                  self.moves.set_valid(self.moves._is_valid, stcls)
                  raise
              cost = guess.get_cost(stcls, &gold.c, guess.label)
              self.model.update(context, guess.clas, best.clas, cost)
              guess.do(stcls, guess.label)
              loss += cost
          return loss
 
</s> remove             best = self.moves.best_gold(scores, stcls, gold)
 </s> add             try:
                best = self.moves.best_gold(scores, stcls, gold)
            except:
                history.append((self.moves.move_name(guess.move, guess.label), '!', stcls.print_state(words)))
                for i, word in enumerate(words):
                    print gold.orig_annot[i]
                print '\n'.join('\t'.join(s) for s in history)
                print words[gold.c.heads[stcls.S(0)]]
                print words[gold.c.heads[stcls.B(0)]]
                print push_cost(stcls, &gold.c, stcls.B(0))
                print arc_cost(stcls, &gold.c, stcls.S(0), stcls.B(0))
                self.moves.set_valid(self.moves._is_valid, stcls)
                raise </s> remove         # When we break, we can't reach any arcs between stack and buffer
        # So cost is number of deps between S0...Sn and B0...Nn
        cdef int cost = 0
        cdef int i, j, B_i, S_i
        for i in range(s.buffer_length()):
            B_i = s.B(i)
            for j in range(s.stack_depth()):
                S_i = s.S(j)
                cost += gold.heads[B_i] == S_i
                cost += gold.heads[S_i] == B_i
        return cost
 </s> add         # Check for sentence boundary --- if it's here, we can't have any deps
        # between stack and buffer, so rest of action is irrelevant.
        s0_root = _get_root(s.S(0), gold)
        b0_root = _get_root(s.B(0), gold)
        if s0_root == -1 or b0_root == -1 or s0_root != b0_root:
            return 0
        else:
            return 1 </s> remove             #print stcls.print_state(words)
 </s> add 
            history.append((self.moves.move_name(guess.move, guess.label), str(cost), stcls.print_state(words)))
                  self.moves.set_valid(self.moves._is_valid, stcls)
                  raise
              cost = guess.get_cost(stcls, &gold.c, guess.label)
            history.append((self.moves.move_name(guess.move, guess.label), str(cost), stcls.print_state(words)))
              self.model.update(context, guess.clas, best.clas, cost)
              guess.do(stcls, guess.label)
              loss += cost
          return loss
keep keep add keep keep keep keep
 * Fixes to unshift/fast-forward strategy. Getting 91.55 greedy on NW dev, gold preproc 
spacy/syntax/parser.pyx