chebyshev distance added

examples/simple_example_city_railway_generator.py

@@ -17,9 +17,12 @@ if os.path.exists("./../render_output/"):
         np.random.seed(itrials)
 
         # select distance function used in a-star path finding
-        dist_fun = Vec2d.get_euclidean_distance
-        if np.random.choice(1) == 0:
-            dist_fun = Vec2d.get_manhattan_distance
+        dist_fun = Vec2d.get_manhattan_distance
+        dfsel = itrials % 3
+        if dfsel == 1:
+            dist_fun = Vec2d.get_euclidean_distance
+        elif dfsel == 2:
+            dist_fun = Vec2d.get_chebyshev_distance
 
         # create RailEnv and use the city_generator to create a map
         env = RailEnv(width=40 + np.random.choice(100),

flatland/core/grid/grid_utils.py

@@ -71,6 +71,7 @@ class Vec2dOperations:
     def get_norm(node: Vector2D) -> float:
         """
         calculates the euclidean norm of the 2d vector
+        [see: https://lyfat.wordpress.com/2012/05/22/euclidean-vs-chebyshev-vs-manhattan-distance/]
 
         :param node: tuple with coordinate (x,y) or 2d vector
         :return:
@@ -95,6 +96,7 @@ class Vec2dOperations:
     def get_manhattan_distance(node_a: Vector2D, node_b: Vector2D) -> float:
         """
         calculates the manhattan distance of the 2d vector
+        [see: https://lyfat.wordpress.com/2012/05/22/euclidean-vs-chebyshev-vs-manhattan-distance/]
 
         :param node: tuple with coordinate (x,y) or 2d vector
         :return:
@@ -104,6 +106,20 @@ class Vec2dOperations:
         delta = (Vec2dOperations.subtract(node_b, node_a))
         return np.abs(delta[0]) + np.abs(delta[1])
 
+    @staticmethod
+    def get_chebyshev_distance(node_a: Vector2D, node_b: Vector2D) -> float:
+        """
+        calculates the chebyshev norm of the 2d vector
+        [see: https://lyfat.wordpress.com/2012/05/22/euclidean-vs-chebyshev-vs-manhattan-distance/]
+
+        :param node: tuple with coordinate (x,y) or 2d vector
+        :return:
+            -------
+        returns the chebyshev distance
+        """
+        delta = (Vec2dOperations.subtract(node_b, node_a))
+        return max(np.abs(delta[0]), np.abs(delta[1]))
+
     @staticmethod
     def normalize(node: Vector2D) -> Tuple[float, float]:
         """