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January 30, 2008 • By Mike Grafton • Standup
Does anybody know anything about Lucene scoring using a document boost?
We see an exponential relationship between document boost and the fieldNorm component of the score for each term. Can anybody explain this?
Ask someone on the Lucene mailing list, or maybe on the Acts As Solr mailing list (if you’re acts_as_solr)
Not sure what you mean by exponential. Some examples would help.
If you need help, either consult Lucene ML or http://sematext.com/
I’ll give an example below, but for the record we solved this by upgrading our version of Lucene (we’re now using 2.1, which is what SOLR 1.2 uses).
Here’s a little table the shows the relationship we saw between the document boost and the ‘fieldNorm’ component of the score contributed by one of the query terms that hit:
1.0 0.3125 = (5/16, 2^-1.678)
2.0 20.0 = (2^4.3219, 2^1 * 10)
3.0 256.0 = (2^8)
4.0 1280.0 = (2^10.3219, 2^7 * 10)
5.0 5120.0 = (2^12.3219, 2^9 * 10)
6.0 16384.0 = (2^14.0)
7.0 40960.0 = (2^15.3219, 2^12 * 10)
8.0 81920.0 = (2^16.3219, 2^13 * 10)
10.0 327680.0 = (2^18.3219, 2^15 * 10)
With the newer code we see a linear relationship.
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