Fix/deterministic action space sampling in SubprocVectorEnv (#1103)

test/base/test_action_space_sampling.py

@@ -0,0 +1,57 @@
+import gymnasium as gym
+
+from tianshou.env import DummyVectorEnv, ShmemVectorEnv, SubprocVectorEnv
+
+
+def test_gym_env_action_space() -> None:
+    env = gym.make("Pendulum-v1")
+    env.action_space.seed(0)
+    action1 = env.action_space.sample()
+
+    env.action_space.seed(0)
+    action2 = env.action_space.sample()
+
+    assert action1 == action2
+
+
+def test_dummy_vec_env_action_space() -> None:
+    num_envs = 4
+    envs = DummyVectorEnv([lambda: gym.make("Pendulum-v1") for _ in range(num_envs)])
+    envs.seed(0)
+    action1 = [ac_space.sample() for ac_space in envs.action_space]
+
+    envs.seed(0)
+    action2 = [ac_space.sample() for ac_space in envs.action_space]
+
+    assert action1 == action2
+
+
+def test_subproc_vec_env_action_space() -> None:
+    num_envs = 4
+    envs = SubprocVectorEnv([lambda: gym.make("Pendulum-v1") for _ in range(num_envs)])
+    envs.seed(0)
+    action1 = [ac_space.sample() for ac_space in envs.action_space]
+
+    envs.seed(0)
+    action2 = [ac_space.sample() for ac_space in envs.action_space]
+
+    assert action1 == action2
+
+
+def test_shmem_vec_env_action_space() -> None:
+    num_envs = 4
+    envs = ShmemVectorEnv([lambda: gym.make("Pendulum-v1") for _ in range(num_envs)])
+    envs.seed(0)
+    action1 = [ac_space.sample() for ac_space in envs.action_space]
+
+    envs.seed(0)
+    action2 = [ac_space.sample() for ac_space in envs.action_space]
+
+    assert action1 == action2
+
+
+if __name__ == "__main__":
+    test_gym_env_action_space()
+    test_dummy_vec_env_action_space()
+    test_subproc_vec_env_action_space()
+    test_shmem_vec_env_action_space()

tianshou/env/worker/subproc.py

@@ -126,6 +126,7 @@ def _encode_obs(
                 if hasattr(env, "seed"):
                     p.send(env.seed(data))
                 else:
+                    env.action_space.seed(seed=data)
                     env.reset(seed=data)
                     p.send(None)
             elif cmd == "getattr":