I created an OpenAI Gym environment, and I would like to check the performance of the agent from OpenAI Baselines DQN approach on it. In my environment, the best possible outcome for the agent is 0 - the robot needs zero non-necessary resources to complete a task. The goal is to minimize the need for resources: for each needed ressource, there is a penalty of -1. In many states, only certain actions make physical sense. How do I deal with this?
There was already a question about the handling of invalid moves on AI StackExchange, recommending to ignore the invalid moves. However, ignoring them would imply returning the same state and a 0 reward, the best possible outcome, which is clearly not the case. Setting drastic negative rewards also does not seem to work, since even promising handling paths are compromised by invalid actions and the corresponding drastic negative reward.
What are other ways of handling invalid actions in scenarios where all rewards are either 0 (best), or negative?
My ideas/ questions on this for the OpenAI Baselines DQN approach implementation
1) Is there any way to set the initial Q-values for the actions? I could set -infinity for the invalid actions. 2) Is there any way to limit the set of valid actions per state? When after the env.step(action) function the new state is returned, can I somehow define which actions are valid for it?