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From "Zeynep P." <>
Subject Re: delete entries from posting list Lucene 4.0
Date Tue, 27 Mar 2012 18:25:18 GMT
While using the pruning package, I realised that ridf is calculated in
RIDFTermPruningPolicy as follows:
Math.log(1 - Math.pow(Math.E, termPositions.freq() / maxDoc)) - df 

However, according to the original paper (Blanco et al.) for residual idf,
it should be -log(df/D) + log (1 - e^(*-*tf/D)). Thus, in the equation,
Math.pow should be Math.pow(Math.E, - (termPositions.freq() / maxDoc))

Do I miss something in the calculation or is this a bug? 

Thanks in advance

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