how is the fieldNorm factor computed from?

[leibniz <se...@gmail.com>]

i saw someone said that this fieldNor factor is consisted out of :docboost
,fieldboost and lengthNorm.
but i tried to computed like this,but the result is not the same as lucene's
output.
who can tell me in detail?thanks.
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Re: how is the fieldNorm factor computed from?

[Simon Willnauer <si...@googlemail.com>]

On Tue, Aug 11, 2009 at 10:35 AM, leibniz<se...@gmail.com> wrote:
>
> i saw someone said that this fieldNor factor is consisted out of :docboost
> ,fieldboost and lengthNorm.
> but i tried to computed like this,but the result is not the same as lucene's
> output.
The factors you use seem to be correct (see link below). I could
imagine that you use different float values than the ones used in the
scoring process. Lucene stores norm values as a 1 byte float value
this will suffer from precision lost once the values are stored. Could
that cause the differences?

> who can tell me in detail?thanks.
You find the details for computing the norm value here:
http://lucene.apache.org/java/2_4_1/api/core/org/apache/lucene/search/Similarity.html#formula_norm

simon
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