# update theta
    for (n, (f, e)) in enumerate(bitext):
        for f_i in f:
            z = 0
            for e_j in e:
                z += theta[(f_i,e_j)]
            for e_j in e:
                c = theta[(f_i,e_j)] / z
                count[(f_i,e_j)] += c
                single_count[e_j] += c

        for (f_i,e_j) in count.iterkeys():
            theta[(f_i,e_j)] = count[(f_i,e_j)] / single_count[e_j]