Why are dones in MarkovVectorEnv.step() transformed to int?

[Sam-Amar]

In MarkovVectorEnv.step() dones returned by the parallel env are transformed to numpy.uint8 with the following lines:

dns = np.array(
            [dones.get(agent, False) for agent in self.par_env.possible_agents],
            dtype=np.uint8,
        )

Why is this the case?

This behavior might lead to unexpected consequences.
For example, if we want to do parameter sharing with StableBaselines3, we wrap the parallel env into a MarkovVectorEnv with pettingzoo_env_to_vec_env_v1() and then use concat_vec_envs_v1() as seen in the tutorial. However, if we want to use batch normalization with StableBaselines3.VecNormalize, we get a silent bug, as the line

self.returns[dones] = 0

in VecNormalize.step_wait() then always sets the returns of env_0 to 0 if any done is False.

[benblack769]

Oh, wow, did not realize that sb3 did stuff like that. The reason for this is that the memory layout of np.bool type wasn't super obvious, so to make things a bit less ambiguous, and in the meantime, I decided it would be easier to understand the cross-process data transfer if the data type was uint8.

However, you make a good point that before it is returned to the user, it should probably be converted to a bool.

I think just adding a dones.dtype(bool) to here https://github.com/Farama-Foundation/SuperSuit/blob/master/supersuit/vector/multiproc_vec.py#L208 should solve the issue?