The most common approach is an iterative algorithm MERT <cite>[3]</cite> which employs N-best lists (the best N translations decoded with a weight set from a previous iteration) as candidate translations C. In this way, the loss function is constructed as E(Ē,Ê) = S s=1 E(ē s ,ê s ), whereē is the reference sentence,ê is selected from N-best lists byê s = arg max e∈C K k=1 w k H k (e, f s ) and S represents the volume of sentences.