[RLlib] Issue 8319 DDPG (MA or num_envs_per_worker > 1) broken. (#8324)

rllib/examples/env/simple_corridor.py

@@ -12,24 +12,21 @@ class SimpleCorridor(gym.Env):
         self.end_pos = config["corridor_length"]
         self.cur_pos = 0
         self.action_space = Discrete(2)
-        self.observation_space = Box(
-            0.0, self.end_pos, shape=(1, ), dtype=np.float32)
+        self.observation_space = Box(0.0, 999.0, shape=(1, ), dtype=np.float32)
 
     def set_corridor_length(self, length):
         self.end_pos = length
-        self.observation_space = Box(
-            0.0, self.end_pos, shape=(1, ), dtype=np.float32)
         print("Updated corridor length to {}".format(length))
 
     def reset(self):
-        self.cur_pos = 0
+        self.cur_pos = 0.0
         return [self.cur_pos]
 
     def step(self, action):
         assert action in [0, 1], action
         if action == 0 and self.cur_pos > 0:
-            self.cur_pos -= 1
+            self.cur_pos -= 1.0
         elif action == 1:
-            self.cur_pos += 1
+            self.cur_pos += 1.0
         done = self.cur_pos >= self.end_pos
         return [self.cur_pos], 1 if done else 0, done, {}