This is different for the conditional models, which are easier to handle but where most approaches are based on initializing from single-word based models (Brown et al., 1993;Vogel et al., 1996;Al-Onaizan et al., 1999).
our comparison of projected gradient descent (PGD) and expectation maximization (EM) revealed that EM leads to better alignments, although PGD finds a comparable but slightly higher objective value.