  Program Synthesis is the task of generating a program from a provided
specification. Traditionally, this has been treated as a search problem by the
programming languages (PL) community and more recently as a supervised learning
problem by the machine learning community. Here, we propose a third approach,
representing the task of synthesizing a given program as a Markov decision
process solvable via reinforcement learning(RL). From observations about the
states of partial programs, we attempt to find a program that is optimal over a
provided reward metric on pairs of programs and states. We instantiate this
approach on a subset of the RISC-V assembly language operating on floating
point numbers, and as an optimization inspired by search-based techniques from
the PL community, we combine RL with a priority search tree. We evaluate this
instantiation and demonstrate the effectiveness of our combined method compared
to a variety of baselines, including a pure RL ablation and a state of the art
Markov chain Monte Carlo search method on this task.
