIndex
> >=
> > xLength)") it does check for an inferrer in the next line. If there is
> one,
> > it sets "xIndex = Long.MAX_VALUE", and continues. This ensures the rest
> of
> > the y values are compared against an inferred x value.
> >
> > Step through to convince yourself. Or, if you find I am actually
> completely
> > wrong do let me know.
> >
> > On Thu, Sep 30, 2010 at 10:20 PM, Abigail Gertner <gertner@mitre.org>
> wrote:
> >
> >> Hello - I noticed something that I think might be a problem with the
> >> userSimilarity computation in the AbstractSimilarity class. After
> >> updating the running sums, the method checks the value of compare and
> >> moves to the next preference value in the list that has the smaller item
> >> index, or both if they are both on the same item. It breaks out of the
> >> loop if it is at the end of the preference list(s) that it needs to get
> >> the next value of. The problem is that it doesn't take into account if
> >> there is a preference inferrer -- if it is at the end of one of the
> >> lists, it will break out of the loop even if there is a preference
> >> inferrer. This results in ignoring the rest of the items in the other
> >> users preferences.
> >>
> >> Am I missing something or does this need to be corrected?
> >>
> >> Thanks for your help,
> >> -Abigail
> >>
> >>
>

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