addition

The passage around this formula

Reciprocal rank fusion avoids the currency problem by discarding scores altogether and combining rank positions instead. For a document d and a set of ranked result lists R , with r(d) the rank of d in a given list and a smoothing constant k : $\mathrm{RRF}(d) = \sum_{r \in R} \frac{1}{k + r(d)}$. Cormack, Clarke, and Buettcher introduced the method and reported that it consistently outperformed both the individual ranked lists and a Condorcet-style fusion baseline, with the specific virtue that it requires no score normalisation across systems with incompatible scoring functions [ 9 ] . That virtue is also its limitation: two documents ranked first in their respective lists count identically toward the fused score…

Read this part in the article →