▲ | imtringued 2 days ago | |
Model based reinforcement learning is a thing and it is kind of a crazy idea. Look up temporal difference model predictive control. The fundamental idea behind temporal difference is that you can record any observable data stream over time and predict the difference between past and present based on your decision variables (e.g. camera movement, actuator movement, and so on). Think of it like the Minecraft clone called Oasis AI. The AI predicts the response to a user provided action. Now imagine if it worked as presented. The data problem would be solved, because you are receiving a constant stream of data every single second. If anything, the RL algorithms are nowhere near where they need to be and continual learning has not been solved yet, but the best known way is through automatic continual learning ala Schmidhuber (co-inventor of LSTMs along with Hochreiter). So, model based control is solved right? Everything that can be observed can be controlled once you have a model! Wrong. Unfortunately. You still need the rest of reinforcement learning: an objective and a way to integrate the model. It turns out that reconstructing the observations is too computationally challenging and the standard computational tricks like U-Nets learn a latent representation that is optimized for reconstruction rather than for your RL objectives. There is a data exchange problem that can only realistically be solved by throwing an even bigger model at it, but here is why that won't work either: Model predictive control tries to find the best trajectory over a receding horizon. It is inherently future oriented. This means that you need to optimize through your big model and that is expensive to do. So you're going to have to take shortcuts by optimizing for a specific task. You reduce the dimension of the latent space and stop reconstructing the observations. The price? You are now learning a latent space for your particular task, which is less demanding. The dream of continual learning with infinite data shatters and you are brought down to earth: it's better than what came before, but not that much better. |