In the case of the Arabic collection, we observe a strictly decreasing trend for the MAP scores as λ 2 decreases, and the best results are obtained when λ 1 is 0 and λ 2 is 1.0 (call the condition with the best MAP score E).
the interpolation yields a maximum 0.3058 MAP when it was based entirely on P r phrase , ignoring distributions P r token and P r nbest .