1 PROCEDURE (G: proper digraph)
 2 	Let R be a set of vertices
 3 	Let E be a set of edges between layer i and (i+1)
 4 	Let crossings be a integer
 5
 6 	CALL computeBaryCenter with G RETURN R
 7 	Sort R based on barycentric value
 8 	FOR each e in E
 9     Remove e from E
10     FOR each e1 from E
11       crossings = crossings + crossing between e and e1
12     END LOOP
13 	END LOOP
14 END PROCEDURE