State construction is important for learning in partially observable environments. A general purpose strategy for state construction is to learn the state update using a Recurrent Neural Network (RNN), which updates the internal state using the current internal state and the most recent observation. This internal state provides a summary of the observed sequence, to facilitate accurate predictions and decision-making. At the same time, specifying and training RNNs is notoriously tricky, particularly as the common strategy to approximate gradients back in time, called truncated Back-prop Through Time (BPTT), can be sensitive to the truncation window. Further, domain-expertise—which can usually help constrain the function class and so improve trainability—can be difficult to incorporate into complex recurrent units used within RNNs. In this work, we explore how to use multi-step predictions to constrain the RNN and incorporate prior knowledge. In particular, we revisit the idea of using predictions to construct state and ask: does constraining (parts of) the state to consist of predictions about the future improve RNN trainability? We formulate a novel RNN architecture, called a General Value Function Network (GVFN), where each internal state component corresponds to a prediction about the future represented as a value function. We first provide an objective for optimizing GVFNs, and derive several algorithms to optimize this objective. We then show that GVFNs are more robust to the truncation level, in many cases only requiring one-step gradient updates.

In this paper we show that restricting the representation-layer of a Recurrent Neural Network (RNN) improves accuracy and reduces the depth of recursive training procedures in partially observable domains. Artificial Neural Networks have been shown to learn useful state representations for high-dimensional visual and continuous control domains. If the the tasks at hand exhibits long depends back in time, these instantaneous feed-forward approaches are augmented with recurrent connections and trained with Back-prop Through Time (BPTT). This unrolled training can become computationally prohibitive if the dependency structure is long, and while recent work on LSTMs and GRUs has improved upon naive training strategies, there is still room for improvements in computational efficiency and parameter sensitivity. In this paper we explore a simple modification to the classic RNN structure: restricting the state to be comprised of multi-step General Value Function predictions. We formulate an architecture called General Value Function Networks (GVFNs), and corresponding objective that generalizes beyond previous approaches. We show that our GVFNs are significantly more robust to train, and facilitate accurate prediction with no gradients needed back-in-time in domains with substantial long-term dependences.