Markus, The calculation is correct.
Look at your output. Result = queryWeight(text:gb) * fieldWeight(text:gb in 1) Result = (idf(docFreq=6, numDocs=26) * queryNorm) * (tf(termFreq(text:gb)=2) * idf(docFreq=6, numDocs=26) * fieldNorm(field=text, doc=1)) This you should notice that idf(docFreq=6, numDocs=26 is repeated twice. This si just how the weight() is calculated. > > 0.18314168 = (MATCH) sum of: > > 0.18314168 = (MATCH) weight(text:gb in 1), product of: > > 0.35845062 = queryWeight(text:gb), product of: > > 2.3121865 = idf(docFreq=6, numDocs=26) > > 0.15502669 = queryNorm > > > > 0.5109258 = (MATCH) fieldWeight(text:gb in 1), product of: > > 1.4142135 = tf(termFreq(text:gb)=2) > > 2.3121865 = idf(docFreq=6, numDocs=26) > > 0.15625 = fieldNorm(field=text, doc=1) On 10/5/11 11:42 AM, "Markus Jelsma" <markus.jel...@openindex.io> wrote: >Hi, > >I don't see 2.3121865 * 2 anywhere in your debug output or something that >looks like that. > > >> Hi Markus, >> >> The idf calculation itself is correct. >> What I am trying to understand here is why idf value is multiplied >>twice >> in the final score calculation. Essentially, tf x idf^2 is used instead >> of tf x idf. >> I'd like to understand the rational behind that. >> >> On Wed, Oct 5, 2011 at 9:43 AM, Markus Jelsma ><markus.jel...@openindex.io>wrote: >> > In Lucene's default similarity idf = 1 + ln (numDocs / df + 1). >> > 1 + ln(26 / 7) =~ 2.3121865 >> > >> > I don't see a problem. >> > >> > > Hi, >> > > >> > > >> > > When I examine the score calculation of DisMax in Solr, it looks >>to >> > > me that DisMax is using tf x idf^2 instead of tf x idf. >> > > Does anyone have insight why tf x idf is not used here? >> > > >> > > Here is the score contribution from one one field: >> > > >> > > score(q,c) = queryWeight x fieldWeight >> > > >> > > = tf x idf x idf x queryNorm x fieldNorm >> > > >> > > Here is the example that I used to derive the formula above. >>Clearly, >> > > idf is multiplied twice in the score calculation. >> > > * >> > >> > >>http://localhost:8983/solr/select/?q=GB&version=2.2&start=0&rows=10&inden >> > t= >> > >> > > on&debugQuery=true&fl=id,score * >> > > >> > > <str name="6H500F0"> >> > > >> > > 0.18314168 = (MATCH) sum of: >> > > 0.18314168 = (MATCH) weight(text:gb in 1), product of: >> > > 0.35845062 = queryWeight(text:gb), product of: >> > > 2.3121865 = idf(docFreq=6, numDocs=26) >> > > 0.15502669 = queryNorm >> > > >> > > 0.5109258 = (MATCH) fieldWeight(text:gb in 1), product of: >> > > 1.4142135 = tf(termFreq(text:gb)=2) >> > > 2.3121865 = idf(docFreq=6, numDocs=26) >> > > 0.15625 = fieldNorm(field=text, doc=1) >> > > >> > > </str> >> > > >> > > >> > > Thanks!
