What is the action mapping when using the full legal action set?

[djbyrne]

I am curious as to how envpool handles actions when using the full action set that are outside the minimal action set for the environment.

For example if a game only uses 8/18 actions, and an action outside of the 8 is given, what does the environment do?

1. is it a No-Op?
2. is the previous action repeated?
3. is there specific mappings from multiple actions to a single action (i.e are all the UPFIRE, LEFTFIRE, DOWNFIRE just mapped to FIRE) ?

If anyone can point me to where this is defined I would greatly appreciate it!

[Trinkle23897]

envpool/envpool/atari/atari_env.h

Line 191 in 51f4686

reward += env_->act(action_set_[act]);

action will be mapped from action_set_, where it's from

envpool/envpool/atari/atari_env.h

Lines 129 to 133 in 51f4686

	if (spec.config["full_action_space"_]) {
	action_set_ = env_->getLegalActionSet();
	} else {
	action_set_ = env_->getMinimalActionSet();
	}

It will use ale's interface, same as https://github.com/mgbellemare/Arcade-Learning-Environment/blob/259f24951d27bdfcb5d7b3f54f1f420ca44b71ef/src/python/env/gym.py#L256

https://github.com/mgbellemare/Arcade-Learning-Environment/blob/259f24951d27bdfcb5d7b3f54f1f420ca44b71ef/src/python/ale_python_interface.hpp#L47-L49