[Feature Proposal] Automatic Selection of Network Type

For beginners, selecting the right policy depending on the environment requires a bit of knowledge (mostly looking at the code of the environment) and this could be simplified by detecting automatically if a CNN or a Mlp policy is needed. In practice, this would translate by passing a "auto" value to the model.

Currently:

from stable_baselines import PPO2

# Images -> CnnPolicy
model = PPO2("CnnPolicy", "BreakoutNoFrameskip-v4")

# Vector obs -> MlpPolicy
model = PPO2("MlpPolicy", "CartPole-v1")

Proposed feature:

from stable_baselines import PPO2
# auto for both cases
model = PPO2("auto", "BreakoutNoFrameskip-v4")
model = PPO2("auto", "CartPole-v1")

Thing I’m not sure: what string to use? “auto”, “autoPolicy”, “autodetect”?

[araffin]

If you prefer the second solution however, it should be done like this:

I feel like this can be simplified. I would also rather do something like:

def __init__(self, policy, env=None, **kwargs):
    if env is not None:
        assert isinstance(env, gym.Env), "the 'env' argument must be a gym.Env"
        # Check on the policy are as in previous versions
    else:
        assert isinstance(policy, gym.Env), "When the 'env' argument not is given, the first argument must be a gym.Env"
        env = policy
        policy = None
    
    if policy is None:
        # TODO: autodetect

[araffin]

After thinking again about that feature, this could be nice to have for the user but would obfuscate the code, the best way would be to have function overload… So I’m removing it from the roadmap for now.