The most popular algorithm for this weight optimisation is the line-search based MERT (Och, 2003), but recently other algorithms that support more features, such as PRO (Hopkins and May, 2011) or MIRA-based algorithms (Watanabe et al., 2007;Chiang et al., 2008;Cherry and Foster, 2012), have been introduced.
whilst the differences between promix and perplexity minimisation are not large on the nc test set (about +0.5 BLEU) the results have been demonstrated to apply across many language pairs.