At the last part of this section we therefore present a simple, O(n) time, local enhancement procedure, that improves the score of the directed tree generated from the output of the undirected MST parser with respect to the edge scores of a standard directed MST parser.
our procedure improves the output of the undirected MST parser with respect to a directed model without having to compute the MST of the latter, which would take O(n 2 ) time.