replace boolean global numpy array with int numpy array where the agent handle...

replace boolean global numpy array with int numpy array where the agent handle is set inside the numpy array (#271)

flatland/envs/rail_env.py

@@ -219,8 +219,9 @@ class RailEnv(Environment):
 
         self.valid_positions = None
 
-        # global numpy array of agents position, True means that there is an agent at that cell
-        self.agent_positions: np.ndarray = np.full((height, width), False)
+        # global numpy array of agents position, -1 means that the cell is free, otherwise the agent handle is placed
+        # inside the cell
+        self.agent_positions: np.ndarray = np.zeros((height, width), dtype=int) - 1
 
     def _seed(self, seed=None):
         self.np_random, seed = seeding.np_random(seed)
@@ -362,7 +363,7 @@ class RailEnv(Environment):
             else:
                 self._max_episode_steps = self.compute_max_episode_steps(width=self.width, height=self.height)
 
-        self.agent_positions = np.full((self.height, self.width), False)
+        self.agent_positions = np.zeros((self.height, self.width), dtype=int) - 1
 
         self.restart_agents()
 
@@ -663,7 +664,7 @@ class RailEnv(Environment):
         new_position: IntVector2D
         """
         agent.position = new_position
-        self.agent_positions[agent.position] = True
+        self.agent_positions[agent.position] = agent.handle
 
     def _move_agent_to_new_position(self, agent: EnvAgent, new_position: IntVector2D):
         """
@@ -676,8 +677,8 @@ class RailEnv(Environment):
         new_position: IntVector2D
         """
         agent.position = new_position
-        self.agent_positions[agent.old_position] = False
-        self.agent_positions[agent.position] = True
+        self.agent_positions[agent.old_position] = -1
+        self.agent_positions[agent.position] = agent.handle
 
     def _remove_agent_from_scene(self, agent: EnvAgent):
         """
@@ -688,7 +689,7 @@ class RailEnv(Environment):
         -------
         agent: EnvAgent object
         """
-        self.agent_positions[agent.position] = False
+        self.agent_positions[agent.position] = -1
         if self.remove_agents_at_target:
             agent.position = None
             agent.status = RailAgentStatus.DONE_REMOVED
@@ -753,7 +754,7 @@ class RailEnv(Environment):
             is the cell free or not?
 
         """
-        return not self.agent_positions[position]
+        return self.agent_positions[position] == -1
 
     def check_action(self, agent: EnvAgent, action: RailEnvActions):
         """