minor changes

examples/flatland_2_0_example.py

@@ -32,8 +32,8 @@ speed_ration_map = {1.: 0.25,  # Fast passenger train
 
 env = RailEnv(width=50,
               height=50,
-              rail_generator=sparse_rail_generator(num_cities=50,  # Number of cities in map (where train stations are)
-                                                   seed=0,  # Random seed
+              rail_generator=sparse_rail_generator(num_cities=10,  # Number of cities in map (where train stations are)
+                                                   seed=1,  # Random seed
                                                    grid_mode=False,
                                                    max_inter_city_rails=2,
                                                    max_tracks_in_city=4,

flatland/envs/rail_env.py

@@ -248,6 +248,7 @@ class RailEnv(Environment):
                     rc_pos = (r, c)
                     check = self.rail.cell_neighbours_valid(rc_pos, True)
                     if not check:
+                        print(self.rail.grid[rc_pos])
                         warnings.warn("Invalid grid at {} -> {}".format(rc_pos, check))
         # TODO https://gitlab.aicrowd.com/flatland/flatland/issues/172
         #  hacky: we must re-compute the distance map and not use the initial distance_map loaded from file by