The episode terminates when an agent discovers all objects in the sequence of the current episode or when it calls an incorrect FOUND action. A FOUND action is incorrect if it is called when the agent is not within a 1.5m Euclidean distance from its current target object. Note that this does not require the agent to be viewing the object at the time of calling FOUND. After the episode terminates, the agent is evaluated using the Progress and PPL metrics that are defined below.
Progress: The proportion of objects correctly found in the episode.
PPL: Progress weighted by path length. PPL quantifies the efficiency of agent's trajectory with respect to the optimal trajectory.