randomized through path found

flatland/envs/rail_generators.py

@@ -768,13 +768,15 @@ def sparse_rail_generator(num_cities=5, grid_mode=False, max_inter_city_rails=4,
         for current_city in range(len(node_positions)):
             all_outer_connection_points = [item for sublist in outer_connection_points[current_city] for item in
                                            sublist]
+            city_boarder = _city_boarder(node_positions[current_city], node_radius)
 
-            for boarder in range(4):
+            random_boarders = np.random.choice(np.arange(4), 4, False)
+            # TODO: Only look at the relevant boarders (Only two at the moment)
+            for boarder in random_boarders:
                 for source in inner_connection_points[current_city][boarder]:
-                    for other_boarder in range(4):
+                    for other_boarder in random_boarders:
                         if boarder != other_boarder and len(inner_connection_points[current_city][other_boarder]) > 0:
                             for target in inner_connection_points[current_city][other_boarder]:
-                                city_boarder = _city_boarder(node_positions[current_city], node_radius)
                                 current_track = connect_cities(rail_trans, grid_map, source, target, city_boarder)
                                 if target in all_outer_connection_points and source in \
                                     all_outer_connection_points and len(through_path_cells[current_city]) < 1: