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From Doron Cohen <DOR...@il.ibm.com>
Subject Re: The values which compute scores. - Part II
Date Fri, 01 Jun 2007 22:40:41 GMT
Hi Walt,

AFAIK there is no flag guiding scorers to "ignore norms".
I guess you could hack a "all norms are 1" behavior by
writing something similar to OneNormsReader in
org.apache.lucene.demo.SearchFiles.

Doron

Walt Stoneburner wrote on 01/06/2007 13:45:26:

> I've managed to build my own Similarity class, plug it in, and use
> Explain to convince myself that I am, indeed, getting the correct
> weightings that I desire.  My test case documents are yielding
> precisely the intermediate values needed for alternate scoring.
>
> There's just one thing...
>
> When I do an .explain(), I'm getting values back for the fieldNorm()
> that are improperly biasing my scores.
>
> According to http://www.mail-archive.com/lucene-user@jakarta.
> apache.org/msg06275.html,
> this value is actually computed at index time.
>
> Indeed, that is the case, for if I generate a new index using my
> custom Similarity class, the bias disappears and all is right with the
> world.
>
> However, I'm not exactly thrilled at the prospect of maintaining a
> second index.  Recall from the initial message that users will be
> toggling between the standard scoring and the alternative.
>
> And while, yes, I know that this value is precomputed and stored in
> the index, what I'd like to be able to do is simply ignore it.
>
> Somewhere the code that computes that big huge scoring equation has to
> pull that value and use it.  I figure if I override -that-, I can
> simply ignore the value and treat fieldNorm() as 1 when the custom
> version is used.
>
> Only problem is, I'm not sure if this is a property set somewhere, a
> method override in a replacement class, or some more brain surgery on
> my one-off version of Lucene.


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