BM25

Creator
Creator
Seonglae Cho
Created
Created
2023 Sep 19 15:28
Editor
Edited
Edited
2025 Jan 29 13:2

TF-IDF
+ passage length

Two Poisson model
검색엔진, 추천 시스템 등에서 아직까지도 많이 사용되는 알고리즘
BM25(D,Q)=wQIDF(w)f(w,D)(k1+1)f(w,D)+k1(1b+bDavgDL) \text{BM25}(D, Q) = \sum_{w \in Q} \frac{IDF(w) \cdot f(w, D) \cdot (k_1 + 1)}{f(w, D) + k_1 \cdot (1 - b + b \cdot \frac{|D|}{\text{avgDL}})} 
 
 

BM25+
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based on
Contingency Table

S(D)=iQlog(ri+0.5)/(Rri+0.5)(niri+0.5)/(NniR+ri+0.5)(k1+1)fiK+fi(k2+1)qfik2+qfiS(D) = \sum_{i \in Q} \log \frac{(r_i + 0.5) / (R - r_i + 0.5)}{(n_i - r_i + 0.5) / (N - n_i - R + r_i + 0.5)} \cdot \frac{(k_1 + 1) f_i}{K + f_i} \cdot \frac{(k_2 + 1) q f_i}{k_2 + q f_i}
 
 
 
 
 

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