BUG: Nondeterminisitc behaviour of MetaDriveEnv

[PanZWarzywniaka]

Hi MetaDrive team,

I believe I discovered a bug, in resetting the MetaDriveEnv resulting in nondeterminism.

MetaDrive simulation supposed to be deterministic but even when I use the enviroment and reset it with same with same seed resulting traces are not identical. Cosider following code adapted from examples:

try:
    env=MetaDriveEnv(config={"map":"C",
                            "num_scenarios": n_scenarios})

    for rep in range(n_scenarios):
        obs, step_info = env.reset(seed)
        while True:
            # get action from expert driving, or a dummy action
            action = expert(env.agent, deterministic=True) if expert_driving else [0, 0.33]
            obs, reward, tm, tr, step_info = env.step(action)
            traces.append(step_info)
            
            if tm or tr:
                break
finally:
    env.close()

When I was analyzing traces (step info for each timestep) from diffrent repetitions I found slight diffrences probably comming from floating point number arithemtic. Those diffrences (error) between traces is magnified, the longer the episode is.

Suspecting that .reset() function doesn't clear the state properly I started initializing the enviroment for each repetition, and closing at the end.

try:

    for rep in range(n_scenarios):
        env=MetaDriveEnv(config={"map":"C",
                                "num_scenarios": n_scenarios})
        obs, step_info = env.reset(seed)
        while True:
            
            # get action from expert driving, or a dummy action
            action = expert(env.agent, deterministic=True) if expert_driving else [0, 0.33]
            obs, reward, tm, tr, step_info = env.step(action)
            if tm or tr:
                break

        env.close()
finally:
    pass

Above solved an issue and each traces produced are exacly the same (fully deterministic).

Please see my notebook reproducing the bug.

Conda env

# This file may be used to create an environment using:
# $ conda create --name <env> --file <this file>
# platform: linux-64
@EXPLICIT
https://repo.anaconda.com/pkgs/main/linux-64/_libgcc_mutex-0.1-main.conda
https://conda.anaconda.org/conda-forge/linux-64/ca-certificates-2024.7.4-hbcca054_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/ld_impl_linux-64-2.38-h1181459_1.conda
https://repo.anaconda.com/pkgs/main/linux-64/libstdcxx-ng-11.2.0-h1234567_1.conda
https://repo.anaconda.com/pkgs/main/noarch/tzdata-2024a-h04d1e81_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/libgomp-11.2.0-h1234567_1.conda
https://repo.anaconda.com/pkgs/main/linux-64/_openmp_mutex-5.1-1_gnu.conda
https://repo.anaconda.com/pkgs/main/linux-64/libgcc-ng-11.2.0-h1234567_1.conda
https://repo.anaconda.com/pkgs/main/linux-64/bzip2-1.0.8-h5eee18b_6.conda
https://repo.anaconda.com/pkgs/main/linux-64/libffi-3.4.4-h6a678d5_1.conda
https://conda.anaconda.org/conda-forge/linux-64/libsodium-1.0.18-h36c2ea0_1.tar.bz2
https://repo.anaconda.com/pkgs/main/linux-64/libuuid-1.41.5-h5eee18b_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/ncurses-6.4-h6a678d5_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/openssl-3.0.14-h5eee18b_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/xz-5.4.6-h5eee18b_1.conda
https://repo.anaconda.com/pkgs/main/linux-64/zlib-1.2.13-h5eee18b_1.conda
https://repo.anaconda.com/pkgs/main/linux-64/readline-8.2-h5eee18b_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/tk-8.6.14-h39e8969_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/zeromq-4.3.5-h6a678d5_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/sqlite-3.45.3-h5eee18b_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/python-3.10.14-h955ad1f_1.conda
https://repo.anaconda.com/pkgs/main/linux-64/debugpy-1.6.7-py310h6a678d5_0.conda
https://conda.anaconda.org/conda-forge/noarch/decorator-5.1.1-pyhd8ed1ab_0.tar.bz2
https://conda.anaconda.org/conda-forge/noarch/entrypoints-0.4-pyhd8ed1ab_0.tar.bz2
https://conda.anaconda.org/conda-forge/noarch/exceptiongroup-1.2.2-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/executing-2.0.1-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/nest-asyncio-1.6.0-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/packaging-24.1-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/parso-0.8.4-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/pickleshare-0.7.5-py_1003.tar.bz2
https://conda.anaconda.org/conda-forge/noarch/platformdirs-4.2.2-pyhd8ed1ab_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/psutil-5.9.0-py310h5eee18b_0.conda
https://conda.anaconda.org/conda-forge/noarch/ptyprocess-0.7.0-pyhd3deb0d_0.tar.bz2
https://conda.anaconda.org/conda-forge/noarch/pure_eval-0.2.3-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/pygments-2.18.0-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/linux-64/python_abi-3.10-2_cp310.tar.bz2
https://repo.anaconda.com/pkgs/main/linux-64/pyzmq-25.1.2-py310h6a678d5_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/setuptools-72.1.0-py310h06a4308_0.conda
https://conda.anaconda.org/conda-forge/noarch/six-1.16.0-pyh6c4a22f_0.tar.bz2
https://conda.anaconda.org/conda-forge/noarch/traitlets-5.14.3-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/typing_extensions-4.12.2-pyha770c72_0.conda
https://conda.anaconda.org/conda-forge/noarch/wcwidth-0.2.13-pyhd8ed1ab_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/wheel-0.43.0-py310h06a4308_0.conda
https://conda.anaconda.org/conda-forge/noarch/asttokens-2.4.1-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/comm-0.2.2-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/jedi-0.19.1-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/linux-64/jupyter_core-5.7.2-py310hff52083_0.conda
https://conda.anaconda.org/conda-forge/noarch/matplotlib-inline-0.1.7-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/pexpect-4.9.0-pyhd8ed1ab_0.conda
https://repo.anaconda.com/pkgs/main/linux-64/pip-24.2-py310h06a4308_0.conda
https://conda.anaconda.org/conda-forge/noarch/prompt-toolkit-3.0.47-pyha770c72_0.conda
https://conda.anaconda.org/conda-forge/noarch/python-dateutil-2.9.0-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/linux-64/tornado-6.1-py310h5764c6d_3.tar.bz2
https://conda.anaconda.org/conda-forge/noarch/jupyter_client-7.3.4-pyhd8ed1ab_0.tar.bz2
https://conda.anaconda.org/conda-forge/noarch/stack_data-0.6.2-pyhd8ed1ab_0.conda
https://conda.anaconda.org/conda-forge/noarch/ipython-8.26.0-pyh707e725_0.conda
https://conda.anaconda.org/conda-forge/noarch/ipykernel-6.29.5-pyh3099207_0.conda