fixed bug in step function. Now checking if cell is free before moving out of...

fixed bug in step function. Now checking if cell is free before moving out of cell into the next one.

flatland/envs/rail_env.py

@@ -191,7 +191,8 @@ class RailEnv(Environment):
         # for i in range(len(self.agents_handles)):
         for iAgent in range(self.get_num_agents()):
             agent = self.agents[iAgent]
-
+            if iAgent % 2 == 0:
+                agent.speed_data["speed"] = 1./3.
             if self.dones[iAgent]:  # this agent has already completed...
                 continue
 
@@ -269,7 +270,7 @@ class RailEnv(Environment):
                 agent.speed_data['position_fraction'] += agent.speed_data['speed']
 
             if agent.speed_data['position_fraction'] >= 1.0:
-                agent.speed_data['position_fraction'] = 0.0
+
 
                 # Perform stored action to transition to the next cell
 
@@ -277,10 +278,15 @@ class RailEnv(Environment):
                 # the cell
                 cell_isFree, new_cell_isValid, new_direction, new_position, transition_isValid = \
                     self._check_action_on_agent(agent.speed_data['transition_action_on_cellexit'], agent)
-                agent.old_direction = agent.direction
-                agent.old_position = agent.position
-                agent.position = new_position
-                agent.direction = new_direction
+
+                if all([new_cell_isValid, transition_isValid, cell_isFree]):
+                    agent.old_direction = agent.direction
+                    agent.old_position = agent.position
+                    agent.position = new_position
+                    agent.direction = new_direction
+                    agent.speed_data['position_fraction'] = 0.0
+
+
 
             if np.equal(agent.position, agent.target).all():
                 self.dones[iAgent] = True