fixed grid mode. Now if parameter is set too high it will not build those cities

examples/flatland_2_0_example.py

@@ -30,9 +30,9 @@ speed_ration_map = {1.: 0.25,  # Fast passenger train
                     1. / 3.: 0.25,  # Slow commuter train
                     1. / 4.: 0.25}  # Slow freight train
 
-env = RailEnv(width=75,
-              height=75,
-              rail_generator=sparse_rail_generator(max_num_cities=50,
+env = RailEnv(width=30,
+              height=30,
+              rail_generator=sparse_rail_generator(max_num_cities=4,
                                                    # Number of cities in map (where train stations are)
                                                    seed=1,  # Random seed
                                                    grid_mode=True,

flatland/envs/rail_generators.py

@@ -649,9 +649,9 @@ def sparse_rail_generator(max_num_cities: int = 5, grid_mode: bool = False, max_
                                               vector_field) -> (IntVector2DArray, IntVector2DArray):
         aspect_ratio = height / width
         cities_per_row = min(int(np.ceil(np.sqrt(num_cities * aspect_ratio))),
-                             int((height - 2 * (city_radius + 1)) / (2 * city_radius + 1)))
+                             int((height - 2) / (2 * city_radius + 1)))
         cities_per_col = min(int(np.ceil(num_cities / cities_per_row)),
-                             int((width - 2 * (city_radius + 1)) / (2 * city_radius + 1)))
+                             int((width - 2) / (2 * city_radius + 1)))
         num_build_cities = min(num_cities, cities_per_col * cities_per_row)
         row_positions = np.linspace(city_radius + 1, height - 2 * (city_radius + 1), cities_per_row, dtype=int)
         col_positions = np.linspace(city_radius + 1, width - 2 * (city_radius + 1), cities_per_col, dtype=int)