updated city connection to avoid city centers

examples/flatland_2_0_example.py

@@ -34,10 +34,10 @@ env = RailEnv(width=50,
               height=50,
               rail_generator=sparse_rail_generator(num_cities=9,  # Number of cities in map (where train stations are)
                                                    num_trainstations=50,  # Number of possible start/targets on map
-                                                   min_node_dist=8,  # Minimal distance of nodes
+                                                   min_node_dist=5,  # Minimal distance of nodes
                                                    node_radius=3,  # Proximity of stations to city center
                                                    seed=15,  # Random seed
-                                                   grid_mode=False,
+                                                   grid_mode=True,
                                                    max_connection_points_per_side=2,
                                                    max_nr_connection_directions=4
                                                    ),

flatland/core/grid/grid4_astar.py

@@ -98,10 +98,11 @@ def a_star(grid_map: GridTransitionMap,
             # create new node
             new_node = AStarNode(node_pos, current_node)
 
-            # Skip paths through forbidden regions.
+            # Skip paths through forbidden regions if they are provided
             if forbidden_cells is not None:
                 if node_pos in forbidden_cells and new_node != start_node and new_node != end_node:
                     continue
+
             children.append(new_node)
 
         # loop through children

flatland/envs/rail_generators.py

@@ -576,7 +576,6 @@ def sparse_rail_generator(num_cities=5, num_trainstations=2, min_node_dist=20, n
             node_positions, city_cells = _generate_node_positions_grid_mode(nb_nodes, height, width)
         else:
             node_positions, city_cells = _generate_node_positions_not_grid_mode(nb_nodes, height, width)
-        print(city_cells)
 
         # reduce nb_nodes, _num_cities, _num_intersections if less were generated in not_grid_mode
         nb_nodes = len(node_positions)